Thermal Insulation

Time allowance: 1 hour

Presentation CPD Points: 5 CPD Points

Post presentation online quiz: 5 CPD points

What is Thermal Insulation?

The term thermal insulation refers to materials used to reduce the rate of heat transfer, or the methods and processes used to

reduce heat transfer

Methods of thermal transmittance

Question….

Can anyone name the four methods of heat transfer?

Conduction

Convection

Radiation

Phase change

Mode of heat transfer

Modes Of Heat Transfer

1. Conduction The transfer of heat through a solid object

2. Convection The transfer of heat by conduction in a moving

medium, such as a fluid or gas e.g. water or air

3. Radiation The transfer of heat by electromagnetic radiation

i.e. light waves

4. Phase change The transfer of heat by the potential energy

associated with the heat of phase change, such as boiling, condensation, or freezing

Mode of heat transfer

Conductive Heat Transfer

Thermal conduction

Conduction occurs when heat travels through a medium

Conductive heat transfer is largely reduced by the presence of the air-filled spaces rather than by the material itself

Conductive barriers often have a layer or pockets of air to reduce heat transfer; an obvious example is double glazed windows

Convective Heat Transfer

Convective heat transfer occurs between two objects separated by a moving

interface of liquid or gas

Convective transfer

Convection can be reduced by dividing the convective medium into small compartments (or cells) to prevent large currents from forming

Convective currents, driven by heat energy, occur between the objects

The physical properties of the fluid or gas, and the speed at which the molecules travel, influence the rate of transfer

Radiative Heat Transfer

Most of the energy of the thermal radiation of objects (at room temperature) is in the infrared part of the spectrum

Thermal radiation

Thermal radiation is composed of all wavelengths of light

Any object above Absolute Zero (0 degrees K on the Kelvin scale, or −273.15° Celsius) radiates thermal radiation

Therefore, in thermal insulation the important consideration is the net direction of energy flow

Radiant barriers possess the characteristics of low emissivity, low absorptivity and high reflectivity in the infra-red spectrum

Thermal radiation continued

Therefore, only a small fraction of the radiant energy hitting the surface

is absorbed by such a material; most is being reflected back away and therefore there is little to re-emit

Question….

There are three main factors that compromise the performance of insulation;

what are they?

Moisture

Thermal bridging

Air

Moisture

Damp materials lose most of their insulating properties

Moisture

Similarly, if expanded polystyrene absorbs 5% moisture, it will halve its R value; this is particularly relevant in applications where itis in ‘in ground’ contact.

Therefore, the choice of insulation often dependson the ability to manage moisture and condensation on one side or the other of the insulator

Studies have shown that a 1% increase by volume of water in mineral fibre can increase heat loss by 105%

Thermal Bridging

Comparatively more heat flows through a path of least resistance than flows through an insulated path; this is known as a ‘thermal bridge’

Insulation around a bridge is of little help in preventing heat loss or gain through the bridge due to thermal bridging

Thermal bridging

This is often an issue where insulation is installed between structural members; the affect of this needs to be considered when calculating the ‘system R value’

Where thermal bridges make up 20% of the component area, the system R value for that component of the building may be reduced

by as much as 15%

Further, where the glazed area exceeds 30% of the wall area, the actual system R value may be as much as 40% less than the theoretical system R value

Thermal bridging

System versus Product R-values

Taken from the BRANZ Insulation Guide

Air Flow

Effective insulation relies on “still air”

Air flow

The result of this can be a reduction of the thermal performance of the insulation by up to 50%

A 2mm gap above and below an insulation panel can allow air circulation to occur around the insulation

This circulatory effect will eliminate the still air effect

Insulation Products

Foil Barriers

As discussed previously, aluminium foils are radiant heat insulators

Aluminium foils as radiant barriers

Being metal, foils are good conductors; therefore the effectiveness of an aluminium foil in preventing heat conduction, is minimal

This is particularly true if it abuts another material that also has a high thermal

conductivity, such as a purlins or portals

It also depends on the reflectivity the surface; if oxidization occurs the effectiveness as a radiant barrier is reduced

This is as a result of their low absorptivity and therefore their low emissivity

This has lead to the development of foil products with intermediary air pockets

These products seek to reduce the conductive potential of the foil and therefore increase the system R value

Radiant as combined barriers

When a radiant barrier faces an enclosed air space the combination of the foil

barrier and the still air gap form a conductive insulation barrier

This system has a measurable R-value

The size of the still air gap however largely determines the R value; the foil contributes very little on it’s own

Insulation Blankets

There are two main types of Building Insulation Blankets (B.I.B.s); glasswool, and polyester fibre.

