an analysis of heat insulation efficiency of building outer skins used for green building

7/27/2019 An analysis of heat insulation efficiency of building outer skins used for green building

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through solar energy acumulation into theearth over millions of years.1 The buildingsector is the largest energy consumer follow-ing the industrial sector. In many countries,the energy required for space heating andcooling in buildings has the highest share ofall. In Taiwan, the energy used to constructand operate buildings constitutes 45% of thetotal energy use. Energy saving and the effectiveusage of energy are very important in Taiwansince it imports most of its energy. For theabove reasons, it is clear that effective thermalprotection in building sector plays an importantrole towards the reduction of energy consump-tion for space heating and cooling.2

Thermal insulation materials like any othernatural or man-made materials exhibit tem-perature-dependent properties that vary withthe nature of the material and the influenc-ing temperature range. The impact of operat-ing temperature on the thermal performanceof insulation materials has been investigatedby many studies. The results indicate thatinsulation materials subject to high tempera-ture have higher thermal conductivity andtherefore higher envelope cooling load withvarying degrees depending on the type ofinsulation material.3 Building insulation willreduce the operational cost of space heatingat the expense of an increase in the initialinvestment by the added insulation material.4

Many researches have been carried out onthis subject to investigate the effectiveness ofbetter thermal insulation for existing build-ings to reduce energy consumption.58 Yoonet al.5 determined the impact of variousinsulation systems on the total cooling loadof the cool storage structures with particularconsideration given to the product thermalmass to find optimal insulation thicknessesfor each envelope component for variousclimatic locations in Korea. Al-Sallal6 com-pared two types of roof insulation (polysty-rene and fiberglass) in warm and cold climatesand found that the payback period in coldclimates is shorter than that in warm climates.

On the other hand, to mitigate globalwarming, every government in the world hastried very hard to reduce the CO2 emissions.The Taiwanese government hopes to achievethe targets of 16% and 28% decrement ofCO2 emissions in 2010 and 2020, respectively(taking 1997 as the baseline). Reinforcedconcrete structures are widely used by thebuilding industry in Taiwan. However, theconstruction materials used in above struc-tures are one of the important reasons thatcaused the CO2 emissions. Besides, improperexploitation of river sands will change theriver morphology in certain riverbed sectionsand lead to the depletion and destructionof the embankment foundation.9 This willusually cause significant threat to the humanlife and losses of property. However, thedesign of green building, such as steelframe building, can reduce not only the useof architectural materials such as sand,cement and aggregate but also shorten theworking hours and reduce the emissionvolume of CO2.

A group of new apparatuses known ascontact transient methods has recentlybecome very attractive and popular forall types of materials because they can beused to measure several thermal propertiessimultaneously or separately.1013 A so-calledhot box method (HBM) was adopted inthis study to investigate the heat-insulatingperformance of the building skin material.Nowadays, the hot box method has beenwidely used to obtain necessary data to mea-sure the thermal conductivity (k) and thermaltransmission rate (U) of the material. Byinferring the type of heat-transfer coefficient,the test method will be classified according tothe following: (1) the heating type of thesubject, (2) the heat-conducting process,(3) the direction of conductive thermal currentthrough the subject, (4) the shape of thesubject, (5) the thermal current volume mea-suring method, and (6) the functional relation-ship between thermal current and time.

408 An analysis of heat insulation efficiency of building outer skins used for green building


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There are several studies dealing with theenergy efficiency of the different componentsof buildings such as the cladding, electrical,structural and mechanical systems.1416 Inbuildings, most of the energy is used forheating and cooling; therefore, many studiesare targeting on the improvement of heatinsulation systems.

The use of multi-layer skin wall is suggestedto be an effective way to reduce the buildingssolar heat gain.17 Typically, the multi-layerskin wall comprises the inner layer, supportlayer and outer layer elements. Besides, itcan be classified into three types: the airpermeable type, the ventilation type and theairtight air layer type according to the type ofsupport layer. Furthermore, the space of thesupport layer also provides the thermal buoy-ancy effect similar to a thermal chimney;therefore, it plays a key role in the indoornatural ventilation effect.18 Researchers havesuccessively demonstrated that these struc-tural variables can have significant impact onthe thermal performance. Measurements ofreal samples of anisotropic building structuresare thus necessary to support thermal design.As a consequence of the wide ranges of thermalproperties, a measurement method has to beselected depending on the following criteria:possible sample size and shape, temperaturerange, and thermal conductivity range.1921

Multi-layer facades are assuming an ever-greater importance in modern building prac-tices. They are already a common feature ofarchitectural competition in Europe; however,relatively few buildings have actually beenrealized, and there has been too little experi-ence with how they actually behave inoperation.2224

A green building, also known as a sustain-able building, is a structure that is designed,built, renovated, operated or reused in anecological and resource-efficient manner.Green buildings are designed to meet cer-tain objectives such as protecting occupanthealth; improving employee productivity;

using energy, water and other resources moreefficiently and reducing the overall impact tothe environment. A green building is anopportunity to use our resources efficientlywhile creating healthier buildings. It providescost savings to all over the world throughimproved human health and productivity,lower cost building operations and resourceefficiency and it moves us closer to asustainable future.

