1

BIG Energy Upgrade:

Environmental burden of insulation materials for whole

building performance evaluation

2

Authors

Dr Danielle Densley Tingley

Dr Abigail Hathway

Dr Buick Davison

Publication Date

December 2013

Publisher

University of Sheffield

Copyright © 2013 The University of Sheffield

All rights reserved. No part of this report may be reproduced, adapted, stored in a

retrieval system or transmitted by any means, including photocopying, recording or

other electronic or mechanical methods, without the prior written permission of the

publisher.

For permission request, please contact:

Dr Abigail Hathway

a.hathway@sheffield.ac.uk

Dr Abigail Hathway

Department of Civil and Structural Engineering

Sir Frederick Mappin Building

Mappin Street

Sheffield

S1 3JD

United Kingdom

3

BIG Energy Upgrade Environmental burden of insulation materials for

whole building performance evaluation

Dr Danielle Densley Tingley

Dr Abigail Hathway

Dr Buick Davison

4

Acknowledgements

This work has been undertaken by the University of Sheffield as a part of the Work-Package 1

of the BIG Energy Upgrade programme (aka Energy Innovation for Deprived Communities). The

BIG Energy Upgrade is a flagship £14.9 million programme, part financed by the European

Union Regional Development Fund (ERDF) through the Yorkshire and Humber ERDF

Programme 2007-13, addressing the priority needs of reduction in carbon emissions and

creation of jobs. To address the issues in an integrated approach, the University of Sheffield

has brought together a multidisciplinary team of academics who are working alongside Local

Authorities, ALMOs, social housing providers and an energy services company in delivering this

project.

We would like to thank the Local Authorities that have taken part and provided information for

this research, namely: Barnsley MBC, Doncaster MBC, Kirklees Council, Leeds City Council,

North Lincolnshire Council and North East Lincolnshire Council.

Our appreciation also goes to their Housing Partners (Berneslai Homes, Kirklees

Neighbourhood Housing, North Lincolnshire Homes, Shoreline Housing Partnership Ltd, St

Leger Homes, West North West Homes Leeds) and Management Partners (NPS Barnsley, Leeds

ALMO Business Centre) who have contributed to the University's work.

5

Executive Summary

This report assesses the whole life performance of external wall insulation systems which have

been installed to improve the thermal performance of the building fabric of hard to treat

homes. Work conducted includes the calculation of the environmental impacts of insulation,

estimation of payback periods and discussion of later life cycle stages.

The environmental impact of phenolic foam insulation boards, expanded polystyrene and

rockwool boards are quantified and compared. Expanded polystyrene has the lowest

environmental impact in the majority of the sixteen categories considered. A wider comparison

of embodied carbon also including woodfibre board and PIR boards found woodfibre board to

have the lowest embodied carbon by a significant margin – due to carbon sequestration within

the wood. The end of life stage was highlighted as an area requiring further work by the

industry to ensure that the render and adhesive layers can be separated from the insulation

boards once the systems are dismantled so that the insulation can be recycled rather than sent

to landfill or incinerated.

Briefing sheets (included as appendices) highlight key information about retrofitting British Iron

and Steel Federation (BISF) and Wimpey No Fines homes. Two briefing sheets summarise

information on phenolic foam boards and expanded polystyrene boards. A full report on

robustness testing can also be found in the appendices.

6

Contents

ACKNOWLEDGEMENTS 4

EXECUTIVE SUMMARY 5

1 INTRODUCTION 8

2 STATE OF THE ART 9

3 METHODOLOGY 10

3.1 ROBUSTNESS TESTING 10

3.2 LIFE CYCLE ASSESSMENT 10

4 RESULTS AND ANALYSIS 13

4.1 ROBUSTNESS TESTING 13

4.2 THE ENVIRONMENTAL IMPACTS OF PHENOLIC FOAM 14

4.3 ENVIRONMENTAL IMPACTS OF EXPANDED POLYSTYRENE INSULATION 18

4.4 INITIAL ENVIRONMENTAL IMPACT COMPARISON OF INSULATION MATERIALS 21

5 DISCUSSION 25

6 CONCLUSIONS 28

7 BEST PRACTICE GUIDANCE 30

8 REFERENCES 31

9 APPENDICES I

9.1 DRAWINGS OF RETROFIT MEASURES I 9.1.1 KIRKLEES BISF HOMES I 9.1.2 DONCASTER BISF HOMES II 9.1.3 INSULATION SYSTEMS TO SOLID WALL HOMES, E.G. L2, NL1 & NEL 1 III