Both glass and polyester blankets have similar thermal performance characteristics; they have a maximum service temperature of 120 degrees C.

At greater thicknesses and densities however, glass tends to perform better thermally

There are some advantages specific to glass over polyester such as the ability to drive mechanical fastenings through the material, particularly in roofing applications

Polyesters conversely tend to be more flexible and are less prone to collapse if they get wet

Insulation Blankets

We have seen a significant increase, in the last 5 years, of the specification of polyester insulation products. This is due to several factors:

Fibre migration within air-conditioning ducting and ventilated plenum spaces. This is despite the WHO removing the 2B (carcinogenic) classification and declaring it safe in October 2002

A perception that polyester insulation is greener than glass wool but…

Glass wool in fact contains around 80% recycled material

And uses 6,600 tonnes of waste window glass annually

Insulation Blankets

Polyester insulation, like glass wool, is a available in sheets and blanket form

Polyester is manufactured from a non–irritant, and non-combustible PET fibre

The recycled content of polyester insulation is increasing in particular via the use of old milk bottles

Efforts are also being made to reduce the embodied energy

However currently the raw materials for polyester insulation are shipped offshore, processed, and then shipped back to New

Zealand for manufacture into insulation

Currently, low density polyester insulation products contain at least 10% of recycled content, with high density products

containing up to 60%

Insulation Blankets

There is a small price premium for polyester over glass wool

In part due to the use of petroleum based product to manufacture polyester

Both are commonly installed in commercial applications, in conjunction with a foil and breathable vapour barrier, in roofs and walls

Common building practices have tended to compromise system R values

Recent legislative changes have meant a stricter enforcement of installation methods

This has impacted on install times and costs and led to the consideration of less traditional solutions

Insulation Blankets

Insulation Blankets

Traditional installation method

Required installation method

Rockwool Insulation

Rock or stone wool insulation

Rock wool, as the name suggests, is manufactured in a furnace from molten rock(typically basalt) at a temperature of about 1600 °C

Much as glass wool is manufactured, the molten rock is spun on high speed spinning wheels

It is a process similar to that used to make candyfloss

The final product is a mass of fine, intertwined fibres; an organic binder is added, often oil, to reduce dusting

Rockwool has a melting point of over 1000 degrees C, making it particularly suitable for fire protection

Question….

Rock or stone wool insulation

Metamorphic stones are good conductor of heat; why then are they used for insulation?

Though the individual fibres conduct heat very well, when pressed into rolls and sheets their ability to partition air makes them excellent heat insulators.

Their high density (between 40 and 120kg/m3) also makes them useful as an acoustic absorbers

Polystyrene Insulation

There are two types of polystyrene insulation:

Expanded or EPS polystyrene (density from 15 to 24kg/m3)

Extruded or XPS polystyrene (density 30kg and above)

Expanded polystyrene is an open cell product; it’s thermal performance is severely compromised when exposed to water and water vapour

Fact 2. Cell Structure Both foams are made using polystyrene monomer. This is the extent of their 'similarity' and the differences are self-evident upon close examination.

STYROFOAM* Extruded Closed Structure Fully closed cells. Water taken up only by direct absorption through polystyrene cell walls - very slow, if at all.

EPS (Expanded Polystyrene) Open Structure Part open, part closed cells. Interstitial voids allow water uptake. Size of voids can cause capillary action and water retention.

Fact 2. Cell Structure Both foams are made using polystyrene monomer. This is the extent of their 'similarity' and the differences are self-evident upon close examination.

STYROFOAM* Extruded Closed Structure Fully closed cells. Water taken up only by direct absorption through polystyrene cell walls - very slow, if at all.

EPS (Expanded Polystyrene) Open Structure Part open, part closed cells. Interstitial voids allow water uptake. Size of voids can cause capillary action and water retention.

Polystyrene Insulation

Extruded Polystyrene is a closed cell product which has minimal absorption characteristics

The thermal performance of extruded polystyrene is around 25% better than that of expanded polystyrene

Many extruded polystyrenes are blown with HCFC’s

These will be largely banned world wide by 2015

Some manufacturers, such as BASF, have therefore moved to CO2 blown manufacture of their expanded polystyrenes

The net result is an entrapment of an ozone depleting substance, rather than a release of it

With a CO2 blowing agent, rather than an HCFC however, there is a thermal performance loss of around 15%

This is due to the conductivity of the gases trapped within the cells and beads

Polystyrene Insulation

High Performance Insulation

High Performance Insulators

Legislative requirements and consumer demand has led to a significant increase

in legislated minimum R values

Key drivers for consumers are both a desire for ever larger glazed areas, and also the desire for more energy efficiency in their buildings

