vegetation and building facades

Centre for Sustainability of the Built Environment

CCaassee SSttuuddyy RReeppoorrtt

VVeeggeettaattiioonn oonn bbuuiillddiinngg ffaaccaaddeess:: ‘‘BBiioosshhaaddeerr’’

www.durabuild.org


Executive summary

Plant cover on the external wall has long been used for its decorative and thermal

effects. Plants on walls can assist in cooling buildings in summer as they provide

shading that reduces solar gains to the building. The effect of transpiration by plants

can also extract heat from the surrounding air. Previous studies showed that

vegetation could establish cooler microclimate, thus lower the temperatures around

the buildings and reduce the requirement for cooling in the summer.

In response to the growing awareness of the environmental impact of buildings,

there is an emerging architectural design aims to regulate a building’s indoor

environment by making use of the local climate and natural renewable resources.

Such kind of design is often referred to as ‘bioclimatic’ as its principles are inspired

by the nature. One of the bioclimatic design options is to grow vegetation on

buildings to reduce the summer cooling load and to improve the surrounding air

quality. Although this kind of vegetative building design has been adapted in

traditional masonry buildings, it is unsuitable for modern buildings that use light

weight metal or glazed external claddings.

This case study investigates the applications of deciduous climbing plants as

climatic modifiers. Experiments are being carried out to measure the thermal

shading performance of a vertical layer of deciduous climbing plant canopy. The

deciduous climbing plants are trailed on a metal framework which is mounted

external to the glazed facade of a naturally ventilated building. This so-called

‘bioshader’ provides some distinct advantages over conventional shading devices

such as its foliage shades the building from excessive summer solar gains, the

shedding of leaves in the winter allows beneficial solar heat gains, improvement in

air quality and aesthetic enhancement of the surrounding.

An experiment was setup in two university offices. Bioshader was installed external

to the test room and the external and internal environmental parameters were

monitored. Temperature and relative humidity improvements made by the bioshader

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were reported. Measured solar radiation data were used to determine the solar

transmittances of single and multi-layers of leaf.

There is very a limited research work on how deciduous climbing plant can affect

the internal thermal environment of naturally ventilated buildings. This case study

reviews the current status of using vegetation with buildings, and discusses the

criteria and selection procedure for suitable plants in this area. The types of building

and design features, including the support structures, suitable for applying

deciduous plant are also examined. This case study will help to understanding the

use of vegetation as a means of solar shading to improve the internal environment

for the better comfort of occupants.



Table of contents

Executive summary.................................................................................................. 2

Table of contents...................................................................................................... 4

List of Figures........................................................................................................... 6

List of Tables ............................................................................................................ 7

List of Equation ........................................................................................................ 7

1.0 Introduction.................................................................................................... 8

1.1 Aim ............................................................................................................................................9

1.2 Objectives..................................................................................................................................9

1.3 Report Structure......................................................................................................................10

2.0 Review of vegetation and buildings........................................................... 11

2.1 Trees .......................................................................................................................................12

2.2 Vertical landscaping ................................................................................................................13

2.3 Climbing plants........................................................................................................................14

2.3.1 Climbing patterns .......................................................................................................15

2.3.2 Training systems for climbers ....................................................................................17

2.3.3 List of climbing plants.................................................................................................18

3.0 Energy savings ............................................................................................ 20

4.0 Plant application examples......................................................................... 23

5.0 Bioshader Experiment................................................................................. 27

5.1 Plant selection for bioshader experiment................................................................................28

5.1.1 Plant Selection Criteria ..............................................................................................28

5.1.2 Plants suitable for the United Kingdom climate .........................................................29

5.2 Experimental setup .................................................................................................................29



5.2.1 The Site......................................................................................................................30

5.2.2 Plant and External Framework ..................................................................................31

5.2.3 Measuring Equipment ................................................................................................32

6.0 Results.......................................................................................................... 35

6.1 Data Selection.........................................................................................................................35

6.2 Temperature Comparison .......................................................................................................35

6.3 Relative Humidity Comparison................................................................................................36

6.4 Leaf Solar Transmittance ........................................................................................................38

7.0 Discussion and Analysis............................................................................. 40

7.1 Temperatures and Relative Humidities...................................................................................40

7.2 Effect of solar reduction by leaves ..........................................................................................43

7.3 Limitation to bioshader experiment .........................................................................................44

8.0 Conclusion ................................................................................................... 46

9.0 Bibliography................................................................................................. 48

10.0 Appendix ...................................................................................................... 51

Appendix A: Solar adjustment for vertically fixed sensors...................................................................51

Appendix B: Graphs for leaf solar transmittances ...............................................................................55



List of Figures

Figure 1: Good reasons for façade greening (Pictures from Jakob Inox Green Solutions G1 catalogue) ..............................................................................................................................................8 Figure 2: Plants used to cool and shade the cafeteria in Spain. Picture taken from (Crosbie, 1994) ...9 Figure 3: The red rose plant adds decent colour to the building. Picture obtained from (Tredici, 1994).............................................................................................................................................................12 Figure 4: Singapore Exhibition Tower model and the vertical landscaping on the right. Picture taken from (Davey, 1999) ..............................................................................................................................14 Figure 6: Hedera helix with clinging stem roots (Fassadengrün) ........................................................16 Figure 8: Vitis Coignetiae or grape vine (Gillian, 2000) .......................................................................16 Figure 11: Surface temperature difference of wall with and without shading. Graph taken from (Parker, 1983) ....................................................................................................................................................20 Figure 13: Credomatic Call Centre designed by Bruno Stagno. Picture provided by Bruno Stagno ..24 Figure 14: Light filters through the green wall into the office interior if the Consorcio-Santiago Building. Photographer: Guy Wenborne. Pictures provided by Enrique Browne ...............................................25 Figure 17: A vertical section through the bioshader system (Ip et al., 2004) ......................................27 Figure 19: The details of the stainless steel framework.......................................................................31 Figure 20: The Virginia Creeper trained onto the framework and the plant containers.......................32 Figure 21: Plan showing locations of monitoring equipment ...............................................................32 Figure 22: Cross section of the bioshader with the locations of sensors ............................................33 Figure 23: Temperature distributions on 13th July 2003 .....................................................................35 Figure 24: Temperature distributions on 20th July 2003 .....................................................................35 Figure 25: Temperature distributions on 10th Aug 2003 .....................................................................36 Figure 26: Temperature distributions on 24th Aug 2003 .....................................................................36 Figure 27: Temperature distributions on 21st Sept 2003 ....................................................................36 Figure 28: Temperature distributions on 28th Sept 2003 ....................................................................36 Figure 29: Temperature distributions on 12th Oct 2003 ......................................................................36 Figure 30: Temperature distributions on 26th Oct 2003 ......................................................................36 Figure 31: Relative humidity 13th July 2003........................................................................................37 Figure 32: Relative humidity 27th July 2003........................................................................................37 Figure 33: Relative humidity 10th Aug 2003........................................................................................37 Figure 34: Relative humidity 24th Aug 2003........................................................................................37 Figure 35: Relative humidity 21st Sept 2003 .......................................................................................37 Figure 36: Relative humidity 28th Sept 2003.......................................................................................37 Figure 37: Relative humidity distributions on 12th Oct2003 ................................................................37 Figure 38: Relative humidity distributions on 26th Oct2003 ................................................................37 Figure 39: One layer of leaf covering the solar flux sensor for the determination of single-leaf solar transmittance........................................................................................................................................38 Figure 40: Bioshader reduced room temperature to comfort range ....................................................41



Figure 41: Temperature profiles of test room, control room in August ................................................42 Figure 42: Solar transmittance for 1-layer of Virginia Creeper leaf .....................................................55 Figure 43: Solar transmittance for 2-layers of Virginia Creeper leaf....................................................55 Figure 44: Solar transmittance for 3-layers of Virginia Creeper leaf....................................................56 Figure 45: Solar transmittance for 4-layers of Virginia Creeper leaf....................................................56 Figure 46: Solar transmittance for 5-layers of Virginia Creeper leaf....................................................57

List of Tables

Table 1: Popular types of climbing plants ............................................................................................19 Table 2: Summary of experiments and results of relevant researches (Lam et al., 2003) ..................22 Table 3: Selection criteria of climbing plants for use as bioshaders (Lam et al., 2002) ......................28 Table 4: Summary of climbers in their order of their suitability for use as bioshader in the southern part of the United Kingdom. Based on plant characteristics described in (Brickell, 1999, Chesshire, 2001) ....................................................................................................................................................29 Table 5: The mean solar transmittances of one to five layers of Virginia Creeper leaf .......................39 Table 6: Peak difference temperatures (°C) between test and control rooms on selected Sundays ..40 Table 7: Peak differences in relative humidity between test and control rooms.................................43 Table 8: Solar reduction by Virginia Creeper leaves ...........................................................................44

List of Equation

II

TExtn

n = (Equation 1: Leaf solar transmittance)..................................................................38



1.0 Introduction

With the increasing concern of the global energy crisis, designers and researchers are urged to find

sustainable alternatives to reduce the energy consumption throughout the life cycle of the building.

Almost 50% of the UK’s energy consumption and carbon dioxide emissions are attributed to the

building’s operation (Parrott, 1998). The energy usage during the operational phase of the building’s

life cycle is often most significant, of which the vast energy is consumed on heating and cooling for

occupants’ thermal comfort. About 55% of the total energy consumptions in buildings are used for

space heating and cooling (DTI, 2002).

The progressing global climate change has created hotter summers and cooler winters. The

emerging heat waves in the summer cause people to inhabit in unbearable weather conditions.

Building occupants need to increase the demand for space cooling in order to maintain the required

internal thermal comfort. This would result in a conflict between reducing air-conditioning energy

consumption and maintaining an acceptable thermal comfort condition during hot weathers.

Excessive summer solar gains often causes overheating in buildings and thermal discomfort to

occupants. One commonly used option to reduce solar gains is to introduce solar shading.