The objectives of this research are toinvestigate the heat insulation efficiencies ofbuilding outer skins used in the green build-ings. The results will support us with usefulinformation to understand the heat insulationproperties of building skin and to help the

building industry to choose the most suitablematerials.

2 Materials and methods

2.1 MaterialsIn this study, a total of 39 groups of

building skin material were tested: 10 groupsof Taiwan-made single-layer materials, 25groups of multi-layer materials made in this

study and 4 groups of overseas multi-layermaterials. The names and the specifications ofmaterials used in the experiment are shown inTable 1. The sizes used in the study togetherwith the physical properties, mechanical char-acteristics and unit price used by the outerwall materials, middle supporting/bearingmaterials, inner wall materials and overseasmaterials are shown in Tables 25.

2.2 MethodsThe experimental devices adopted in the

study were Hot Box Method.25 The entireexperimental box is divided into three sectionsto emulate the ambient conditions, indoorconditions and experimental composite layerconfigurations; see Figure 1. The outdoor sideis provided with one unit of heater and fan,whereas the indoor side is also provided witha cooler and fan so that the air temperature

W-S Hou et al. 409


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and the air-current speed of the respectivesections can be controlled independently. Thesubject was placed at the center of support

frame where the heat can be insulated allaround. During the experiment, the spacebetween the subject and the support framewas configured into airtight status to com-pletely isolate the air current of the indoorsection and the outdoor section so the setconditions of both sides would not affect eachother. The controllable temperature range ofthe indoor side was 58C408C, and thestationary wind speed was 00.5 m/s. As forthe outdoor side, the controllable temperaturerange of the indoor side was 08C608C; thestationary wind speed was 03 m/s; and themaximum wind speed could reach as high as10 m/s. The air temperature of the outdoorside was controlled by using the heater andthe cooler alternatively to achieve accuratetemperature adjustment and control. A halo-gen lamp was used to simulate heat radiation,and the power provider was used to adjust

current levels to control the heating capacity.The refrigerating chamber provided the lowtemperature to the cooler, and the tempera-

ture of air inside the chamber was adjusted bya control panel. As for the air-current control,the inverter was used to control the fan speeddirectly to achieve the required air speed.

The experiment was performed in theconstant temperature room and heating boxto simulate the high temperature of summerin Taiwan. The temperature was controlledbetween 25 18C40 18C and that at thelower temperature side was over 10 18C.Furthermore, the temperature of the air in theheating box, constant temperature room andlow temperature room were tested first, andthen the surface temperature and humidity ofthe skin material subject were also measuredto understand the impact on the heat insula-tion under varied temperature levels. Duringthe experiment, the CR-10X Data Loggerfrom Campbell Scientific, Inc. was used; itwas designed with several kinds of input/

Table 1 Experimental materials and specifications

No. Material Size (cm2

) Thickness

(mm)

Cost

(USD/m2)

Producing countries

and the scope of application

a Air-permeable colour-

corrugated steel plate

80 80 5 6.1 Taiwan, outer wall material

b Weather board 80 80 6.5 31.7 Taiwan, outer wall materialc Colour corrugated steel plate 80 80 3 5.5 Taiwan, outer wall materiald Hollow cement board 80 80 20 84.8 Taiwan, outer or inner Wall

materiale Conventional steel bearing plate 80 80 T 1.5/W 5 15.8 Taiwan, supporting materialf FRP hollow board 80 80 70 48.5 Taiwan, supporting materialg Gypsum board 80 80 10 2.4 Taiwan, inner wall materialh Calcium silicate board 80 80 6 4.1 Taiwan, inner wall materiali Magnesium oxide board 80 80 6 2.4 Taiwan, inner wall material

j Paint-baking metal plate

4 100 k Rock wool

Paint-baking metal plate

80 80 12 5.8 Germany, multi-layer Skinmaterials

k Paint-baking metal plate

2 100 k Rock wool Paint-baking metal plate

80 80 52 18.2-24.2 Germany, multi-layer skinmaterials

l Paint-baking metal plate

PU Paint-baking metal plate80 80 52 48.5-63.6 Germany, multi-layer

skin materialsm Paint-baking metal plate Air-layer

ABS generated by construction

plastics Paint-baking metal plate

80 80 52 48.5-63.6 Germany, multi-layerskin materials

Note: Cost: materials wage, USD: United States dollar, NTD: New Taiwan Dollar 1:33.