9.2 BRIEFING SHEETS IV 9.2.1 BISF HOUSES IV-V 9.2.2 WIMPEY NO FINES HOUSES VI-VII 9.2.3 PHENOLIC FOAM INSULATION VIII-IX 9.2.4 EXPANDED POLYSTYRENE INSULATION X-XI

9.3 REPORT: ROBUSTNESS TESTING OF EXTERNAL WALL INSULATION SYSTEMS XII-XLI

7

List of Units

Unit Explanation

J Joule – unit of energy

KPa Measure of stress, force/area, Pa = N/m2

W/mK Measure of the thermal conductivity of a material, watts per meter kelvin

W/m2K Measure of thermal transmittance, watts per metre squared kelvin

kg CO2 eq Kg of carbon dioxide equivalents

kg CFC-11 eq Kg of CFC-11 (chlorofluorocarbon) equivalents

CTUh Comparative Toxic Unit - Human

kg PM2.5 eq Kg of fine particulate matter

kg U235 eq Kg of uranium equivalents

CTUe Comparative Toxic Unit - Ecosystems

kg NMVOC eq Kg of Non-methane volatile organic compounds equivalents

molc H+ eq Molecules of hydrogen positive ion (contains more protons than electrons) equivalents

molc N eq Molecules of nitrogen equivalents

kg P eq Kg of phosphorus equivalents

kg N eq Kg of nitrogen equivalents

CTUe Comparative Toxic Unit - ecosystems

kg C deficit Kg of carbon deficit

m3 water eq Volume of water equivalents

kg Sb eq Kg of antimony equivalents

8

1 Introduction

This report critically reviews and analyses building fabric retrofit measures that have been

installed as part of the BIG Energy Upgrade project, a programme which has retrofitted hard-

to-treat homes (i.e. those without cavity walls) throughout the Yorkshire and Humber region.

The work focuses on external wall insulation (Figure 1). Across the region this was the main

measure installed to improve the energy efficiency of the building fabric. A whole life cycle

assessment approach is taken to ensure a full picture of the environmental burdens and

possible savings are evaluated. The work therefore assesses the environmental impacts caused

by the manufacture of the insulation materials which are the main component of external wall

insulation systems. Once installed these materials should improve the thermal performance of

the building, thus reducing the heating requirement. Environmental paybacks of the insulation

are estimated for a range of internal comfort temperatures as the potential savings will vary

depending on the internal temperatures that are maintained.

Figure 1: External wall insulation system build up

In addition, material properties, installation procedures and in-use robustness are examined to

identify areas which might cause underperformance of the insulation systems. This includes

laboratory testing of a selection of both insulation materials and built up systems, the results

of which are summarised within this report; a full report of these tests is also available online

and in the appendices (Densley Tingley et al. 2013). A review of two system built houses,

Wimpey No Fines and British Iron and Steel Federation (BISF) houses, is also conducted and

can be found in the briefing sheets in the appendices. This is utilised in conjunction with post-

retrofit performance data to assess why particular house types might underperform.

Existing

Wall

9

The work outlined has culminated in a number of best practice recommendations, as

summarised in section 7. Homes retrofitted as part of the BIG Energy Upgrade project

(approximately 1120) form a small part of the retrofit challenge across the UK. Dwellings

account for 26% of carbon dioxide emissions (National Refurbishment Centre, 2012). Estimates

suggest (Communities and Local Government, 2010) that 5% of English dwellings utilise non-

traditional construction, which includes Wimpey No Fines homes and British Iron and Steel

Federation (BISF) houses. A further 19% have 9” thick solid masonry walls which will also need

additional insulation, either internally or externally. The work outlined in this report is therefore

potentially applicable to 24% of the housing stock in England, approximately five million

homes (Communities and Local Government, 2010). The unique, whole life cycle approach

taken by this project gives insights into the most effective insulation choices to minimise whole

life environmental impacts of external wall insulation. These insights, used in conjunction with

recommended practices for installation, should result in greater energy savings and reduced

environmental impacts from retrofit.