Conventional shading devices such as sun blinds, sunscreens, awnings, projections etc. are

examples. Recently there is a growing interest in using vegetation as shading devices. Comparative

studies of using plants and conventional shading devices as passive solar control systems have been

conducted by a number of researchers (Hoyano, 1988, Papadakis et al., 2001, Stec and Paassen,

2005). Results showed that plants offered some significant advantages over conventional shading

devices such as lower surface plant temperature and higher relative humidity of air shaded by plants.

This is mainly due to the ability of vegetation to dissipate absorbed solar radiation into sensible and

latent heat through the process of evapo-transpiration. It was observed that about 60% of the

absorbed radiation can be converted to latent heat in plants (Stec and Paassen, 2005).

Figure 1: Good reasons for façade greening (Pictures from Jakob Inox Green Solutions G1 catalogue)



The current trend to use natural ventilation tor conserve natural resources is also a big drive to

incorporate greenery in buildings. Bioclimatic building design is a developing passive architectural

design which takes advantage of the local climate and natural resources to provide indoor comfort to

the building occupants. One commonly used bioclimatic design option is the growing of vegetation on

buildings to regulate the microclimate of the building’s external and internal environment.

Figure 2: Plants used to cool and shade the cafeteria in Spain. Picture taken from (Crosbie, 1994)

Applying vegetation around buildings is appealing and ecologically sensible. There are numerous

good reasons for greening. The most obvious benefit of having green facades is the regulation of

internal temperatures. The familiar pergola, as seen in Figure 2, in southern countries is a very

effective method of internal temperature regulation. It promotes the formation of an insulating layer of

air, thereby preventing an excessive increase of the inside temperature due to direct solar radiation

(Jakob, 2003). This principle also offers several advantages when applied to vertical structures: the

insulating cushion of air between vegetation and façade evens out temperature fluctuations and

noticeably reduces heating and air-conditioning costs.

A well-designed covering of vegetation is a natural shield against rain and ultraviolet radiation. In

addition, the space between the façade and the greenery has a temperature regulating effect and

promotes optimum ventilation as well. The aesthetics of greening that brings to occupants is also a

great advantage. The integration of greened surfaces into contemporary architecture presents novel

opportunities and promotes energy efficiency in buildings.

1.1 Aim

The aim of this case study is to evaluate the thermal performance of deciduous climbing plants used

as external building shading devices

1.2 Objectives

The objectives of this case study include:

• To give an overview on the use of vegetation with buildings



• To report on previous works on energy savings contributed by vegetation

• To give examples of vegetated buildings

• To present research results on using plants as external shading devices (termed as

‘bioshader’)

• To evaluate the performance of the bioshader

1.3 Report Structure

This case study report focuses on the applications of how vegetation is incorporated in the building

design, with particular attention to the use of greenery on building facades. An in-depth literature

review was performed with a summary on predicted energy savings performed by other researchers.

A number of current building examples which integrated vegetation in their designs are described in

this report. Further investigation was carried out on evaluating the performance of a plant shading

device termed as ‘bioshader’. This bioshader is the use of climbing deciduous plants to act as

shading devices over a building’s glazed areas. Details of the design were described and the

experimental setup was reported. Measurements of the experiment were taken and results were

analysed.



2.0 Review of vegetation and buildings

Leaf cover on the external walls has long been used for its decorative and thermal effects. During the

pioneering days of study of the thermal performance of buildings, Van Straaten (1967) (Straaten,

1967)wrote:

It must also be remembered that in situations where shade in summer and sun in winter is required,

deciduous trees, shrubs and creepers will often provide a convenient and cheap solution.

Thirteen years later, Parker (1980) (Parker, 1980) found out that:

Although using vegetation to cool a space is not a new concept; many recent attempts to build

energy-efficient buildings have totally ignored its significance. The primary reason for this omission is

the lack of detailed quantitative data as to how effective vegetation is in reducing the energy used in

heating and cooling a place. In addition, many of the recommendations for energy-conserving

landscape design concepts have not been verified through actual experimentation.

There is a widespread belief in the past that plants are inimical to built structures, ripping out the

mortar and prising apart joints with their roots. The evidence suggests that only where decay has

already set in and then plants can indeed accelerate the process of deterioration. Certainly little

evidence shows that plants will actually damage building walls. In some cases, the plants covering

the wall are acting as a protective layer to the wall from the elements. Furthermore, a layer of

vegetation which protects a building from solar radiation may greatly reduce the thermal tensions

within the building structure.

Contrary to popular belief, walls covered with plants can also be drier. Rainfall is shed by leaves onto

the ground whilst the walls remain dry. This can also help to prevent the harmful effects of acid rain

since carbonic acid (formed by carbon dioxide and rainwater) is one of the substances responsible

for chemical weathering of stonework buildings (Jackson, 2001).

Because vegetation block and filter solar radiation, inhibit wind-flow, transpire water into the

atmosphere, reduce evaporation from soil, a controlled microclimate exists under a forest-like cover

of plants. They stabilise temperature, keeping it lower than the surrounding air during daytime and

preventing it from dropping greatly at night (Enis, 1984). The primary reason that vegetation has not

been applied more widely in energy-efficient buildings is a notable lack of experimental verification of

its effectiveness (Parker, 1987).



Building thermal performance can be significantly affected by the influence of vegetation on

microclimate. Influence on solar irradiance is probably the most significant with substantial influences

on air temperature, humidity, and airflow as well (McPherson et al., 1988, Brown and Gillespie, 1990).

Unfortunately, very few studies have measured detailed effects of vegetation on overall thermal

performance of buildings.

When the weather is cool, it is important not to shade the building surfaces that can benefit from solar

heating. In some cases, use of deciduous plants will allow summer shading and winter sun, in other

cases careful integration of native vegetation and building can give excellent results. Vegetation can

also be used to provide shelter from prevailing cold winds, thus reducing heat loss in buildings

caused by excessive draughts (Todd, 2000).

In many parts of the world, civic authorities are now aware of the psychological as well as physical

benefits which plants can bring. In Germany 1983, the Kassel City Co-operation launched a

campaign to encourage people to grow climbing plants (Witter, 1986). This was then spread to

Munich, Berlin and Frankfurt where guidelines for urban development include proposals for

vegetation on building fabric. Through the use of plants on walls, the urban climate and the

surrounding air quality can be greatly improved. This contribution lies greatly in the reduction of

extremes of temperature around buildings, facilitates of the circulation of air and as well as forming a

vegetative layer filtering all dust pollutants.

A more recent study, conducted at the Washington State University, was carried out to test the effect

of plants on people’s productivity. Results confirmed that where plants were added, the workers were

more productive, less stressed and 12% quicker reactions on computer tasks (Lohr).

2.1 Trees

Figure 3: The red rose plant adds decent colour to the building. Picture obtained from (Tredici, 1994) Old custom of having trees and plants around homes was

usually for enjoyment of nature’s aesthetic variety as seen in

Figure 3. The vegetation was also believed to be able to reduce

air-borne sounds with great efficiency if densely planted. The

viscous surface of leaves catches dust and filters the air. The

vegetation can also secure visual privacy and reduce annoying

glare effects from windows or building fabric. However, an

especially beneficial effect of plants is their thermal

performance. In winter, evergreen plants can block wind and

reduce heat loss from buildings and discourage drifting snow. In



summer, the surfaces of leaves absorb radiation, and their evaporation process can cool air

temperatures. Above all, they can provide generous shade at the right season. This makes

deciduous trees especially valuable when placed closed to buildings because the control of solar light

will not be interfered in the winter.

There are many ways to control excess solar radiation from reaching into buildings, especially when

the radiation acquires extra cooling energy. Of the many available systems, tree plantation can be a

delightful option in achieving much more than just energy saving. Trees help in reducing noise and

air pollution, modifying temperature and relative humidity and having great psychological effects on

humans.

Trees can modify both the microclimates around a building and the macroclimate of a region (Raeissi

and Taheri, 1999). Shade trees, windbreak trees, and snow fence plants are examples of plants used

for climate control. It is well known that plants alter adverse microclimates, making environment more

pleasant and liveable for man (Robinette, 1972). The significance of deciduous trees as passive

options is in the characteristics of growing leaves in the hot summer months when shading is most

needed and loosing them in the cool winter when shading is not desired.

When these trees are next to the position of windows, the resulting internal environment will be

greatly enhanced to a certain level of thermal comfort of the occupants. However, extensive

qualitative studies are necessary to ascertain the degree to which this occurs.

2.2 Vertical landscaping

Architecture, in particular the skyscraper, is a massive concentration of an inorganic mass onto a

small location. These inorganic construction materials totally imbalance the ecology of the site. To

counteract this, the building designer must introduce as much organic matter in the form of diverse

planting and landscaping. This is to compensate for and to match the imbalance. The intention is to

counter the intensive inorganic mass of the built structure.

In densely populated areas such as London, Hong Kong and Tokyo, designers need to find ways to

increase the total building floor area within limited land area. This also means that the increase of

street planting or landscaping within these densely populated areas could be an expensive trade-off

to building construction. However, if planting is introduced vertically along with building materials

such as facades, then more organic vegetation materials can be introduced into these inorganic

skyscrapers. This will balance off the extreme of having packed buildings in limited land without much

landscaping.



Figure 4: Singapore Exhibition Tower model and the vertical landscaping on the right. Picture

taken from (Davey, 1999)

There are a number of benefits in using vertical planting. These include:

• The ecology of the site will be enhanced by the increase use of vegetation within inorganic

building materials. The site’s biological diversity will also be raised with the increased amount

of plant material.

• The introduction of planting has aesthetic benefits for the users of the buildings and results in

improving morale and work productivity. Planting at the faces of building also enhances the

aesthetics of the skyscraper as a foliage structure.

• The planting, besides providing shading to the internal spaces and to the external walls, also

minimises heat reflection and glare into the building, thereby providing effective microclimatic

responses at the faces of the building.

• The evaporation process of the plants can also be an effective cooling device to the face of

the building.

• Plants absorb carbon dioxide and carbon monoxide (especially from external vehicular

emissions), and give out oxygen through photosynthesis, thereby creating a healthier and

cooler micro-environment within and around the façade of the building.

• Plants can act as visual screens and sound diffusers, especially at the sky courts, to reduce

the sound or noises from the external site.