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Table

2

Externalwallmaterialproperties,madeinTaiwan

MaterialItem

a.

b.

c.

d.

Photo

MaterialProperties

T

hickness(cm)

0.5

0.65

0.3

2

Q

uality(kg/m2)

150

20

200

75

M

aterialcomposition

Electropla

tingplate

PUfoamboard

Electroplatingplate

Cement,asbestos

M

aterialcharacteristics

Steelcorr

ugated

sheetwithventilation

holes

Goodaesthetics

Largespan,Fast

construction

Withairlayer

(Thickness1.5cm)

C

onstructability

*^

*^

*^

*

W

eatherability

*^

*^

*^

*^

F

ireresistance

Fireproof

level1

(CNS6532

)

Fireprooflevel1

(CNS6532)

Fireprooflevel1

(CNS6532)

Fireprooflevel1

(CNS6532)

W

aterproof

*

*^

*

*

A

bsorbent

*

*

*

4

S

oundproofing

*^

*

4

*

Insulation

*^

*

4

4

S

hock

4

*

4

*

H

anging

4

*

4

*

F

ixationmethod

Bolt/self-tapping

screw

Bolt/self-tapping

screw

Bolt/self-tapping

screw

Bolt/self-tapping

screw

E

nvironmental

p

rotection

*

*

*

4

Materialprice

(USD/m2)

6

.1

31.7

5.5

48.8

Universal

4

*

4

4

4

Note:*^:Excellent,*:Good,4:Fair.


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output patterns in addition to its automatictesting and record storing capability, whichwas used to log the voltage sensed by theinstrument. The measuring instrument usedfor the experiment was a T-type thermocou-ple for measuring dry bulb/wet bulb temper-ature; in addition, the TES-1360 DigitalTemperature/Humidity Gauge was also usedto measure the ambient humidity. The mea-surement steps are explained as follows:Firstly, perform the cooling and heatingcalibration of the T-type thermocouple andthen implement the experimental box in theconstant temperature room. To ensure thatthe mock-up house can be affected by the

external environment, the comparative testingand experiment can be conducted for themock-up house. The temperature and humid-ity measured from the thermocouple wire andtemperature/humidity gauge measuringpoints can be registered in the CR-10X DataLogger for future comparison. When theexperiment begins, seal the heat contact ofthe thermocouple with waterproofing tape onthe surface center of the heating box and thecooling box. Place one piece of the subject inbetween the heating box and the cooling boxand then fix the entire experiment boxsecurely. After fixing, seal with waterproofingtape to prevent air convection at the lateral

Table 3 Supporting material properties, made in Taiwan

Material Item e. f.

Photo

Material Properties Thickness (cm) Thickness 15 mm,

Pitch 50 mm

Thickness 8 mm,

Pitch 70 mmQuality (kg/m

2) 19.9 15.6

Material composition Galvanized steel plate PVC (non-flammable

high polymer components)Material characteristics Prefabricated / quality

and stability

Prefabricated / quality

and stabilityConstructability * *Weather ability * *

Fire resistance Fireproof level 1

(CNS6532)

Fireproof level

1 (CNS6532)Waterproof * *Absorbent * *Soundproofing * *

Insulation * *Shock * *

Hanging * *Fixation method Bolt / self-tapping screw Bolt / self-tapping

screwEnvironmental

protection

* *

Material price (USD/m2) 15.8 48.5

Universal * *

Note: *: Excellent, *: Good, 4: Fair.



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side of the subject. When the stabilizedstatus, over 258C, of the simulated outdoortemperature is reached, test the temperatureand the electric power of the main heater.

The stabilized status means that under theconditions of not changing the set power ofthe main heater, the temperature difference ofthe subject per hour is less than 1%. The datalogger receives one count of experimentalfigures at 1-min intervals. When the obtainedexperimental temperature of the outdoorside is over 408C and that of the indoor sideis below 108C, the test ends and the figure

analysis proceeds to calculate the heatinsulating performance of the subject. Afterthe internal temperature of the constanttemperature room resumes to normal, thenext group of the experiment continues tominimize the accumulation of thermal energyto cause the deviation of the experimentalfigures.