The desire for higher insulation values in walls and ceilings has always had to be

balanced against the impact on the building envelope; on the wall and ceiling thickness’ and the cost

High Performance Insulators

This has led to the development of high performance insulating materials such as Polyurethane (PUR), Polyisocyanurate (PIR) and Phenolic foams

These low density, rigid foam products deliver significantly higher thermal resistivity, for thickness, than more traditional insulants

Further, their closed cell structure means they do not provide a pathway for the ingress of moisture vapour into the insulating material, which significantly

reduces it’s thermal efficiency

Convective transfer - due to the fine closed cell structure of phenolic insulation products, heat transfer through convection is insignificant and can be ignored

High Performance Insulators

The performance of phenolic product can be explained by considering the four factors, which contribute to heat transfer:

Solid conduction – this factor is low in the phenolic cellular structure as the ‘solid content’ typically accounts for about 3-4% of the total volume ofthe low density insulation

Gaseous conduction - the blowing agents used in the creation of the

phenolic foam cellular structure, have very low thermal

conductivity compared to other gases and to air

Radiative transfer - due to their small cellular structure, phenolic foam has a comparatively low radiative heat transfer; radiative heat transfer increases with increasing cell diameter

All blown insulating products undergo changes in cell gas composition over time. This results in changes to their thermal conductivity

Many products, like Kingspan Kooltherm K10, are faced with gas-impermeable materials such as aluminium foil. These facings significantly reduce thermal conductivity aging caused bymigration of air into the insulation

Rigid phenolic insulation also out-performs all other types of rigid insulation for

fire performance. Alternatives such as polystyrene and polyurethanes are becoming less and less popular because of their flammability

Rigid phenolic insulation manufacturers subject their products to regulated testing. Quoted R values take into account aging and also include safety increments to ensure that products deliver better than specified performance over their life

European rigid phenolic insulation is CFC/HCFC-free and has zero ODP

High Performance Insulators

Insulation K values

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035

0.04

0.045

0.05

Rockwool Glass wool Polyester ExpandedPolystyrene

ExtrudedPolystyrene

Polyurethane Phenolic

K Value comparisons

U or K Value comparisons

Question….

I mentioned that Phenolic sheets have a solid content of 3-4%; glass wool is similarly only as little as 5% solid. Why do phenolics perform so much better thermally?

Closed cell structure

The very small size of the individual cells largely prevent radiative heat transfer

The gas contained within the cells is a poor thermal conductor

What role does the foil face play in the long term effectiveness of rigid phenolic insulation product?

It largely prevents the migration of air into the cells

As air is a better thermal conductor than the gas within the cells, it significantly improves the insulation’s long term

thermal performance

Cost versus performance

Thickness to achieve R2.6 versus cost m2

100

165

120

6055

$9.00$16.00

$25.00

$12.00

$25.00

$40.00$30.00

75

140

0

20

40

60

80

100

120

140

160

180

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Exp

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Extru

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Polye

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Rock W

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PU

R/P

IR

Phe

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(Ko

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Material

Th

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Thickness Cost/m2

Pipe insulation

Pipe insulation fulfils an important function in maintaining the operational reliability of industrial equipment

Insulation keeps the process running, ensures corrosion protection, reduces noise emissions and increases the energy efficiency of the installation

It should therefore be taken into adequate consideration at an early stage of planning

Pipe insulation is made in three forms:  

Open cell insulation

Closed cell rigid pipe sections

Closed cell flexible pipe sections

Open Cell Pipe Insulation

Manufactured as a pipe profile section, as a flexible blanket or as a semi rigid board

Densities vary across manufacturers but generally they are around 30-42 kg/m3

The blanket forms are wrapped around objects that are irregular in shape

Blankets are also used to clad large, flat areas

Blanket-type insulation can be specified to protect against heat loss, impact protection and/or fire

Open Cell Pipe Sections

For temperatures between 20 and 400 degrees C, glass fibre insulation is commonly used

This is often bonded to a foil facing to allow wrapping around tight radius and also to increase it insulative properties

For temperatures above around 400 degrees more specialist, high temperature insulators such as Rockwool and ceramic fibres,

such as Calcium Silicate, in rigid pipe sections and blankets are used

Where low temperatures, chemical attack and or moisture ingress (such as in in-ground applications) are a concern, a closed cell

rigid pipe section, such as FoamGlas, is recommended

Open Cell Pipe Sections

Question….

What are the three primary purposes for insulating pipe work?