2 State of the art

Discussions around the environmental impact of insulation generally focus on the savings that

can be achieved in-use. There are, however, studies emerging (Schmidt et al. 2004; Ardente et

al. 2008; Intini & Kuhtz, 2011; Dowson et al. 2012; Zampori et al. 2013) that explore the initial

environmental impacts of insulation, predominantly those from manufacturing the insulation.

The availability of this environmental impact data is crucial in making an informed choice on

which insulation to use. When the scale of retrofit across the UK is considered, the requirement

for insulation is large and thus selecting a material with a minimal environmental impact can

provide significant savings at the installation stage before the in-use savings are realised.

There is full or partial environmental impact data available for a range of insulation materials,

(Schmidt et al. 2004; Ardente et al. 2008; Intini & Kuhtz, 2011; Dowson et al. 2012; Zampori et

al. 2013) but there are gaps in this data, particularly for insulation used as part of external wall

insulation systems. There is currently no transparent information available for phenolic foam

boards, a material that has been used to retrofit many of the Big Energy Upgrade homes. This

lack of information has prevented life cycle assessments and payback calculations in other

ERDF social housing retrofit projects (Narec, 2013). A key output of this report is therefore to

provide environmental impact estimates for phenolic foam insulation boards. Provision of this

information will allow environmental impact comparisons of different external wall insulation

choices and environmental payback estimates for this and future projects.

10

3 Methodology

This work evaluates whole building performance of retrofitted homes. It is split into two

sections. The main section involves estimating the environmental burden of insulation materials

and their environmental payback times. The other, initial section, explores potential reasons for

underperformance of the systems, including laboratory robustness testing. The methodology

and approach to these sections of work is outlined below.

3.1 Robustness testing

Robustness testing of both insulation samples (Woodfibre Board, Phenolic Foam and Expanded

Polystyrene) and external wall insulation systems was conducted. Full systems were subjected

to 10J impact tests based on ISO 7892:1988 and ETAG 004 (2008). The results were recorded

using a high speed camera, still photographs and measurements of maximum crack diameters

and thicknesses. The compressive resistance of insulation samples and built up systems was

also tested. Insulation samples were compressed until they reached a 10% deformation (i.e. the

sample is compressed by 10% of the initial thickness, e.g. 60mm sample compressed by 6mm

to 54mm). In addition, insulation and built up system samples were compressed to 50%

deformation. For further details on the robustness tests see Densley Tingley et al. (2013)1.

3.2 Life Cycle Assessment

Life cycle assessment (LCA) is a recognised method of estimating the environmental impacts

over the whole life cycle of a product, system or building. A representation of the life cycle of

insulation materials is shown in Figure 2. The benefits of insulation in use, principally reducing

heating requirements, are often discussed, however it is also important to consider the

environmental burden associated with the manufacture of the insulation, the transport of it,

installation, maintenance and finally impacts from disposal. Exploring the whole life cycle gives

a full environmental picture of the material and can assist in the decision making process when

comparing different insulation choices.

1 A full report on robustness testing can be found in the appendices to this report

11

Figure 2: Life cycle stages of insulation

This report quantifies the cradle to gate environmental impacts of several insulation materials:

phenolic foam, expanded polystyrene and rockwool. A cradle-to-gate study encompasses the

environmental impacts from manufacturing the insulation, the scope of which is shown in

Figure 3. The other areas of the life cycle are site specific e.g. transport distances of the

insulation from the manufacturer to the site and in-use savings which are also dependant on

occupant behaviour.

Figure 3: Cradle to gate environmental impacts

The environmental impacts are quantified across sixteen impact categories: climate change,

ozone depletion, human toxicity-cancer effects, human toxicity-non cancer effects, particulate

matter, ionizing radiation HH (human health), ionizing radiation E (ecosystems), photochemical

12

ozone formation, acidification, terrestrial eutrophication, freshwater eutrophication, marine

eutrophication, freshwater ecotoxicity, land use, water resource depletion, mineral, fossil and

renewable resource depletion. These are explained in Table 1. Assessing the impacts over a

range of categories gives a representative picture of the environmental burdens of a material.

These impact categories, with characterisation factors, are recommended in the International

reference Life Cycle Data system (ILCD) from the European Commission-Joint Research Centre

– Institute for Environment and Sustainability (JRC-IES, 2011) and so have been selected for

use, this should enable the results to be comparable with other studies.