Each material was coded from a to m,totaling 13 groups, whereas the compositematerials composed of individual materialwere coded from 1 to 25, totaling 25 groups.Described below is the arrangement of the

Table 4 Supporting material properties, made in Taiwan

Material Item g. h. i.

Photo

Material Properties Thickness (cm) 1 0.6 0.6

Quality (kg/m2

) 1.1 1.16 1.04

Material composition Natural gypsum,

fiber materials

Calcium oxide,

Quartz

Magnesium oxide (MgO),

Magnesium chloride (MgCl2),

Fiber materialsMaterial characteristics Natural gypsum,

No pollution

Fireproof, On toxic,

Smokeless

Sheet flexibility, flexible

Constructability * * *Weather ability * level 3$4(CNS3839) *Fire resistance Fireproof level

1 (CNS6532)

Fireproof level

1 (CNS6532)

Fireproof level 1 (CNS6532)

Waterproof 0.6% (CNS4459) 8.64% (CNS3903) 8.8% (CNS3903)

Absorbent * 46.34% (CNS13778) 36.7% (CNS13778)

Soundproofing * 55db *

Insulation 0.057 0.0916(CNS7333) 0.094(CNS7333)

Shock * *(CNS13788) *Hanging * * *Fixation method Self-tapping

screw

Self-tapping screw Self-tapping screw

Environmental

protection

* * *

Material Price(USD/m2

) 2.4 4.1 2.4Universal * * *

Note: *: Excellent, *: Good, 4: Fair.

W-S Hou et al. 413


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Table

5

Multi-layerskinmaterialsproperties,madeoverseas

MaterialItem

j.

k.

l.

m.

Photo

MaterialProperties

T

hickness(mm)

52

52

52

52

Q

uality(kg/m2)

16.65

16.65

16.65

16.65

M

aterialcomposition

Plate

Insu

lation

material

Plate

Insulation

material

Plate

Insulation

material

Plate

Insulation

material

M

aterial

characteristics

Multi-layer

sandwichplate

Multi-layer

sandwich

plate

Multi-layersandwich

plate

Multi-layer

sandwichplate

C

onstructability

*^

*^

*^

*^

W

eatherability

*^

*^

*^

*^

F

ireresistance

Fireprooflevel

1(CNS6532

)

Fireprooflevel

1(CNS6532)

Fireprooflevel

1(CNS6532)

Fireprooflevel

1(CNS6532)

W

aterproof

*^

*^

*^

*^

A

bsorbent

*^

*^

*^

*^

S

oundproofing

*

*

*

*

Insulation

*^

*^

*^

*^

S

hock

*^

*^

*^

*^

H

anging

*

*

*

*

F

ixationmethod

Bolt/Self-tapping

screw

Bolt/Self-

tappingscrew

Bolt/Self-tapping

screw

Bolt/Self-tapping

screw

E

nvironmental

p

rotection

*^

*^

*^

*^

Materialprice

(USD/m2)

63.6

63.6

63.6

Universal

*^

*^

*^

Note:*^:Excellent,*:Good,4

:Fair.


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measuring point for the experimental mod-ules; for the arrangement of thermocouplewires, please refer to CNS10523. For structuralmechanic analysis, to study the mechanicbehavior of each material and module underdifferent combinations for the selected multi-layer skin (outer wall material plus supportingmaterial plus inner wall material), this studyused the single-layer material stress figuresindicated in Table 2 to Table 5 as provided bythe vendor. Furthermore, the ProfileTransformation Method26 was used for anal-ysis and calculation to understand the actualstress behavior of different modules in themulti-layer skin. Because the characteristics ofmechanic behavior of multi-layer skin aresimilar to that of the curtain wall, the windforce is normally taken as the main investiga-tion target for the surface of the vertical wallpanel; as for the seismic force, consideration isgiven to the inter-layer displacement at the wallbody connecting area. As such, the stressbehavior was calculated for the 25 groups ofmulti-layer skin modules in this research, andthe results can be used as a reference forstructural technicians to calculate the skinsresistance against the wind load and inter-layer displacement during the practicalcalculation.