• If the building is located in a draughty area, the vertical landscaping plants can also serve as

wind-breakers and reduce the strong wind flows.

2.3 Climbing plants

The use of vegetation on building fabric can play an important role in modifying the microclimate

around them (Meier, 1990b, Ong et al., 2000). The leaves of plants on walls provide a large surface,

which is capable of filtering out dust and other pollutants in the surrounding air. Large dense areas of



climbing plants on buildings can also reduce noise levels in the interior. Moreover, the layer of

climbing plants can also reduce annoying glare effects from windows or adjacent building fabric.

Climbing plants growing on buildings can also be used to provide shelter from prevailing cold winds,

thus reducing heat loss in buildings. When a layer of deciduous climbing plant is introduced next to

the building façade, incoming strong wind will reduce in speed and will also increase in humidity of

the air. This is due to the evaporation takes place on the leaf surfaces.

Low humidity levels in cities are common, and these green walls can provide some improvements.

Plants hold water on their leaf surfaces and through the processes of transpiration and evaporation;

they can add more water into the surrounding air (Yeang, 1992, Johnston and Newton, 1994).

Climbing plants are similar to trees in their beneficial effects to building’s thermal performance.

During the cold seasons, evergreen climbers can reduce heat loss from buildings by trapping stable

air within their thick foliage on the building fabric. This also applies to evergreen trees in which their

vast leafy branches hinder wind drifting onto the building and reduce convectional heat loss.

Climbing plants are mainly the type of vegetation which do not form a firm stem or trunk to support

themselves (Chesshire, 2001). Instead, they often scramble along and root themselves onto the way

until they find a suitable object that they can lean on. Once they have established the appropriate

object to climb on, climbers will grow rapidly upwards and sideways to receive the best location for

sunlight.

When applying climbing plants vertically on building fabric, it is necessary to take into consideration

about their specific climbing patterns. Different climbers have evolved their own methods for

attaching themselves to various surfaces. The following section lists the various ways that climbing

plants have adopted.

2.3.1 Climbing patterns

Apart from the characteristics of deciduous and evergreen, climbers can also be categorised

according to their climbing patterns.

A. Adhesive –sucker climbers

Figure 5: Young tendril with adhesive pads of Boston ivy. Picture taken from (Garden)

The branched tendril of Boston ivy, Parthenocissus

tricuspidata in Figure 5, is developing touch-sensitive

sticky pads that can allow them to cling on almost any

surfaces.



B. Root climbers

Figure 6: Hedera helix with clinging stem roots (FassadenGrün)

Root climbers can cling onto virtually any surface, except glass, and can extend

their roots into mortar if they find their way through cracks.

C. Twining climbers

This is the most common method of climbing plants. The twining climber will twist itself around

structures that it touches, and coiling clockwise or anti-clockwise depending on its particular kind of

species. Popular twining climbers are Morning glory and Wisteria.

Figure 7: Some vines have tendrils that wrap around any type of support. Picture taken from (Rothenberger, 2001)

D. Leaf-stem climbers

Young leaf stems from some climbers will grow out

from the main stem and start to twist around small

twigs and wires. Once they have established their

coiling around the support, the coil tightens and the

young leaf stem will develop into full-grown leaves.

Example of this kind of leaf-stem climber is

Clematis.

E. Leaf climbers

Figure 8: Vitis Coignetiae or grape vine (Gillian, 2000)

Leaf climbers are similar to leaf-stem climbers. The leaves of this type of

climbers act like tendrils structures and coil themselves onto the support. A

popular example of leaf climber is the grape vine as seen in Figure 7.

F. Scrambling plants

Figure 9: Many species of roses are armed with strong, pointing hooks on their stems. Picture taken from (Garden)

These types of climbers have hooked

thorns and enable them to protect from

predators and can also be hooked to hold

onto other plants. Climbing and rambler

roses are famous examples of these

hooked climbers.



2.3.2 Training systems for climbers

Having stated the various kinds of climbing methods that climbers may adopt, it is necessary to

provide the appropriate support they would need. The correct training system must be selected for

each specific climber. There are a lot of simple techniques available to act as the support framework

for climbers, such as netting, wire mesh or even a scaffolding of canes. These methods are easy to

setup and cheap for installation, but they are primarily for small scale or potted climbing plants.

Considering applying climbing plants with buildings in a larger scale, attractive training systems were

developed by companies who provide reliable and aesthetic training systems to building designers.

Figure 10 shows the various high-grade stainless steel systems for suitable climbers by the Jakob®

Inox Line Company.

Figure 10: Different training systems for climbers. Picture taken from Jakob Inox Green Solutions G1 catalogue

The dimensions of the training support system depend on the vigour, size and climbing pattern of the

chosen climber as well as the architectural structure of the building. The points that need to be

considered when choosing a training system are:

• The ideal height and width of the climber supports

• The distance of the training system away from the wall

• The wire rope spacing for vines

• The lattice sizes

• The wire rope or the rod diameters



Referring to Figure 10, type A and B climbers do not require a means of support. These are the

adhesive-sucker climber and the root climbers respectively as described in section 3.3.1. Their leaf

and stem modifications allow them to adhere to the nearby support and find establish their way

through building facades or other surfaces.

Type C in Figure 10 is the twining climber. Normally one single vertical support wire is required to

support this type of climber. If there is more than one twining climber, extra vertical ropes are

required. The distance between each vertical rope varies according to the growth rate of the climber.

As a rule of thumb recommended from specialist at Jakob®, slow growing climbers should have a

vertical spacing of about 200-400 mm. While very vigorous twining climbers should have vertical

ropes spacing of 400-800 mm.

Leaf-stem climbers and leaf climbers are Type D and Type E respectively in Figure 10. Grid-like or

rectangular structures provide the best supports for these climbers. The grid-like structures are

normally comprised of vertical ropes and horizontal rods. The lattice sizes are also different for slow-

growing and fast-growing climbers. For moderate growth rate climbers, a grid size of about 150 by

250 mm should be used. Those vigorous climbers should be provided with an approximate grid-size

300 by 500 mm of the support system.

Scrambling climbers are showed in Figure 10 as Type F. As these climbers possess hooks, they can

work their way up by using their epidermal outgrowths. Therefore horizontal rods should be provided

for this type of climbers. The spacing of rods is suggested by Jakob® specialists to be 250 mm for

slow growing scrambling climbers, and 500 mm spacing for fast-growing ones.

2.3.3 List of climbing plants

There is a vast range of climbers which can be applied vertically on and around buildings. The main

categories are deciduous, evergreen and herbaceous climbers. Table 1 summarised the types of

climbing plants which are most popularly grown with buildings, their main characteristics are also

summarised.



NameCommon

NameEvergreen/ Deciduous Hardy

Climbing method

Height (m)

Growth rate

Sun / Shade Soil type Pruning

Actinidia chinensis

Chinese gooseberry Deciduous

Frost hardy

Tw iner/ tw istng

9 or more Vigorous Full sun

Any reasonable No

Actinidia kolomikta DeciduousFully hardy Tw iner 3m to 7m Vigorous Full sun

Any reasonable No

Aristolochia macrophylla

Dutchman's Pipe

Deciduous/ perennial

Frost hardy Tw iner

5 or more

Vigorous, dense foilage

Sun/ Partial shade Fertile Winter

Campsis grandiflora

Trumpet Vine Deciduous

Not hardy

Self-clinging roots 6 to 9m

Vigorous (w hen establsihed)

Full sun/Sheltered spot Fertile Winter

Celastrus orbiculatus Bittersw eet Deciduous

Less hardy Tw iner

9 or more

Vigorous, dense cover

Sun/ Partial shade

Any reasonable Spring

Celastrus scandens Bittersw eet Deciduous

Less hardy Tw iner

6 or more

Less vigorous

Sun/ Partial shade

Any reasonable Spring

Clematis montanaVirgin's Bow er Deciduous

Frost hardy

Leaf-stalk tw iner

9 or more

Easy grow ing

Sun for the stems

Fertile/Moist (+chalk) Frequent

Hedera colchica Ivy EvergreenFully hardy

Self-clinging 10m Fast Shade/ Sun

Any garden soil Frequent

Hedera hibernica Irish ivy Evergreen HardySelf-clinging 4 x 4m Vigorous Shade/ Sun


Hedera helix Ivy EvergreenFully/ Half

Self-clinging 1.5m Fast Shade/ Sun


Humulus Lupulus 'Aureus' Golden Hop Herbaceous

Fully hardy Tw iner

6m or more Vigorous Full sun

Good, loamy, moisture Spring

Hydrangea petiolaris

Climbing Hydrangea Deciduous

Very hardy

Self-clinging 20 x 20

Vigorous (w hen establsihed) Shady w all Well-drained No

Jasminum off iciale

White Jasmine Deciduous

Frost hardy Tw iner 12m Fast

Sunny w arm site

Any reasonable No

Lonicera japonica 'Aureoreticulata' Honeysuckle Evergreen

Fully hardy Tw iner 10m Vigorous

Partial shade

Fertile/Moist (+shade)

After f low er

Parthenocissus tricuspidata Boston Ivy Deciduous

Fully hardy Tw iner 6 to 15

Tall and spreading Sun/ shade

Fertile/free-draining

Early spring

Parthenocissus quinquefolia

Virginia Creeper Deciduous

Fully hardy Tw iner 6 to 12m

Tall and spreading Sun/ shade

Fertile/free-draining

Early spring

Passif lora caerulea

Passion Flow er Deciduous

Frost hardy Tendrils 6m Moderate Full sun Free-draining April

Pileostegia viburnoides Evergreen Hardy

Self-clinging 5 m Moderate Sun/ shade

Fertile, moisture, acid

Spring for shape

Polygonum baldschuanicum Russian vine

Deciduous (Woody)

Fully hardy Tw iner

5 m each year Very tough

Sun/ Partial shade

Any reasonable

As required

Trachelospermum jasminoides Evergreen

Frost hardy Tw iner 6m

Dense foliage Full sun Well-drained

Early spring

Vitis coignetiae Vines Deciduous Hardy TendrilsUp to 20

mFast/ Vigorous

Sun/ Partial shade

Free-draining (+chalk) Summer

Wisteria sinensis Wisteria DeciduousFully hardy

Tw ining anti-clockw ise

Up to 30m

Rampant grow ing Full sun

Any reasonable Summer

Table 1: Popular types of climbing plants



3.0 Energy savings

Having introduced the different aspects on vegetation applications with buildings, there is one factor

that is very important to quantify, that is the related energy efficiency brought by plants. A plant wall

layer is actually like an additional layer of the external building fabric. When the sun is shining onto

the plant wall, the plant wall indeed receives the majority of the sun’s radiation and casting a shadow

on the wall itself. In this way, excessive rise in room temperature can be avoided and the cooling load

for the interior can be reduced. Furthermore, the leaves of the plant draw a lot of heat when they

transpire through the process of evaporation. Cool air is then drawn inwards and upwards, so warm

air is vented at the top of the façade, permitting more air circulation between the plant and the

building. This cools by means of the ‘chimney effect’.