Impact Category Unit Explanation

Climate Change kg CO2 eq

Greenhouse gases that cause climate change added up as CO2

equivalents; uses global warming potentials from the 2007 report from

the Intergovernmental Panel on Climate Change (IPCC) over 100 year

timeframe.

Ozone Depletion kg CFC-11 eq Ozone depletion potentials (ODPs) from the World Meteorological

Organisation used to convert gases to CFC-11 equivalent.

Human Toxicity,

cancer effects

CTUh Comparative Toxic Unit for humans used, includes outdoor inhalation,

ingestion of drinking water and indirect ingestion of toxins, e.g. those

that have built up in plants, animals and fish (Rosenbaum et al. 2011a).

Human Toxicity,

non-cancer effects

CTUh Comparative Toxic Unit for humans used, details as above.

Particulate Matter kg PM2.5 eq Intake fraction of fine particles estimated from emissions.

Ionizing Radiation,

Human Health

kg U235 eq Includes transfer of contamination to the environment and potential

exposure. Some uncertainty associated with the long half life of many

radioactive materials.

Ionizing Radiation,

Ecosystems (interim)

CTUe Comparative Toxic Unit for ecosystems used, current model focuses on

effects in freshwater. Interim category recommended by the ILCD as

characterization factors have yet to be outlined in a peer reviewed

publication.

Photochemical

ozone formation

kg NMVOC eq Emissions that cause increasing ozone concentration in the troposphere

are characterised to Non-Methane Volatile Organic Compounds eq. Low

level ozone can damage vegetation and cause impacts on human health.

Acidification molc H+ eq Based on accumulated exceedance, this includes atmospheric

transportation and deposition of emissions whilst accounting for

vulnerabilities of different ecosystems, for more details see Seppala et al.

(2006).

13

Terrestrial

Eutrophication2

molc N eq Based on accumulated exceedance, assessment of soil and atmospheric

conditions and accounts for sensitivities of biodiversity in different areas

(Seppala et al., 2006).

Freshwater

Eutrophication

kg P eq Estimates nutrient concentrations that have transferred to a freshwater

aquatic environment, focusing on phosphorous.

Marine

Eutrophication

kg N eq As above, but focuses on marine aquatic environments, assessing

nitrogen equivalent concentrations.

Freshwater

Ecotoxicity

CTUe Comparative Toxic Unit for ecosystems used, this accounts for exposure,

potential transport and effects on ecosystems (Henderson et al. 2011).

Land Use kg C deficit Assesses the quality deficit of the land occupied, using soil organic

matter as a quality indicator.

Water Resource

Depletion

m3 water eq Considers water use and relates this to local scarcity.

Mineral, fossil &

renewable resource

depletion

kg Sb eq Utilises abiotic (physical, non-biological resources) depletion potential, a

ratio between the annual resource extraction and the reserves available.

All resources converted to antimony equivalents.

Table 1: Environmental Impact Categories

The results will be shown in two ways (i) tabular quantified environmental impacts for each

category and (ii) comparison graphs. In the comparison graphs the material with the greatest

impact in a category is shown at 100% impact, the impact of the other materials are then

shown relative to this.

4 Results and Analysis

4.1 Robustness Testing

Compression and impact tests were conducted on three different insulation samples: phenolic

foam, EPS and woodfibre board. The results are summarised here; for the full report see

Densley Tingley et al. 2013. In the impact tests, across all three systems, the base rail detail

proved to be a weak point, with cracking occurring to the render around the point of impact

and along the base rail. This is an area of concern as repeated impacts to the area could cause

the base rail to detach from the system, which would allow significant water ingress, potentially

affecting the thermal conductivity of the systems. For the systems with a four board joint, (i.e.

phenolic foam and EPS) impact on the joint caused greater compression and cracking than

impacts to the centre of a panel. Additional reinforcement mesh at these joint locations might

2 Eutrophication refers to large supplies of nutrients (e.g. nitrogen and phosphorus) to an environmental

system which can cause excessive growth of plants and disrupt ecosystems. For more information on the

impacts of eutrophication see Smith et al. (1999).

14

improve the impact resistance. The tongue and groove jointing technique of the woodfibre

boards meant that when impacts occurred over a joint the system flexed and the force was

spread across the boards at the joint, reducing the potential permanent damage.