2.3 Data analysis

2.3.1 Heat-insulating capacityIn this study, the temperature and humidity

of measuring points can be registered in the

CR-10X Data Logger for further calculation.With the values of temperature, humidity andPsychrometric Chart, the enthalpy can thenbe obtained. The heat-insulation abilitycan then be calculated using the followingequation:

outer enthalpy indoor enthalpy=

outer enthalpy 100 % 12

2-1

2.3.2 Vapor transmission volumeThe theory for calculating the stabilized

vapor transmission rate is similar to the heattransfer behavior in which the moisture in thematerial flows from the higher pressure steamto the lower one and the ways of flow aredetermined by means of water, steam andsteam and water.9 Shown below is the calcu-lation rule:

Wf1 f2

R0 A U

0

f1 f2Ag=h 2-2

R0

1

h0

1

X

r0

X

r0

a 1

h0

2

m2hmmHg=g

2-3

U0

1

R0 g=m

2hmmHg 2-4

where W wet current, also called the vaportransmission volume (g/h); f1 high-pressureside steam pressure (mmHg); f2 low-pres-sure side steam pressure (mmHg); R totalwet resistance, also called the vapor trans-mission resistance (m2h mmHg/g); U wettransmission coefficient, also called the vaportransmission coefficient (g/m2h mmHg);

Simulate outside

temperatureSkin material subject

Data Logger

The material subject on both sides of the layout of 9 points to the

amount of testing the surface of dry bulb and wet bulb temperature

Simulate insidetemperature

Figure 1 Schematic diagram of experimental box.The material

subject on both sides of the layout of 9 points to the amount of

testing the surface of dry bulb and wet bulb temperature

W-S Hou et al. 415


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11/17

Table

6

Comparisonofheatcapacityofskinsmaterials

Materialtype

Average

temperature

(8C)

Relativehumidity

(RH)(%)

Indoorandouter

enthalpy(kj/kg)

Insulation

ability(%)

Moisture

permeability

(g/h)

C

ooling

lo

adQ

(W)

Cost

(USD/m2)

Outdoor

air

Indoorair

Indoorinitial

moisture

Indoorlast

moisture

Outdoor

Indoor

a.

26.1

19.8

98.2

55.1

80.2

39.4

50.9

0.015

247.7

6.1

b.

29.8

19.3

46.5

34.7

61.1

31.7

48.2

0.007

0.2

31.7

c.

29.0

19.2

61.6

26.3

68.7

28.5

58.5

0.015

313.9

5.5

d.

27.4

27.1

98.7

97.1

85.8

83.9

2.3

0.034

1.1

84.8

e.

28.3

20.4

98.5

33

90.3

33.0

63.5

0.020

374.4

15.8

f.

34.3

21.4

71.7

54.3

97.9

43.5

55.6

0.012

0.4

48.5

g.

25.7

24.5

99

94

75.9

73.5

3.2

1.622

0.3

2.4

h.

26.9

16.8

91.4

39

79.5

28.6

64.1

0.283

1.6

4.1

i.

31.1

25.6

76.8

58.7

87.7

56.4

35.7

0.238

0.7

2.4

j.

31.5

21.0

83.6

36.9

94.8

35.5

62.5

0.025

518.6

5.8

k.

27.3

11.7

97

73

84.4

27.4

67.6

0.018

801.0

18.2-24.2

l.

28.2

12.7

93.4

75.1

86.4

30.1

65.2

0.010

1020.0

48.5-63.6

m.

28.6

12.3

58.7

84.7

65.5

31.4

52.1

0.051

1018.3

48.5-63.6

1.(a

e

d)

27.9

23.1

99

92

88.6

65.0

26.7

0.003

505.6

106.7

2.(a

e

g)

25.8

17.8

95.5

79

77.1

43.4

43.7

0.008

513.6

24.2

3.(a

e

h)

25.8

18.1

96

78.5

77.3

44.0

43.1

0.006

490.5

25.9

4.(a

e

i)

28.0

23.4

93

90

85.0

65.0

23.5

0.011

449.9

24.2

5.(a

fg)

30.8

24.0

94

89

95.5

69.2

27.6

0.003

263.3

57.0

6.(a

fh)

34.4

20.4

38

25

57.6

33.9

41.1

0.012

422.4

58.6

7.(a

fi)

32.2

24.7

96

76

108.1

62.5

42.2

0.005

254.3

57.0

8.(b

e

g)

32.3

22.2

99

69

111.7

51.7

53.7

0.005

312.4

49.8

9.(b

e

h)

28.6

17.9

94

76

88.8

42.5

52.2

0.010

387.6

51.5

10.(b

e

i)

33.2

20.8

98

82

115.6

52.8

54.3

0.010

447.9

49.8

11.(b

f

g)

29.0

15.3

94

72

90.2

35.1

61.1

0.005

2.4

82.6

12.(b

f

h)

36.3

25.8

97

94

134.8

76.2

43.4

0.012

2.0

84.2

13.(b

f

i)

32.3

20.4

95

70

108.0

47.1

56.4

0.006

1.8

82.6

14.(c

e

g)

30.0

18.2

93

75

94.7

43.2

54.4

0.017

819.5

23.7

15.(c

e

h)