Trees, shrubs and vines affect air-conditioning load mainly in five physical different ways. These are:

direct gain through windows, conduction through opaque surfaces, latent heat from infiltrating air,

sensible heat from infiltrating air, and shielding wind from air flows. The relative importance of these

depends greatly on the vegetation being used, the climate, the building shape and the building

orientation. Shading of direct solar gain is typically considered the factor most influenced by plants. In

some hot climates, the plant cover on walls can account to 25%-50% savings on peak cooling load

(Roseme, 1979).

Figure 11: Surface temperature difference of wall with and without shading. Graph taken from (Parker, 1983)

In a study of planting large trees and plants on the west side of a residential house, the results

showed that the west-wall temperatures were reduced by 28 degrees Fahrenheit (from 113°F to

85°F) during very hot, humid afternoon in South Florida (Parker, 1983). Figure 11 shows the result of

the experiment including a typical electrical utility load curve for a peak day load. Clearly, trees

precisely positioned to shade the west of the house, combined with the effect of the planted hedges,

can dramatically reduce electrical consumption by air-conditioners during the peak period.



Another study conducted by Parker (1987) on the comparisons of energy consumption profile of a

residential building in the United States before and after introducing plants and trees placed adjacent

to the building, results indicated energy savings of up to 60% during warm summer days. Also, peak

power demands due to air-conditioning the building are reduced by about five kilowatts (Parker,

1987, Meier, 1990a). The result confirms that vegetation is a very effective passive solar cooling

technique.

In the daytime on clear days in Japan, the direct solar radiation received from the surroundings at the

ground was 291 W/m², while that under the wisteria sunscreen was about 70 W/m², approximately

one quarter of the former. A difference of the mean radiation temperature under a plant pergola and

at the open ground was found to be 6-8°C in the daytime (Hoyano, 1988).

The ‘cool’ feeling people experience under plant screen is a result of a reduction in radiation

received. Many researchers have investigated the porosity, or transmissivity values of tree canopies,

in both summer and winter. This information had seldom been translated, though, into estimates of

the amount of radiation a person would receive under a given tree specimen or the thermal comfort

amenity of the trees (Brown and Gillespie, 1990).

Windbreak plantings in rural areas might reduce wind-induced air infiltration by up to 50%, and heat

loss by conduction or convection through windows by up to about 9% (Ticknor, 1981). This shows

that climbing plants on building external walls can, to a certain extent, affect the internal thermal

comfort of occupants.

Plant leaves can be 1°C lower than the ambient temperature and damp surfaces like grass, soil can

be even 2°C or more below and can contribute significantly to a cooler building. Façade planting can

therefore lower ambient temperatures in summer time and heat gains can be reduced by as much as

25% (Kurn et al., 1994).

Plants evaporate water through the metabolic process of evapo-transpiration. The water cycle is

carried from the soil through the plant and evaporated from the leaves as a part of the photosynthesis

process. A single properly watered tree can evapo-transpirate about 40 gallons of water in a day

(equivalent to 230000K calories of energy in evaporation). This fact can be seen as offsetting the

heat equivalent to that produced by one hundred 100-Watt lamps, burning eight hours per day

(Rosenfield, 1997).

The transpiration of water by plants will help to control and regulate humidity and temperature as well.

As stated above, a single large tree can transpire about 40 gallons of water in a day. The mechanical

equivalent is 5 average room air-conditioners, each at 2500K calories per hour, running 19 hours a



day. Air-conditioners only shift heat from indoors to outdoors and also use electric power. The heat

therefore still exists to increase urban air temperatures, contributing to even higher inside

temperature. Thus increasing the loads of air-conditioning plants. But with the use of plants and other

trees, transpiration renders the heat through the vegetation itself as well as providing shade to the

building. Therefore, savings in cooling load by plants can be extremely significant.

The use of vegetation to improve the building’s microclimate has long been investigated by a number

of researchers around the world. Although their methods varied, nearly all the results confirmed that

using vegetation around buildings could provide a better comfort for the occupants. Table 2 is a

summary of the findings.

Author and year Location Type of planting

Wall-vegetation distance

Parameters measured Results

(Hoyano, 1988)

Fukuoka City, Japan

Horizontal wisteria sunscreen N/A

Top and bottom surface temperatures of sunscreen

2ºC higher on the top of sunscreen

(Hoyano, 1988)

Kyushu University, Japan

Vine sunscreen (35º inclined angle to the sun) on veranda

N/A Veranda with and without vine sunscreen

Veranda without vine screen was 1-3ºC higher

(Hoyano, 1988)

Tokyo, Japan

Ivy attaching and covering west-facing wall

Touching Wall with and without ivy

18ºC lower with ivy covered

(Di and Wang,1999)

China Ivy-covered wall at Tsinghua University

Touching Ivy and wall temperatures. Wall with and without ivy.

Leaf temp was 8.2ºC higher than wall beneath. Leaf temp was 4.5ºC lower than that of the bare wall

(Cantuaria, 2000) London Virginia Creeper

covered on wall Touching Wall with and without creeper

Vegetated wall 10ºC lower than unvegetated

(Ong et al., 2000) Singapore South parapet with

potted plants N/A Parapet with and

without potted plants Parapet with potted plants was 4ºC lower

(Papadakis et al., 2001)

Athens, Greece Deciduous trees Not

mentioned Wall with and without tree shading

Unshaded wall up to 600W/m2 solar radiation, but 100W/m2 on shaded wall

(Evans et al., 2000)

Brighton, United Kingdom

Inclined framework of deciduous plants on roof

N/A Global irradiance on roof surface with and without plants

Energy received at roof surface was reduced by 39%

(Evans, 2002) Brighton, United Kingdom

Inclined framework of deciduous plants on roof

N/A

Direct and diffuse radiation on roof surface with and without plants

Energy summer cooling load reduced by 15%

Table 2: Summary of experiments and results of relevant researches (Lam et al., 2003)



4.0 Plant application examples

A lot of buildings employing vegetation in their designs are sometimes classified as bioclimatic

buildings. Bioclimatic describes an approach to building design which inspired by nature and which

applies a sustained logic to every aspect of a project, focused on optimising and using the

environment (Lloyd, 1998). It is a way of designing the buildings to conserve energy use and exploit

natural resources such as sunlight and daylight in the best effect without much use of mechanical

systems within the building.

Bioclimatic buildings bring in a number of factors such as:

• Carefully balance the solar heat gains when the weather is hot, whilst fully utilising solar

radiation when the weather is cold.

• Sunlight and daylight should be abundant to enter into the building but guard against glare,

excessive solar gains and excessive heat loss.

• Amount of fresh and clean air quality should be achieved inside the building.

• The building fabric should be able to absorb and release heat on a daily cycle, whilst

sufficiently insulate the building in cold weathers.

Most of the above factors can be achieved by introducing plant growth on building fabric. Firstly, plant

growth on walls can block excessive solar gains, while the use of deciduous plants can help to allow

sunlight to shine directly onto the building walls in winter to provide warmth. Secondly, plants can

produce oxygen and fix carbon dioxide in the air and so improve the quality of air in the surroundings.

Finally but not least, the transpiration of plants absorbs heat from the vicinity of the site to provide a

cooler environment.

Examples of bioclimatic buildings are becoming popular nowadays. One of the most sophisticated

prototypes of bioclimatic skyscraper is the Singapore Exhibition Tower as seen in Figure 4. It is

designed by the famous architect Ken Yeang from T.R.Hamzah & Yeang. This architect is very keen

in developing bioclimatic buildings, especially associated with tall eco-friendly projects. The amount

of vegetation used in his designs is extensive. According to the architects, these plants provide

shade and improving interior microclimate and oxygenation. Although plants are used as climate

modifiers, some air-conditioning is still required in tropical climate as in Singapore. However, the

need for air-conditioning is reduced.

There are numerous types of bioclimatic buildings throughout the world, and most conventional

building designs also incorporated the use of plants. It is evident that the use of plants is a significant

feature in the designing of buildings. Below are some recent examples.



The J-R office building

The J-R building is located on the 10th Parallel in Costa Rica, a tropical country in Central America.

The building is designed by Bruno Stagno, a Chilean-born architect who practices in San Jose. The

J-R building is surrounded by a steel mesh. Climbing plants were introduced to grown onto the

framework, and it took six to eight months for the plants to cover the facades. This is shown in Figure

12.

Shading is required at all seasons in tropical Costa Rica, so evergreen plants Thumbergia and

Bignoniaceae are used. The "green screen" wrapping the J-R office building creates a shaded

microclimate on the north and south facades, reducing direct sun on the glass without darkening the

interior. The east and west faces are closed (Stagno, 2002). The architect, Stagno Bruno, did not

perform any thermal modelling for this vegetative design, but he confirmed that plants can reduce the

ambient air temperature by at least 3°C in tropical climate. The architect also designed another

similar vegetated building - Credomatic Building, in which the model is shown in Figure 13.