The woodfibre boards had the strongest 50% compressive resistance, then the phenolic foam,

then EPS. For 10% compressive resistance the order alters, with phenolic foam having the

highest, then woodfibre board, then EPS. This is due to the materials properties and the yield

points of the insulation. On application of applied stress, when the materials’ yield points are

reached permanent damage to the materials occurs. The yield points for the materials were

measured as follows, EPS 40KPa, phenolic foam 120KPa, and woodfibre 200KPa, above these

points permanent damage will occur. This level of stress, particularly 40KPa and 120KPa, could

occur to in-situ systems from projectiles or vandalism.

Permanent visible deformation was observed for the phenolic foam under 50% compressive

deformation and on closer examination voids were found within the closed cell structure,

suggesting that the thermal conductivity of the insulation might be compromised. In contrast,

there was no visible deformation to both the EPS and woodfibre samples; they displayed good

bounce back from the maximum level of deformation at 65% and 69% respectively, compared

to the phenolic foam at 37%. This correlated with the visible bounce back from the impact

tests as captured on a high speed camera.

These results indicate that if the external wall insulation systems are subjected to impacts,

permanent damage may be caused. Cracking may allow water ingress to the insulation and

this in combination with compression of the materials may affect the thermal conductivity of

the systems. It can therefore be concluded that if external wall insulation systems are found to

be underperforming they should be checked for impact damage, cracking and compression as

this could be a possible cause for underperformance; although the effects will likely be

confined to a localised area around the impact.

4.2 The Environmental Impacts of Phenolic Foam

Phenolic foam insulation is a commonly used external wall insulation material due to its low

thermal conductivity, 0.020W/mK, which means, for the same u-value, smaller thicknesses of

foam can be applied compared to other insulation materials. The foam has a closed cell

structure which resists moisture and water vapour ingress. It is manufactured from fossil fuel

derivatives, utilising phenolic resin as its main chemical component.

Due to the lack of available, transparent environmental data for phenolic foam insulation it was

necessary to conduct work to provide estimates across the environmental impact categories for

15

phenolic foam insulation boards. The estimates are based on the input chemicals as specified

in a recent patent (Kingspan Holding Ltd, 2006). The input chemicals and quantities are

summarised in Figure 4. Ecoinvent data from SimaPro 7 was used to estimate the

environmental impacts of the majority of the chemicals; although this was supplemented with

additional data (Schindler et al. 2010, ELCD 3.0, unknown date) where required. SimaPro 7, LCA

software, was used to conduct the environmental impact assessment.

Figure 4: Diagram showing the chemical inputs to make phenolic foam insulation

The contribution to the environmental impact of phenolic foam of each of the input chemicals

and key processes is shown in Figure 5. This demonstrates that phenolic resin accounts for the

majority of the environmental impact across the categories; this would be expected as it is the

main input chemical. The foaming and expanding process also makes a reasonable

contribution to all the categories. The input from the remaining chemicals varies significantly

depending on the impact category. For example, calcium carbonate has a minimal impact in all

categories except for ionising radiation E where it has a considerable impact compared to the

contribution from the other chemicals. This graph (Figure 5) only shows the relative impact of

each chemical to the overall impact of the phenolic foam not the significance of the impact of

each category. Table 2 displays the quantified impacts for each category for 1m2 of 60mm

thick phenolic foam insulation.

16

Figure 5: Breakdown showing the environmental impact from the components of phenolic

foam insulation

Phenolic foam has a reasonably high embodied carbon if compared to other materials,

however due to its recognised savings in this category in-use it is not of prime concern. Other

categories with high impacts include freshwater ecotoxicity and water resource depletion. If

environmental improvements were to be made, it is suggested that these categories be

targeted.