31.6

19.0

95

53

104.0

37.5

63.9

0.001

894.5

25.4

16.(c

e

i)

33.3

20.8

97

65

115.8

46.2

60.1

0.010

940.1

23.7

17.(c

fg)

30.5

20.4

92

74

96.5

48.7

49.5

0.012

355.9

56.4

18.(c

fh)

28.0

19.5

94

72

85.7

45.5

46.9

0.008

353.0

58.1

19.(c

fi)

25.9

12.0

93

75

76.4

28.4

62.8

0.003

508.7

56.4

20.(d

e

g)

30.5

21.4

97

85

100.2

56.0

44.1

0.023

332.5

103.0

21.(d

e

h)

33.5

21.1

91

74

111.3

50.7

54.5

0.016

423.7

104.7

22.(d

e

i)

32.0

17.8

99

62

110.0

37.8

65.6

0.008

499.6

103.0

23.(d

f

g)

27.4

16.5

94

75

83.0

38.9

53.2

0.006

9.0

135.8

24.(d

f

h)

36.0

23.8

92

84

127.1

63.6

50.0

0.012

10.5

137.4

25.(d

f

i)

30.8

20.1

95

70

100.1

46.3

53.8

0.009

8.4

135.8


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Table

7

Comparisonofmoisture-permeableresistanceofskinsmaterials

Materialtype

Moisture-permeable

resistanceR0m

2h

mmhg/g

Thevaporpressing

athigh-pressuresid

e

f1mmhg

Thevaporpressing

atlow-pressureside

f2mmhg

moisture-permeable

CoefficientU

g/m2h

mmHg

vaportransmission

volumeg/h

Cost(USD/m2)

a.

208.33

17.93

12.94

1/20

8.33

0.015

6.1

b.

500

15.67

9.98

1/50

0

0.007

31.7

c.

208.33

11.26

6.41

1/20

8.33

0.015

5.5

d.

108.7

29.45

23.75

1/10

8.7

0.034

84.8

e.

208.33

17.32

10.79

1/20

8.33

0.020

15.8

f.

500

26.40

16.93

1/50

0

0.012

48.5

g.

2.32

27.32

21.44

1/2.

32

1.622

2.4

h.

20.83

20.48

11.27

1/20

.83

0.283

4.1

i.

20.83

25.02

17.28

1/20

.83

0.238

2.4

j.

208.71

23.37

15.19

1/20

8.71

0.025

5.8

k.

208.68

24.30

18.40

1/20

8.68

0.018

18.2-24.2

l.

208.45

24.52

21.15

1/20

8.45

0.010

48.5-63.6

m.

208.45

29.44

12.75

1/20

8.45

0.051

48.5-63.6

1.(a

e

d)

525.36

24.09

21.47

1/52

5.36

0.003

106.7

2.(a

e

g)

418.98

25.99

20.64

1/41

8.98

0.008

24.2

3.(a

e

h)

437.49

23.91

19.57

1/43

7.49

0.006

25.9

4.(a

e

i)

437.49

30.69

23.17

1/43

7.49

0.011

24.2

5.(a

fg)

710.65

24.83

21.55

1/71

0.65

0.003

57.0

6.(a

fh)

729.16

18.99

5.50

1/72

9.16

0.012

58.6

7.(a

fi)

729.16

25.47

19.87

1/72

9.16

0.005

57.0

8.(b

e

g)

418.98

31.45

28.23

1/41

8.98

0.005

49.8

9.(b

e

h)

437.49

24.05

16.89

1/43

7.49

0.010

51.5

10.(b

e

i)

437.49

32.91

25.76

1/43

7.49

0.010

49.8

11.(b

fg)

1002.32

23.71

15.68

1/10

02.32

0.005

82.6

12.(b

fh)

1020.83

48.54

28.65

1/10

20.83

0.012

84.2

13.(b

fi)

1020.83

30.19

20.14

1/10

20.83

0.006

82.6

14.(c

e

g)

418.98

27.98

17.02

1/41

8.98

0.017

23.7

15.(c

e

h)

437.49

21.27

20.52

1/43

7.49

0.001

25.4

16.(c

e

i)

437.49

28.20

21.07

1/43

7.49

0.010

23.7

17.(c

f

g)

710.65

29.52

15.93

1/71

0.65

0.012

56.4

18.(c

f

h)

729.16

25.55

16.08

1/72

9.16

0.008

58.1

19.(c

f

i)

729.16

22.36

18.91

1/72

9.16

0.003

56.4

20.(d

e

g)

319.35

31.18

19.60

1/31

9.35

0.023

103.0

21.(d

e

h)