Figu ing re 12: The J-Y office building with and with climbing plants. The green framework wrappthe J-R building creates a shaded façade. Pictures provided by Bruno Stagno

Figure 13: Credomatic Call Centre designed by Bruno Stagno. Picture provided by Bruno Stagno



The Consorcio-Santiago Building (1990 - 1993)

This building is situated in Santiago, Chile and is designed by the architects Enrique Browne and

Borja Huidobro. The west side of the building is the intolerable side for solar radiation. Therefore the

architect designed stepped greenery to cover this façade as seen in Figure 14. By encouraging the

plants to grow on and up the walls of large commercial buildings, the natural environment will then be

extended into the urban areas and as well as providing a comfortable environment for all working

staff.

Figure 14: Light filters through the green wall into the office interior if the Consorcio-Santiago Building. Photographer: Guy Wenborne. Pictures provided by Enrique Browne

The types of plants used are Rosa Banksiae Normalis, Plumbago Capensis, Bouganvillea Glabra

and Ampelopsis Quinquefolia. These are all deciduous plants because the designer wants to protect

the west side of the building from the sun in summer, whilst allow solar to enter the building during

winter. Another advantage is that the vegetative skin changes its colour during the seasons.

This commercial building is air-conditioned, and is having a more economical use when the

vegetation was fully grown. There is no empirical survey done on the actual performance of the

vegetation skin. However, the architect estimates that the "vertical greenery" reduced 60% of the sun

absorption, thereby reducing about 10% the total energy cost of the building.

Consorcio-Concepcion Building (2003-2004) The Concepcion building is located south of Santiago, designed by architect Enrique Browne. The

building composes the double green skin with mature climbing plants on the East, North and West

sides. The various types of climbing plants used are shown in Figure 15.



Figure 15: Consorcio-Concepcion Building. Photographer: Guy Wenborne. Pictures provided by Enrique Browne,

The MFO Park

The MFO Park is located at the industrial area of Zurich. It is an open hall that is 100 metres long, 35

metres wide and 17 metres high. This park was mainly constructed using innovative steel cables

which are wrapped by different magnificently growing climbers. A total number of 1300 climbers in

different varieties will flourish the metal structure. In course of time, the entire park will form green

and blossoming walls, ceilings for pergolas, covered walkways and garden spaces.

Figure 16: The MFO Park in Zurich. Pictures provided Virginia Creeper



5.0 Bioshader Experiment

‘Bioshader’ is the term used to describe the new biological shading devices for building designs. This

sustainable shading design option comprises a vertical layer of deciduous climbing plant canopy that

trails on a metal framework, which is mounted external to the glazed facade of a naturally ventilated

building. This setup is shown in Figure 17.

Solar heat absorbed by metal-shading devices can be re-radiated into building and it heats up the air

before entering the building. Whereas a layer of deciduous climbing plants external to the windows

can reduce the solar gain and regulate the temperature of air on the shaded side. Apart from

modifying the solar gain, the bioshader can also improve the air quality, increase the moisture

content and also attenuate the external noise.

Plant container

External stainless steel framework

In the summer, the dense foliage of the bioshader blocks the high angle sun

Openable window

Bioshader – deciduous climbing plants grown on a robust framework

In the winter, the bioshader sheds off its leaves; this allows low angle solar radiation entering the building

Figure 17: A vertical section through the bioshader system (Ip et al., 2004)

The bioshader’s shading effect changes with its growing and wilting seasons from spring to winter. In

the winter, deciduous plants have bare branches that allow low angle solar radiation through the

glazed facade into the building interior. Whereas in the summer, the dense leaf foliage absorbs solar

radiation and, through the evapo-transpiration process, lowers the air temperatures.

An experiment was set up at the School of the Environment, University of Brighton, to evaluate the

bioshader’s thermal shading performance. The aim of the experiment is to measure and evaluate the

bioshader’s shading effect to an occupied office. The results were compared with an identical office,

acting as the control room, which has no bioshader.



The following sections outline the physical setup of the experiment, the selection of deciduous

climbing plant, the equipment and experimental layout, the test and control rooms details, the

measurement and data collection procedure.

5.1 Plant selection for bioshader experiment

The integration of vertical greenery onto contemporary architecture presents a novel design

opportunity for designers and architects. When incorporating a framework of deciduous climbing

plants external to buildings, the selection of a suitable plant is very important and has to take into

consideration factors such as climate, growth rate, leaf coverage and maintenance. This section

summarises the selection criteria for bioshader and also the justification for the climber to use in the

experiment.

5.1.1 Plant Selection Criteria

Table 2 shows a summary of the plant selection criteria that were identified and considered. These

criteria were used for the selection of climber in the bioshader experiment.

Factor Possible criteria Selection criteria Details

Growth rate Slow, moderately fast, vigorous Vigorous or fast Limitation of research time for plant

growth

Leaf size Large, small Large Larger leaf creates large shading effect

Height climber can reach High level, low level Higher level The higher the climber can reach, the

greater coverage

Winter temperature tolerance

Fully hardy (withstand temp down to -15°C), frost hardy (withstand temp down to -5°C), half hardy (withstand temp down to 0°C) (Brickell, 1999)

Fully hardy Fully hardy plant can sustain through cold winter times

Maintenance High, Low Low

The frequencies of watering, pruning and adding fertilizers increase the overall cost. Lowering these costs attracts designers and clients to adopt this kind of design

Orientation/ Sun preference Full sun, partial shade, shade Full sun Full sun to act as shading device.

Weather tolerance Costal, sheltered, windy etc. High tolerance Climber able to withstand adverse

weather conditions

Types of soil Sandy, coarsely, acidity, alkalinity etc.

Moist, humus-rich, loose-packed

Maintaining nutrients in the soil for climber to absorb will enable prosperous growth

Climbing patterns Adhesive, twining, clinging Twining or clingingClimbing framework for the climber to grow on. So adhesive type is not suitable

Table 3: Selection criteria of climbing plants for use as bioshaders (Lam et al., 2002)



5.1.2 Plants suitable for the United Kingdom climate

The growth of plants relies mainly on water, sunlight, oxygen, climate and the other necessary

minerals. Being one of the major factors, the local climate at which the plant is growing is a very

important decisive factor when selecting the appropriate plant. The experimental measurement was

being carried out at the University of Brighton which is situated in the southern part of the United

Kingdom. The average temperature in this location is a few degrees warmer than most parts of the

United Kingdom, with earlier springs, warmer summers and milder winters. The lowest winter

temperature is rarely below –5ºC. There are constant onshore breezes with occasional strong winds.

Taking the locality regional weather conditions and the criteria identified in Table 3, a number of

possible climbing plants were selected from Table 1. These are shown in Table 4 in order of their

suitability to this experiment.

Species Common Name Hardy Climbing

method Height (m)

Growth rate Leaf / Flower Soil type Pruning

Parthenocissus quinquefolia

Virginia Creeper

Fully hardy Twining 6 to 12

Fast, tall and spreading

Very large 5-oval leaflets

Fertile/free-draining Early spring

Polygonum baldschuanicum

Russian vine

Fully hardy Twining 5 m/ year Very tough Small leaves Any

reasonable Frequent

Parthenocissus tricuspidata Boston Ivy Fully

hardy Twining 6 to 15 Fast, tall and spreading

3-lobed leaves Fertile/free-draining Early spring

Wisteria sinensis Wisteria Fully hardy Twining Up to 30m Rampant Hanging blue

flowers Any reasonable Summer

Vitis coignetiae Vines Half hardy Tendrils Up to 20m Fast Very large

leaves Free-draining, alkaline soil Summer

Table 4: Summary of climbers in their order of their suitability for use as bioshader in the southern part of the United Kingdom. Based on plant characteristics described in (Brickell,

1999, Chesshire, 2001)

The most appropriate climbing plant to be used in this research is Virginia Creeper. The unique ‘large

5-oval leaflets’ character makes it a good bio-shading device. Also it is tall, fast spreading, and

requires pruning only in early spring. This is relatively more advantageous than Russian vine which

requires frequent pruning due to its excessive rampant growth. The leaves of Wisteria are small and

so shading efficiency is lower than Virginia Creeper. Whereas, Vitis Coignetiae is only half-hardy

which may not withstand the winter cold. On balance, Virginia Creeper is the best option.

5.2 Experimental setup



5.2.1 The Site

The proposed bioshader system is suitable for low-rise lightweight office buildings. The construction

type of the building will not constitute a great issue on its suitability on applying this bioshading

system. This is because the system uses trailed climbing plant on a framework and therefore, the

main issue is whether there is the possibility of having a framework for the bioshader to grow on

outside the building. Almost all types of buildings can be fitted with an external metal framework.

The selected building is naturally ventilated with large windows to allow the bioshader to locate

externally on the metal framework. The offices or buildings that the bioshader can incorporate are

best to be suffering from summer excessive solar heating. And the reduction of solar could increase

the comfort to the occupants. Within the UK, these buildings should be due to face south or south-

west. This is because these are the orientations that are most solar tolerant.

F p
igure 18: Maps showing the location where the bioshader experiment was setu


The bioshader experiment was set up in the Cockcroft Building at the Moulsecoomb site of the

University of Brighton. Figure 18 shows the location of the experiment. Two identical offices on the

first floor were selected as the test and control rooms. Each room measures 3m by 3m by 3m. There

are two windows in each room; each window measures 1.2 m by 2.1 m. The windows are facing

south-west and both rooms are situated next to each other. The rooms are subjected to excessive

summer solar gains. Both rooms are occupied by one member of staff at normal office hours.

5.2.2 Plant and External Framework

The external stainless steel metal framework, covering the two windows in the test room was

supplied by Jakob®-UK (Mendip Manufacturing Agency) which is an international company

specialising in architectural plant support frameworks (Jakob 2003). The entire framework, as shown

in Figure 19, comprises of 4mm vertical stainless steel wires and horizontal rods. These were fixed

together with specialised cross clamps making up the spacing of 150mm x 200mm lattices. Spacer

baskets of 150mm long were used as fixings to the building façade.