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100% %

Environmental Impact Categories

Foaming, expanding

Calcium Carbonate

Aromatic Polyester Polyol

Ethylene oxide

Urea

Phenolic resin

Acids mix

Blowing agent mix

17

Impact category Total Unit

Acidification 0.076 molc H+ eq

Climate change 17.06 kg CO2 eq

Freshwater ecotoxicity 36.03 CTUe

Freshwater eutrophication 0.0047 kg P eq

Human toxicity, cancer effects 7.32x10-7 CTUh

Human toxicity, non-cancer effects 6.74x10-7 CTUh

Ionizing radiation E (interim) 1.34x10-5 CTUe

Ionizing radiation HH 3.22 kg U235 eq

Land use 6.026 kg C deficit

Marine eutrophication 0.011 kg N eq

Mineral, fossil & ren resource depletion 4.84x10-5 kg Sb eq

Ozone depletion 7.15x10-7 kg CFC-11 eq

Particulate matter 0.0069 kg PM2.5 eq

Photochemical ozone formation 0.085 kg NMVOC eq

Terrestrial eutrophication 0.12 molc N eq

Water resource depletion 0.032 m3 water eq

Table 2: Environmental Impact of 1m2, 60mm (R=3m2K/W) phenolic foam insulation

The significance of the environmental impacts of phenolic foam insulation can perhaps be best

ascertained by looking at the environmental payback times from the savings accrued in-use.

Table 3 shows the environmental payback times for the environmental impacts of a terraced

house retrofit with phenolic foam insulation. The savings are based on the fall in gas use

resulting from the reduction in heat loss through the external walls after phenolic insulation is

installed. External temperatures are based on a Typical Temperature Year (Department of

Energy, 2012) and it is assumed that a constant internal temperature is maintained. The

payback times are shown for three different internal temperatures, 20°C, 18°C and 16°C. This

range of temperatures was used as monitored internal temperatures (within homes in the Big

Energy Upgrade project) were found with this level of variation.

18

Impact category Years Payback, 20°C Years Payback, 18°C Years Payback 16°C

Climate change 0.39 0.48 0.61

Ozone depletion 0.11 0.13 0.17

Human toxicity, cancer effects 1.66 2.03 2.59

Human toxicity, non-cancer effects 1.61 1.97 2.51

Particulate matter 3.10 3.79 4.82

Ionizing radiation HH 3.43 4.19 5.34

Ionizing radiation E (interim) 4.61 5.63 7.17

Photochemical ozone formation 2.02 2.47 3.14

Acidification 1.71 2.09 2.66

Terrestrial eutrophication 1.28 1.56 1.99

Freshwater eutrophication 3.28 4.00 5.09

Marine eutrophication 1.26 1.54 1.96

Freshwater ecotoxicity 6.43 7.86 10.00

Land use 0.25 0.30 0.38

Water resource depletion 11.30 13.81 17.57

Mineral, fossil & ren resource depletion 2.95 3.61 4.59

Table 3: Environmental payback time for initial embodied impacts of phenolic foam

From the environmental payback estimates it can be seen (Table 3) that there are two

categories in particular with long payback periods, freshwater ecotoxicity and water resource

depletion. The water resource depletion category is noteworthy, taking between 11-17.5 years

to pay back, which is in part due to gas having a low water impact and so the associated

savings will be small. However, the water demand in the manufacturing of phenolic foam is not

insubstantial. A total of 1.37m3 of water is required to produce the phenolic foam (43m2) to

retrofit the terraced house example. This amount of water equates to what the average person

would use over approximately 10 days. In contrast, the payback times for the climate change

category are short, within a year for all three scenarios.

4.3 Environmental Impacts of Expanded Polystyrene Insulation

Expanded polystyrene (EPS) is manufactured from closed cell plastic beads which are expanded

utilising a blowing agent, generally pentane (Hobbs & Ashford, 2012). The beads are fused

together in moulds to form rigid boards which are used within external wall insulation systems.

Environmental impact data from the Ecoinvent database (Ecoinvent Centre, 2013) was used to

quantify the burdens associated with the manufacture of 1m2, 114mm thick EPS, with a u-

value=0.33W/(m2K). The impacts are shown for each category in Table 4. These are calculated

for a thickness of insulation to specifically give a u-value=0.33W/(m2K) so that the results can

19

be compared to phenolic foam of the same u-value – this means that the in-use savings would

be kept constant. In reality, a specification of 110mm or 120mm of EPS would be required as it

is available in 10mm increments.