337.86

30.38

22.15

1/33

7.86

0.016

104.7

22.(d

e

i)

337.86

24.05

19.88

1/33

7.86

0.008

103.0

23.(d

fg)

611.02

22.40

16.68

1/61

1.02

0.006

135.8

24.(d

fh)

629.53

40.42

28.94

1/62

9.53

0.012

137.4

25.(d

fi)

629.53

26.71

17.83

1/62

9.53

0.009

135.8


13/17

3.2 Moisture-permeable resistance

The results of the moisture-permeableresistance for the skin material are shown inTable 7 and indicated that:

(1) Among them, Item 15 (colour corru-gated steel plate conventional steelbearing plate calcium silicate board)present the best moisture permeabilityresistance, which is 0.001 g/h, and fol-lowed by the l group (paint-bakingmetal plate PU paint-baking metalplate), which is 0.01 g/h.

(2) Among the single-layer materials made inTaiwan, the b group (weather board)presents the smallest moisture-permeable

amount at 0.007 g/h; next is the f group(FRP hollow board), at 0.012 g/h. The ggroup of gypsum board exhibits thebiggest moisture-permeable amount,which is 1.62 g/h.

(3) Among the multi-layer materials madein Taiwan, Item 15 (colour corrugatedsteel plate conventional steel bearingplate calcium silicate board) presentthe smallest moisture-permeable amount,which is 0.001 g/h; however, Item 20

(hollow cement board conventionalsteel bearing plate gypsum board) exhi-bits the poorest moisture permeabilityresistance, which is 0.023 g/h.

3.3 Solar heat gainThe results of the solar heat gain cooling

load are shown in Table 8. The higher thetotal heat transmission rate, the bigger thecooling load of the external skin solar heatgain. According to the results of the cooling

load for the external skin solar heat gain, thebigger the Q value the heavier the coolingload of the skin material.

(1) Among them, the l group presents thegreatest cooling load, represented by1020 W; next is the m group, which is1018.3 W; and the b group exhibits thesmallest cooling load, which is 0.23 W.

(2) Among the single-layer materials madein Taiwan, the b group exhibits thesmallest cooling load; next is the ggroup, which is 0.3 W; and the e grouppresents the greatest cooling load.

(3) In the multi-layer material sector, Item16 presents the greatest cooling load,represented by 940.1 W; next is Item 15,by 894.5 W and Item 13 exhibits thesmallest cooling load, which is 1.8 W.

3.4 DiscussionFrom the above, it is shown that superior

heat-insulating performance does not neces-sarily mean better moisture permeability

resistance. Moreover, the skin material thatpresents superior moisture permeability resis-tance does not always present a higher cool-ing load. For this reason, the appropriate skinmaterials should be selected by matching withthe climatic environment where the building islocated. If the design of the building shouldfocus on heat insulation, then the skin mate-rial with the superior heat-insulating capacityshall be selected. However, if the dampnessresistance is the main concern, then the skinmaterial with the higher moisture permeabil-ity resistance shall be selected.

Summing up, modules #22 can be recom-mended for the multi-layer material used inheat insulation. As for a material focusing onmoisture resistance, module #15 can be rec-ommended. For a material focusing on solarheat gain, module #13 can be suggested.

Table 9 presented an overall prioritysequence of the shin materials. Taking theheat-insulating capacity, for example, theoverseas material with the best heat-insulatingcapacity is k group; that having the bestheat-insulating capacity among the Taiwan-made single-layer materials is the h groupand that having the best heat-insulatingcapacity among the Taiwan-made multi-layer materials is Item 22. The above resultshave provided useful information for greenbuilding industry to choose the proper local

W-S Hou et al. 419


14/17

Table 8 Comparison of solar heat gain cooling load of skins materials

Material Type Heat resistance

Coefficient 1/kx

(mK/W)

L (m) Tsa (8C) Ti (8C) U (W/m2

/k) Q (W) Cost(USD/m2

)