Angle bar

Cross clamp

Rod

4mm rope

Spacer basket

Figure 19: The details of the stainless steel framework

A total number of four plant containers were used. They were evenly lined below the metal

framework under the two windows in the test room as shown in Figure 20. The internal dimension of

each plant container is 400mm (length) by 300mm (width) by 600mm (height) and they were tailored

made from lined plywood. A layer of 2.5mm aggregates was put at the top of the drainage holes at

the bottom of the containers to prevent the compost from clogging up and blocking the drainage

holes.


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Bioshaders on metal framework outside the test room windows The windows of

the control room using internal blinds for solar shading

Virginia Creeper

Plant container

Figure 20: The Virginia Creeper trained onto the framework and the plant containers

Four Virginia Creeper plants were planted in the containers were trailed onto the framework. The

compost used was mixed with a type of water-storage gels which can hold up water and release it if

the soil is dry. A six-month slow release fertiliser was also mixed into the compost to provide the

necessary nutrients for the plants.

5.2.3 Measuring Equipment

The locations and types of sensors used in the bioshader experiment are shown in Figure 21.

Control Room

Internal temp and RH

Test RoomCentral data logging unit Air

flow

Solar flux energy sensor

External temp and RH

Dome solarimeter

N

Air flow

Solar flux energy sensors

Internal temp and RH

Corridor temp and RH

Gap temp and RH

Figure 21: Plan showing locations of monitoring equipment


Two extractor fans were installed to provide controlled mechanical ventilation inside the two offices.

The air velocity, air temperature and relative humidity are monitored with sensors installed in the air

ducts. The location of the external dome solarimeter, solar flux energy sensors, external relative

humidity and air temperature sensors are also shown in Figure 22. The external dome solarimeter

was fixed vertically onto the wooden plant container. The indoor solar flux sensors were secured by

means of moveable clamps so that the flux sensors can be positioned anywhere across the windows.

Figure 22: Cross section of the bioshader with the locations of sensors

The test and control rooms were fitted with door sensors for the detection of room occupancy. As the

thermal environments of the rooms would be affected when doors were opened, data of the days with

occupancy were excluded in the analysis.

All sensors were linked to the central data logger through the junction boxes. The Agilent 374370A

data logger base unit was selected as the central logging system, it has two 20-channel differential

multiplexer cards which allows up to 40 channels of data logs. All measuring and monitoring

equipment in the control and test rooms were connected to this central logging system in the

adjacent room.



Apart from data recorded from the data logger, photos were taken every other day to monitor the

growth rate of the plants. These regular photographic shots were taken during the summer season of

year 2003. The solar transmittances by various leaf layers were monitored on sunny days throughout

the summer.

The well established Virginia Creeper were planted from their pots into the troughs on the 13th May

2003 and the monitoring equipment were completely installed in June 2003, The data logging started

from the 25th June 2003, and the experiment ended on the 31st August 2004. A total number of 14

months’ data, recorded at every two-minute interval throughout the experimental period, were

collected.

The plants were pruned twice over the experimental period. The first time was on 4th Aug 2003 and

the second pruning was on the 24th May 2004 to provide a good growth start for the new summer

season.



6.0 Results

The collected data were organised and analysed. Three main areas were examined: the temperature

changes by the bioshader, the relative humidity changes and the solar transmittances by Virginia

Creeper. This section will summarize the findings from the bioshader experiment.

6.1 Data Selection

The collection of the data had been running for 14 months. There had been interruptions during this

period of time, so any noise data will be omitted from the dataset. The test and control rooms are

occupied offices with staffs going into and out of the rooms. This would affect readings on the thermal

environment of the rooms. Therefore, the occupancy sensors were used as an indication for data

selection as well. Mostly, weekend data were used for analysis when no one occupied the rooms.

The selected dates were Sundays, with different types of weather conditions such as sunny and hot,

windy and gloomy. This would provide a broader view of the bioshader performance on different

environmental conditions.

6.2 Temperature Comparison

Temperature inside the test room was modified significantly by the bioshader, and can be

represented by selected Sundays between July and October when the rooms were not occupied.

Figure 23 to Figure 30 show the temperatures in the test room, the control room, the plant canopy

and the external ambient air.

Temperature distibutions on 13th July 2003

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pera

ture

(deg

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Test rmTemp °C

Control rmTemp °C

CanopyTemp °C

Ambient AirTemp °C

Temperature distributions on 20th July 2003

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Test rmTemp °C

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CanopyTemp °C

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Figure 23: Temperature distributions on 13th July 2003

Figure 24: Temperature distributions on 20th July 2003



Temperature distributions on 10th Aug 2003

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Temperature distributions on 24th Aug 2003

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Figure 25: Temperature distributions on 10th Aug 2003

Figure 26: Temperature distributions on 24th Aug 2003

Figure 27: Temperature distributions on 21st Sept 2003

Figure 28: Temperature distributions on 28th Sept 2003

Figure 29: Temperature distributions on 12th Oct 2003

Figure 30: Temperature distributions on 26th Oct 2003

Temperature distributions on 21st Sept 2003

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1

10:1

7

11:1

3

12:0

9

13:0

5

14:0

1

14:5

7

15:5

3

16:4

9

17:4

5

18:4

1

19:3

7

20:3

3

21:2

9

22:2

5

23:2

1

Time

Tem

pera

ture

(deg

C)

Test rmTemp °C

Control rmTemp °C

CanopyTemp °C

Ambient AirTemp °C

Temperature distributions on 28th Sept 2003

8.0

10.0

12.0

14.0

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18.0

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26.0

28.0

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103

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04:0

105

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06:0

107

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08:0

109

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10:0

111

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12:0

113

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14:0

1

15:0

116

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17:0

118

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120

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21:0

122

:01

23:0

1

Time

Tem

pera

ture

(deg

C)

Test rm Temp°C

Control rmTemp °C

CanopyTemp °C

Ambient AirTemp °C

Temperature distributions on 26th Oct 2003

0.0

5.0

10.0

15.0

20.0

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0

00:5

8

01:5

6

01:5

4

02:5

203

:50

04:4

8

05:4

6

06:4

407

:42

08:4

0

09:3

8

10:3

6

11:3

4

12:3

213

:30

14:2

8

15:2

6

16:2

417

:22

18:2

019

:18

20:1

6

21:1

422

:12

23:1

0

Time

Tem

pera

ture

(deg

C)

Test rmTemp °C

Control rmTemp °C

CanopyTemp °C

Ambient AirTemp °C

Temperature distributions on 12th Oct 2003

0.0

5.0

10.0

15.0

20.0

25.0

30.0

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1

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102

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03:0

104

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05:0

106

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07:0

108

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09:0

110

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112

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13:0

114

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116

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118

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120

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21:0

122

:01

23:0

1

Time

Tem

pera

ture

(deg

C)

Test rm Temp°C

Control rmTemp °C

CanopyTemp °C

Ambient AirTemp °C

6.3 Relative Humidity Comparison

The bioshader located outside the test room also affected the internal room relative humidity. Figures

31 to 38 show the comparison of the relative humidities inside the test room and the control room on

selected Sundays from July to October.



Relative humdiity distributions on 27th July 2003

3035404550556065707580

00:0

1

02:0

1

04:0

1

06:0

1

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1

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RH

%

Test rmRH %

Controlrm RH %

Relative humidity distributions on 13th July 2003

20

25

30

35

40

45

5000

:00

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0

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Time

RH

%

Test rmRH %

Controlrm RH%

Figure 31: Relative humidity 13th July 2003

Figure 32: Relative humidity 27th July 2003

Figure 33: Relative humidity 10th Aug 2003

Figure 34: Relative humidity 24th Aug 2003

Figure 35: Relative humidity 21st Sept 2003

Figure 36: Relative humidity 28th Sept 2003

Relative humidity distributions on 24th Aug 2003

20

30

40

50

60

70

80

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1

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1

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RH

%Test rmRH %

Controlrm RH %

Relative humidity distributions on 10th Aug 2003

20

25

30

35

40

45

50

55

00:01 02:01 04:01 06:01 08:01 10:01 12:01 14:01 16:01 18:01 20:01 22:01 Time

RH

%

Testrm RH%

Controlrm RH%

Relative humidity on 21st Sept 2003

30

40

50

60

70

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Time

RH

%

Test rmRH %

Controlrm RH %

Relative humidity on 28th Sept 2003

20

25

30

35

40

45

50

55

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1

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1

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1

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1

Time

RH

%

Test rmRH %

Controlrm RH %

Relative humidity on 12th Oct2003

20

25

30

35

40

45

50

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1

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1

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Time

RH

%

Test rmRH %

Control rmRH %

Relative humidity on 26th Oct2003

20

25

30

35

40

45

50

55

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0

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0

23:0

0

Time

RH

%

Test rmRH %

Controlrm RH%

Figure 37: Relative humidity distributions on 12th Oct2003

Figure 38: Relative humidity distributions on 26th Oct2003



6.4 Leaf Solar Transmittance

Leaf solar transmittance is the fraction of solar ra

Leaf covering the solar flux sensor

Solar flux sensor

diati

The solar transmittance of the bioshader would depe a

Creeper plants. The foliage is the thickness of the t

number of leaf layers would have different value

solar transmittance will decrease with increasing nu

s of experime rried out to find the solar transmittance ngle or multi

layers of Virginia Creeper leaves. The solar flux energy sensors were moved across locations of the

whe r or five layers of leaf accordingly (as seen in figure 39).

Figure 39: On le-leaf

Since all the sola r radiation data

logge nt to take into

account of their ve of the external solar

radiations were g known latitude,

decli alculations can be

found in Appendix A.

culated using the following equation:

on which is directly transmitted through the leaf.

ndent on the foliage and coverage of the Virgini

plant, which is the number of leaf layers. Differen

of solar transmittances. Generally speaking, the

mber of leaf layers.

nts were caA serie s through si

plant re there were one, two, three, fou

Repeated measurements were taken on the external solar radiation on the surface of the leaf or

leaves, and the transmitted radiation behind the leaf or layers of leaf.

e layer of leaf covering the solar flux sensor for the determination of singsolar transmittance

r sensors in this experiment were fixed vertically, the total sola

d by the external dome solarimeter and the solar flux sensors required adjustme

rtical positions. The vertical and horizontal components

derived from generic equations by (Sukhatme, 1996) usin

nation, slope of the bioshader, wall azimuth and hour angle. Details of the c

Having corrected all the measured solar radiation data, the leaf solar transmittances are then

cal

II

TExtn

n = (Equation 1: Leaf solar transmittance)



Where:

Tn = Solar transmittance with nth layers of leaf

t = External incident solar radiation perpendicular to the leaf canopy [W/m2]

he calculated results are shown in Appendix B. Results which are considered as outliners were

excluded in the calculation for the mean values of solar transmittances were obtained. Table 5

summarise

layer 1-leaf 2-leaves 3-leaves 4-leaves 5-leaves

IEx

In = Solar radiation measured by the solar flux sensor behind nth layers of leaf [W/m2]

T

s the calculated mean solar transmittances for one to five layers of Virginia Creeper leaf.