1. To prevent heat loss

2. To prevent injury through contact 

3. Condensation control

Rigid Closed Cell Insulation

Rigid preformed sections are used primarily on straight pipe runs; to both insulate and protect

They are most commonly specified for their extremely high insulating properties, their impact resistance and their chemicalresistance

One such example is Foamglas pipe insulation

Foamglas is a lightweight, rigid, insulating material composed of millions of completely sealed glass cells; each an insulating space

Closed cell, rigid, preformed pipe sections

The all-glass, closed-cell structure makes it a very effective insulator (its U value is between 0.03 and 0.04)

It also has the capability to perform at operating temperatures from minus 268 to plus 482 degrees C

Foamglas is resistant to water in both liquid and vapour form; it is therefore well suited for use in buried and aggressive environments

It is also non-combustible and cannot absorb combustible liquids or vapours

It is also CFC and HCFC free

Closed cell, rigid, preformed pipe sections

Flexible Closed Cell Insulation

For pipe work which carry fluids at below ambient temperature, closed cell insulation should be used

This is because between 40 and 60 % of the maintenance costs for pipe work is due to corrosion under insulation

The main cause of corrosion is damp insulation

Moisture can penetrate the insulation due to damaged to the cladding and/or through water vapour transmission

Condensation occurs when the surface temperature of the pipe is below the dew point temperature

Or when it falls below the dew point temperature, due to changing operating temperatures

In these cases effective corrosion protection must be applied

Flexible Closed Cell Pipe Insulation

Low-temperature insulation materials should therefore be closed-cell

And have a high resistance to water vapour transmission

This is because the low-temperature insulation must prevent moisture from the ambient air penetrating the insulation material

As will occur with an open cell insulation such as glass wool or rock wool

This is known as institial condensation

Flexible Closed Cell Pipe Insulation

ROI case study

The energy saving potential which can be realized by insulating industrial equipment is immense

Calculations carried out by the Dutch Centre for Technical Insulation (NCTI) showed a refinery with a capacity of 300,000 barrels per day, could achieve annual savings of 66 million Euros by insulating 1,375 km of pipe work

According to the NCTI’s model calculation, the costs for the insulation would be paid off after just 3 months

Further, the CO2 emissions could be reduced by 500,000 tonnes a year

The PVC Nitrol pipe insulating products such as the Armaflex range from Armacell offer a thermal conductivity at l0°C ≤ 0.033 W/m.K

When Armaflex is used for pipe insulation on refrigerated lines, the simultaneous improvement of the thermal conductivity and resistance to water vapour transmission has a particularly positive effect on the long-term performance of the pipe work

Question….

What two properties might limit the use of polyesters in pipe insulation?

Maximum operating temperature (120 degrees)

Open cell structure; condensation issues

At what temperature is glass wool is also not suitable?

Above 450 degrees (such as on boilers and furnaces); rock wools are commonly used

Above 120 degrees high temperature binders are added

What rock is rock wool manufactured from?

Most commonly basalt rock

Solid Construction

Recent changes in the Building Act regarding required minimum system R values have had a significant effect on traditional methods of solid

construction

The increases in minimum R values mean that solid wall construction methodologies that were acceptable in the past may not now comply with current legislation

The key to the acceptability of lower R values insolid construction is linked to the ability to utilize the thermal mass of the wall

The standard requires that the thermal mass is accessible; therefore, if the interior walls are insulated, to achieve the required R value, the thermal mass is no longer accessible

Changes in solid construction legislation

High performance insulators, such as phenolics, can deliver a cost effective and efficient solution; minimizing the installation time and also the lost interior space

Green Building

Buildings and associated communities account for over 40% of the world’s greenhouse gas emissions

Specifying the right insulation will increase the building’s energy efficiency, improve the health and well-being of the occupants and reduces

greenhouse gas emissions

It is a low tech and inexpensive solutionthat will deliver a high economic and environmental payback

Energy consumption in buildings is growing faster than most other areas of use

Insulation alone can cut New Zealand’s greenhouse gas emissions by up to 5%

Green Building

Ballard Library in Seattle

The return on the investment in specifying high quality insulation can be measured in months rather than years

Many of the products offered by Forman have zero ozone depleting potential and most contain no CFC’s, or HCFC’s

Many are sourced from suppliers who have made tangible, independently certified,

commitments to pursue sustainable manufacturing practices

We are have a number of our products, including the Kingspan Kooltherm K10, with enhanced listings on the Green Build Website

We are committed to sustainable solutions and continue to expand this area of our offering

Forman and Green Building

Yale Sculpture Building and Gallery

Discover Centre at South Lake Union

Conclusion

Forman have been specifying, selling, distributing and installing insulation products for almost 95 years; so we know insulation!

The range of products we distribute stretches across all the areas discussed today.

Our product range includes the distribution of:

We are happy to assist and advise on the best product for your application

Any Questions?