a. 1/45 0.002 26.1 17.5 45 247.68 6.1

b. 1/0.03 0.002 29.8 17.7 0.03 0.232 31.7

c. 1/45 0.002 29.0 18.1 45 313.92 5.5

d. 1/0.8 0.050 27.4 25.3 0.8 1.075 84.8

e. 1/45 0.003 30.2 17.2 45 374.4 15.8

f. 1/0.04 0.005 34.3 19.9 0.04 0.369 48.5

g. 1/0.17 0.050 21.9 19.0 0.17 0.316 2.4

h. 1/0.17 0.030 26.9 12.3 0.17 1.588 4.1

i. 1/0.12 0.030 31.1 22.3 0.12 0.676 2.4

j. 1/90.04 0.05 31.5 22.5 90.04 518.63 5.8

k. 1/90.042 0.05 27.3 13.4 90.042 801.01 18.2-24.2

l. 1/90.038 0.05 28.2 10.5 90.038 1019.95 48.5-63.6

m. 1/90.4 0.05 28.6 11.0 90.4 1018.27 48.5-63.6

1. (a e d) 1/90.8 0.055 27.9 19.2 90.8 505.574 106.72. (a e g) 1/90.17 0.055 25.9 17.0 90.17 513.608 24.23. (a e h) 1/90.17 0.035 25.8 17.3 90.17 490.525 25.94. (a e i) 1/90.12 0.035 28.0 20.2 90.12 449.879 24.25. (a f g) 1/45.21 0.057 24.1 15.0 45.21 263.303 57.06. (a f h) 1/45.21 0.037 34.4 19.8 45.21 422.442 58.67. (a f i) 1/45.16 0.037 32.2 23.4 45.16 254.341 57.08. (b e g) 1/45.20 0.055 32.3 21.5 45.2 312.422 49.89. (b e h) 1/45.20 0.035 28.6 15.2 45.2 387.635 51.510. (b e i) 1/45.15 0.035 33.2 17.7 45.15 447.888 49.811. (b f g) 1/0.23 0.057 29.0 12.6 0.23 2.414 82.612. (b f h) 1/0.23 0.037 36.3 22.5 0.23 2.031 84.213. (b f i) 1/0.18 0.037 32.3 16.8 0.18 1.786 82.614. (c e g) 1/90.17 0.055 30.0 15.8 90.17 819.465 23.715. (c e h) 1/90.17 0.035 31.5 16.0 90.17 894.486 25.416. (c e i) 1/90.12 0.035 33.3 17.0 90.12 940.132 23.717. (c f g) 1/45.21 0.055 30.5 18.2 45.21 355.893 56.418. (c f h) 1/45.21 0.035 28.0 15.8 45.21 353 58.119. (c f i) 1/45.16 0.035 25.9 8.3 45.16 508.682 56.420. (d e g) 1/45.97 0.103 30.5 19.2 45.97 332.455 103.021. (d e h) 1/45.97 0.083 33.5 19.1 45.97 423.660 104.722. (d e i) 1/45.92 0.083 32.0 15.0 45.92 499.610 103.023. (d f g) 1/1.01 0.105 27.4 13.5 1.01 8.985 135.824. (d f h) 1/1.01 0.085 36.0 19.8 1.01 10.472 137.425. (d f i) 1/0.96 0.085 30.8 17.2 0.96 8.356 135.8

Table 9 Building comprehensive assessment of housing skin materials

Level Material type Insulation

ability

Skin material

solar heat gain

Moisture

permeability

Best materials Multi-layer materials Germany NO. k NO. j NO. l

Single-layer materials Taiwan NO. h NO. b NO. b

Multi-layer materials Taiwan NO. 22 NO. 13 NO. 15

Good materials Multi-layer materials Germany NO. j NO. m NO. k

Single-layer materials Taiwan NO. e NO. g NO. f

Multi-layer materials Taiwan NO. 15 NO. 15 NO. 1, 5, 19

Poor materials Multi-layer materials Germany NO. m NO. l NO. m

Single-layer materials Taiwan NO. g NO. e NO. g

Multi-layer materials Taiwan NO. 4 NO. 16 NO. 20



15/17

skin materials in order to reduce the CO2emissions caused by transportation.

4 Conclusions

In this study, several types of skin materialswere adopted to carry out the heat-insulationexperiment. When evaluating the heat-insu-lating performance of the buildings outerskin, the moisture permeability resistance ofthe material must also be considered inaddition to the materials solar heat gainand heat resistance. For this reason, the outerskin material should be selected to match withthe climate where the building is located.If the building design is focused on heatinsulation, then the skin material with thebest heat-insulating capacity shall be selected;if the design is focused on moisture resistance,then the skin material exhibiting highermoisture permeability resistance shouldbe selected. For a multi-layer material usedto isolate the heat, modules 22 should beselected. If the moisture resistance is the mainconcern, then module 15 should be selected.

However, by comparing both the efficiency

and cost of all the above building skinmaterials, where the heat-insulating perfor-mance is taken as the key design point,modules #15 (heat-insulating capacity is63.9%, prices is 25.4 United States dollar[USD]/m2) could become the most properselection. In particular, by considering thedecrement of CO2 emissions caused by trans-portation, again, the local material modules#15 will be the best selection for greenbuilding industry.

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an analysis of heat insulation efficiency of building outer skins used for green building

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