Leaf

M n solar transmittance 0.43 0.34 0.25 0.21 ea 0.14

Table 5: The mean solar transmittances of one to five layers of Virginia Creeper leaf



7.0 Discussion and Analysis

The thermal performance of the bioshader was evaluated by comparing the temperatures, relative

humidities and solar gains of the test and control rooms. The following sections analyse the findings

of the bioshader experiment showed in the previous chapter.

7.1 Temperatures and Relative Humidities

Figure 23 to Figure 30 are the summaries of temperatures of the ambient air, the test room, the

control room and, the gap between the leaf canopy and the window. As both the test room and

control room are facing South-west, there were high solar gains in the afternoon. The high room

temperatures inside both of the rooms were due to the low volume flow of air through the ventilation

fans. On the whole the temperatures in the test room were consistently lower than that of the control

room, with peak temperature differences shown in Table 6.

Table 6: Peak difference temperatures (°C) between test and control rooms on selected Sundays

Date 13 Jul

03

20 Jul

03

10 Aug

03

24 Aug

03

21 Sep

03

28 Sep

03

12 Oct

03

26 Oct

03

Time 15:45 16:00 15:30 17:00 15:15 14:40 14:20 13:30

Peak temperature

difference between

Test room and

Control room (°C)

4.1 5.6 3.9 4.4 4.3 5.3 3.8 1.1

The peak temperature differences over the eight selected Sundays range from 1.1°C in October to

5.6 °C in July. As the control room and test room are identical in terms of size, construction and

orientation, theoretically they should have the same internal thermal environments. However, graphs

in figures 23 to 30 and peak temperatures differences in Table 6 suggest that the additional layer of

bioshader to the test room is the main effect to the substantial reduction in room temperature.

July, August and September are the three hottest month in the UK. In July, the external air

temperature was well above 24°C in figure 23 and was maintained at around 20°C on figure 24.

Irrespective to the different external ambient air temperatures on both days, the bioshader had

lowered the test room temperature by at least 4°C at the hottest time in the afternoon. According to

CIBSE, the recommended summer comfort temperature for offices should be in between 22-24°C

(CIBSE, 2004). In figure 24, the bioshader had reduced the test room temperature to the



recommended level of the comfort temperature range recommended by CIBSE, while the control

room temperature reached a peak temperature of 30°C at the same time. This is shown in Figure 40.

20.0

21.0

22.0

23.0

24.0

25.0

26.0

27.0

28.0

29.0

30.000

:00

01:1

0

02:2

003

:30

04:4

005

:50

07:0

0

08:1

009

:20

10:3

011

:40

12:5

0

14:0

015

:10

16:2

017

:30

18:4

0

19:5

021

:00

22:1

023

:20

Test rm Temp °CControl rm Temp °C

comfort range

Figure 40: Bioshader reduced room temperature to comfort range

Looking at a wider period on how the bioshader can reduce the substantial heat gain into the test

room, Figure 41 shows the comparison of temperatures of the test room, the control room and the

exterior over the August month. The red curve, control room temperature, is constantly higher than

the blue curve, which is the test room temperature. There are also peaks on the control room

temperature curve which represent each of the hot afternoons over August. All these peaks are

lowered on the test room temperature curve, showing that each day the heat gain into the test room

was reduced by the additional layer of bioshader. The main reason of the decrease in test room

temperature is the direct solar shading by the bioshader, which prevents heat being stored in the low

ventilated room and in turn prevent rising the room temperature.

Evapo-transpiration from the climbers is also another contribution to the reduction in test room

temperature. Heat energy is required in the evaporation of water from plants. The heat added during

evaporation is acquired from the climbers’ surroundings and thus removing excess heat from the

microclimate.



10.0

15.0

20.0

25.0

30.0

35.0

40.0

31/07/2003 00:00 05/08/2003 00:00 10/08/2003 00:00 15/08/2003 00:00 20/08/2003 00:00 25/08/2003 00:00 30/08/2003 00:00

Test Temp °C

Control Temp°C

External AirTemp °C

Figure 41: Temperature profiles of test room, control room in August

The results showed in Figures 23 to 30 also demonstrated the ‘blanket’ effect of the leaf canopy.

Over the eight Sundays, the temperatures between the plant canopy and the window were higher

than the external air temperature. The canopy temperature was particularly high after midday and

remained so until the early morning. This can be attributed to the relatively higher surface

temperature of window glass as it was heated up by the solar gain during the day, which was later

maintained by the heat released from the room at night.

The other important bioshader improvement to the test room thermal environment is on the relative

humidity level. Figures 31 to 38 in the results section show the comparisons of relative humidities of

the test room and the control room. The test room has consistently higher relative humidity than the

control room on all of the selected Sundays. This was mainly due to the relatively lower air

temperature in the test room. The presence of the bioshader also adds moisture into the air from the

climbers, in which the moisture might have brought into the test room and improve the internal

humidity level.

The relative humidity level in the test room was considerably higher than that of the control room with

peak difference ranging from 4.9% in October to 13.7% in September. The peak differences for each

selected Sunday were shown in Table 7.



Date 13-Jul-03

27-Jul-03

10-Aug-03

24-Aug-03

21-Sep-03

28-Sep-03

12-Oct-03

26-Oct-03

Time 15:46 15:25 15:29 16:35 15:11 14:43 14:21 13:20

Peak relative humidity

difference between Test

room and Control room

10.2% 13.5% 8.4% 11.7% 13.7% 11.8% 9.0% 4.9%

Table 7: Peak differences in relative humidity between test and control rooms

According to CIBSE, under normal circumstances the humidity level should be in the range of 40-

70% (CIBSE, 1999). Some of the selected Sunday results are below 40% relative humidity level in

the control room. Although the relative humidity level in the test room was higher by an average of 8

to 10%, this difference could make a big effect on the occupants’ comfort. When relative humidity is

as low as around 30%, occupants can experience dry eyes and may also result in other sick building

symptoms.

In October, both rooms’ temperature and relative humidity differences dropped when compared to

previous months over the summer. This is directly related to the growth of the bioshader. The

climbers started to grow vigorously in June, and the foliage of the plants reached maximum in July.

Pruning was performed at the beginning of August which had greatly reduced the thickness and

shading effect of the bioshader. This explains the reason why in August both the temperature and

relative humidity peak differences were declined as the bioshader was pruned and cannot perform its

full ability to improve the test room environment.

After the August pruning, the temperature and relative humidity peak differences (as shown in Table

6 and 7) increase steadily until the end of September. This corresponds to the steady growth of the

bioshader over August and September and thus having increasing affect onto the test room

environment. Referring to the photographic evidence taken over the summer to monitor the plant

growth, the bioshader reached its full foliage in September after the pruning, and was maintained

until mid of October. This was when the weather changed from summer to autumn and the leaves

started to shed, and performance of the bioshader decreased. This explains the decrease in peak

differences in Table 6 and 7.

7.2 Effect of solar reduction by leaves

The leaf solar transmittances are shown in Table 5. Results show that increasing leaf layers will

decrease the solar transmission. In terms of solar reduction by the different number of leaf layers,

Table 8 demonstrates the effect of solar shading by leaves.



Number of leaf layers 1 2 3 4 5

Percentage of solar reduction 37% 66% 75% 79% 86%

Table 8: Solar reduction by Virginia Creeper leaves

Even one layer of leaf can reduce 37% of the incident solar radiation, which is about one-third of

original incident beam. Up to 86% of solar can be removed by a layer of five leaves. This means that

the bioshader can block more solar radiation with better foliage. The entire bioshader comprises

areas of various leaf layers. If the area of five-layer leaves is very extensive, the shading effect will be

very substantial because 86% of reduction can be achieved by five-layer leaves. On the contrary,

bioshader with mostly one-layer leaves will not block as much solar as that with more five-layer

leaves. This also agrees to the performance of the bioshader in improving the temperature and

relative humidity with increasing growth of the climbers.

7.3 Limitation to bioshader experiment

There are limitations to the bioshader experiment, which are summarised below.

• The plant framework is limited to a size of lattice of 150 by 200mm. This size is too small to

be used by plants such as Virginia Creeper which is used in this bioshader experiment. Due

to the fact that time is limited for the plants to establish and cover the glazed façade, this

small size lattice is required. In reality, this size can be increased according with different

growth rate of climbing plants.

• The four Virginia Creeper plants bought for this experiment are fairly established and they

were already about a one-metre tall when first planted. Although they were not leafy at all

when they were bought, they were already well established and so they can perform their

ability to shade with their foliage of leaves. Ideally, the experiment should employ young

plants in order to monitor fully the growth rate of the bioshader.

• The sensors used in this experiment were chosen by the Durabuild team and also from

experienced technical staff from the School of the Environment in the University of Brighton.

The number of sensors used is restricted, partly by cost, and also by the mountable space

within the test and control offices. The fixings for some sensors, especially the temperature

and relative humidity sensors, require particular attention to position where no direct sunlight

can reach. Thus locations of the sensors may not be the ideal positions.



• Fixings and working on the sensors were also difficult, as those offices were occupied. Staffs

open and close door every now and then during office hours, this affected the ventilations

rates within the test and the control rooms and so had impact on the results.

• The accuracy of the sensors may also affect the data collected in the bioshader experiment.

The sensors used in this experiment can be of better accuracy, but owing to the high prices

of these sensors, cheaper option may be used. This will also affect the accuracy of data

collected.

• The methodology in assessing the leaf solar transmittances is based on moving the solar flux

sensor over certain areas of the bioshader. The accuracy of this method is limited due to the

fact that a lot of diffuse or indirect solar radiation will affect the solar flux sensors reading.

• The filtration of the outliner data (as shown in Appendix B) for solar transmittances was

rather subjective. The selection of data was purely depends on the view on the graph to

determine which are the times of data to be included for calculation for the solar

transmittance.



8.0 Conclusion

The growing global awareness of energy conservation has delegated a big challenge to building

designers to control the use of energy in buildings. With the emerging hotter summers, there is an

increasing demand for buildings that are able to maintain the required internal thermal comfort

without resorting to the use of air conditioning in the summer. One sustainable design option is to

implement effective natural ventilation coupled with external shading devices to reduce solar gains.

The performance of this kind of design can be further enhanced by the use of live plants acting as the

shading device.

There is an increasing scope of using vegetation as climatic modifiers in the built environment; such

design is often termed as bioclimatic design. The bioshader described in this report has

demonstrated the successful use of such design option suitable for use to office buildings with glazed

façade. The proposed bioshader has been tested and applied to an office in the University of

Brighton. Its performance was monitored and subsequently analysed in this case study report.

The room temperature of the university office was greatly reduced on most of the hot summer

afternoons. Peak temperature reduction reached 5.6°C in the office with the bioshader setup. Room

temperatures were at least lowered by 3.5°C over each summer afternoon from July to September.

Relative humidity levels in the test room (with bioshader) and the control room (without bioshader)

were also compared. The humidity level in the test room was permanently higher than that of the

control room, demonstrating the added value of using live plants to bring extra moisture into the dry

environment of the office. From July to October, the bioshader increased the test room relative

humidity level from the range of 13.7% to 4.9%.

Calculations from the experimental results show that the leaf solar transmittances are between 0.43

to 0.14 for one to five leaf layers. These correspond to a solar reduction of up to 37% by only one

layer of Virginia Creeper leaf, 66% solar reduction by two layers, 75% by three layers, 79% by four

layers and 86% by five layers. By looking at these solar reduction figures, it is fairly obvious that

leaves or plants can block a considerable amount of excessive sunlight into buildings. Solar radiation

falling onto conventional metal shading devices will heat up the temperature of the device. Heat can

then be re-radiated from the metal shading devices into the surrounding air before entering the

building. Whereas the bioshaders reflect, absorb and transmit proportions of the incident solar

radiation without warming up the microclimate.

When applying bioshaders onto buildings, it is necessary to carefully consider the growth of the

plants. The bioshader shading performance increases with its foliage and coverage over the glazed

area. Building designers may wish to adopt established plants rather than newly grown climbers on



the framework in order to achieve a minimum level of shading effect. Implantation of climbers would

be best to do as soon as the framework is ready to allow additional time for the plants to establish.

Plants are living organisms which are not under control by human beings. Their growth rates are also

affected by a lot of other environmental factors such as weather conditions. Therefore, the overall

development of the bioshader on the framework is not within exact prediction. This may form another

limitation when using plants with buildings. The bioshader design described in this report is a new

and novel idea. There would be a lot of improvements to its design by initiating further research in

this area.



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10.0 Appendix

Appendix A: Solar adjustment for vertically fixed sensors

N

S

225°

True bearing of the experiment location is 225º

This means the orientation of the bioshader is 45º west from south.

Geographic details of Brighton:

Latitude: 50º50’N

Longitude: 0º08’W

Details of this obtained from:

www.astro.com/atlas

www.weatherman.me.uk

Terms used in (Sukhatme, 1996):

Hour angle is the time in degree of the earth. One circulation of the earth is one day and so one day

is 360 degree. That means for every hour of the day, the earth will turn 15 degree. This also means

that in terms of minutes calculation, the hour angle will be the number of minutes from the true solar

time noon * 0.25

Local apparent time is the true solar time, which is in determination by the position of the sun

Mean solar time is the time calculated by lunar adjustment for longitudinal displacement from local

time zone.

Radian is another form of measure in degree. One 360 degree is equals to 2π radians. So 1 radian =

57.29°

Solar radiation geometry

In order to find the beam energy falling on a surface having any orientation, it is necessary to convert

the value of the beam flux coming from the direction of the sun (I) to an equivalent value

corresponding to the normal direction to the surface (I cosθ), where θ is the angle of incidence.

Cross section view of the experiment:


http://www.astro.com/atlas

http://www.weatherman.me.uk/


Radiation data from dome solarimeter (I)

Horizontal component (I cos θ)

θ

Wall azimuth

This is the angle made in the horizontal plane between the line due south and the projection of the

normal to the surface on the horizontal plane. It can vary from -180° to +180°. The convention in this

formula calculation is that the wall azimuth is positive if the normal is east of south and negative if

west of south.

N

S

-45°

N

S

+60°

Hour angle

It is an angular measure of time and is equivalent to 15°per hour. It varies from -180° to +180°. The

convention of measuring it from noon based on local apparent time (LAT), being positive in the

morning and negative in the afternoon.

Time Hour Angle 00:00 +180° 01:00 +165° 02:00 +150° 03:00 +135° 04:00 +120° 05:00 +105° 06:00 +90° 07:00 +75° 08:00 +60° 09:00 +45° 10:00 +30° 11:00 +15° 12:00 0° 13:00 -15° 14:00 -30° 15:00 -45°

N

S

±180° 00:00

06:00

12:00

18:00 +90°

0°

-90°



In order to change the time in the data to hour angle for the formula

calculation, the following needs to apply.

As for each hour, it is 15°. Therefore, the change in time from 00:00 to

that hour X is equal to ∆t

To change ∆t into terms of hour angle, multiply with 15. Say it is 03:00,

so it will be 45°. However, this is only an angular measure away from midnight. In order suit back to

the hour angle corresponding to the table beside, the formula needs to apply:

16:00 -60° 17:00 -75° 18:00 -90° 19:00 -105° 20:00 -120° 21:00 -135° 22:00 -150° 23:00 -165° 24:00 -180°

[(00:00 – X) * 15] +180

Example:

Three in morning: [(00:00 – 03:00) * 15] +180 =135°

Ten at night: [(00:00 – 22:00) * 15] +180 = -150°

x = time (in hour) y = hour angle (°)

y = -15x + 180°

Declination δ

δ is the angle made by the line joining the centres of the sun and he earth with its projection on the

equatorial plane. Its arises by the virtue of the fact that the earth rotates about an axis which makes

and angle of approximately 66.5° with the plane of its rotation around the sun. The declination angle

varies from a maximum value of +23.45° on June 21 to a minimum value of -23.45° on December 21.

It is zero on the two equinox days of March 21 and September 22.

Solar correction by Sukhatme 1996:

To change degree to radian (cos excel calculated in radian)

Radian = x degree / 2π = x degree / 57.29577951

21-Jun 172nd day of the year

For declination δ formula:

23.45 sin (360/365 *(284+n)) in degree

23.45 sin [(360/365* (284+n))/57.29] in radian

23.45 *sin (449.75)

Formula for angle of incidence (from Sukhatme 1996):

cosθ = sinΦ (sinδ cosβ + cosδ cosγ cosω sinβ) + (cosΦ (cosδ cosω cosβ - sinδ cosγ sinβ) + cosδ sinγ sinω sinβ Where:

θ = angle of incidence



Φ = latitude

δ = declination, which is the angle made by the line joining the centres of the sun and the earth with

its projection on the equatorial plane.

β = slope of the surface, if vertical surface is 90deg

γ = wall azimuth

ω = the hour angle, which is 15 degree per hour. At noon, it is 0 deg. At 0900 is 45 deg. At 1500 is -

45deg

The vertical solar component falling onto the horizontal sensor is:

Solar radiation data logged by the data logger * cos θ



Appendix B: Graphs for leaf solar transmittances

Solar transmittance by 1-layer of Virginia Creeper leaf

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0 100 200 300 400 500 600 700 800

Number of readings

Sola

r tra

nsm

ittan

ce

0.43

Figure 42: Solar transmittance for 1-layer of Virginia Creeper leaf

Solar transmittance by 2-layers of Virginia Creeper leaf

0.00

0.20

0.40

0.60

0.80

1.00

1.20

0 50 100 150 200 250 300

Number of readings

Sola

r tra

nsm

ittan

ce

0.34

Figure 43: Solar transmittance for 2-layers of Virginia Creeper leaf



Solar transmittance by 3-layers of Virginia Creeper leaf

0.00

0.20

0.40

0.60

0.80

1.00

0 50 100 150 200 250 300 350

Number of readings

Sola

r tra

nsm

ittan

ce

0.25


Solar transmittance for 4-layers of Virginia Creeper leaves

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

0 50 100 150 200 250 300 350 400

Number of readings

Sola

r tra

nsm

ittan

ce

0.21




www.durabuild.org

Solar transmittance for 5-layers of Virginia Creeper leaves

0.00

0.10

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

0 50 100 150 200 250 300

Number of readings

Sola

r tra

nsm

ittan

ce

0.20 0.14


Acknowledgements:

Dennis Osborne and Nikki Errington from Mendip Manufacturing Agency Limited (Jakob® Inox Line Company) for the provision of the stainless steel framework. Peter Jakob for the interesting pictures that he had provided. Estates Department of the University of Brighton for the help on provision of the experimental site. All technical staff in the school for their assistance in the experimental setup. Bruno Stagno and Enrique Browne for their provisions of building pictures and plans.

Project team

Professor Andrew Miller E-mail: [email protected] Tel: 44 (0)1273 642380

Dr Kenneth Ip E-mail: [email protected] Tel: 44 (0)1273 642381

Ms. Kath Shaw E-mail: [email protected] Tel: 44 (0)1273 643455

Ms. Marta Lam E-mail: [email protected] Tel: 44 (0)1273 643455

University of Brighton School of the Environment Cockcroft Building Lewes Rd Brighton BN2 4GJ United Kingdom

of 57

mailto:[email protected]





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