Impact category Total Unit

Acidification 0.060 molc H+ eq

Climate change 14.38 kg CO2 eq

Freshwater ecotoxicity 17.12 CTUe

Freshwater eutrophication 0.0016 kg P eq

Human toxicity, cancer effects 4.95x10-7 CTUh

Human toxicity, non-cancer effects 1.72x10-7 CTUh

Ionizing radiation E (interim) 3.60x10-6 CTUe

Ionizing radiation HH 1.16 kg U235 eq

Land use 1.69 kg C deficit

Marine eutrophication 0.0087 kg N eq

Mineral, fossil & ren resource depletion 1.29x10-5 kg Sb eq

Ozone depletion 4.51x10-7 kg CFC-11 eq

Particulate matter 0.0056 kg PM2.5 eq

Photochemical ozone formation 0.079 kg NMVOC eq

Terrestrial eutrophication 0.091 molc N eq

Water resource depletion 0.0056 m3 water eq

Table 4: Environmental impact of 1m2, 114mm thick, (R=3m2K/W) EPS

The environmental impacts of EPS can best be put into context by investigating the

environmental payback periods for each category. The methods utilised were identical to those

carried out for phenolic foam insulation. The payback time, in years, is shown in Table 5 for the

three different internal temperatures. The lower the internal temperature maintained the longer

the payback period as less gas is used to heat the property. It can be seen that all the

environmental impact categories pay back within five years. The two categories with the

longest payback periods are particulate matter and freshwater ecotoxicity. It is therefore these

categories that should be targeted for reduction if environmental improvements were to be

made to EPS insulation boards.

20

Impact category Years Payback 20°C Years Payback 18°C Years Payback 16°C

Climate change 0.32 0.39 0.50

Ozone depletion 0.07 0.08 0.10

Human toxicity, cancer effects 1.09 1.33 1.69

Human toxicity, non-cancer effects 0.40 0.49 0.62

Particulate matter 2.45 3.00 3.79

Ionizing radiation HH 1.20 1.46 1.85

Ionizing radiation E (interim) 1.20 1.47 1.86

Photochemical ozone formation 1.82 2.22 2.82

Acidification 1.31 1.61 2.03

Terrestrial eutrophication 0.91 1.12 1.41

Freshwater eutrophication 1.08 1.32 1.67

Marine eutrophication 0.93 1.14 1.44

Freshwater ecotoxicity 2.96 3.62 4.58

Land use 0.07 0.08 0.10

Water resource depletion 1.93 2.36 2.99

Mineral, fossil & ren resource depletion 0.76 0.93 1.18

Table 5: Payback times, in years, for EPS Insulation

One way in which to improve the environmental performance of EPS boards would be to use

recycled material within the feedstock. EPS can be recycled – either mechanically or chemically

(Hobbs & Ashford, 2012); although grinding the material down to be used as new bead

feedstock is the most common method. In addition, there is a growing framework of collection

points to enable EPS to be recycled (EPS, 2012). With EPS also used for disposable packaging

there is potentially a large feedstock of recyclable material.

A comparison has been made to investigate the environmental impacts of different recycled

contents of EPS. Three types are compared: typical EPS (0% recycled), 45% recycled EPS and

100% recycled EPS. The environmental impact comparison graph is shown in Figure 6. This

demonstrates that 45% recycled EPS has a lower environmental impact across the categories

than typical EPS. 100% recycled EPS has a lower impact than both options across all categories

except the ionising radiation categories where the 100% recycled content EPS has a higher

impact than the 45% recycled EPS – this may be due to the additional regrinding required for

100% recycled EPS. The comparison graph clearly demonstrates the environmental impact

benefits of utilising recycled EPS. However, there is currently no published data on what the

current recycled content, if any, of EPS insulation is. A first step in specifying EPS with a specific

recycled content is the availability of this information. Asking suppliers for the current recycled

21

content of EPS would improve the availability of this information and will thus facilitate the

specification of recycled EPS insulation in the future.

Figure 6: Environmental impact comparison of EPS with different recycled contents

4.4 Initial Environmental Impact Comparison of Insulation Materials

This section utilises environmental impact data discussed in previous sections to conduct an

environmental impact comparison of different external wall insulation materials. The

quantitative comparison covers the life cycle stages from cradle to gate, this includes the

extraction, processing and manufacture of the insulation materials. A discussion of the

environmental impacts of the other life cycle stages can be found in section 5. A full

environmental impact comparison across all sixteen categories is made for EPS, rockwool and

phenolic foam; the results can be seen in Table 7 and Figure 7. An expanded embodied carbon

comparison (Figure 8) is made with two additional materials, PIR (polyisocyanurate) insulation

and woodfibre board. The comparisons are conducted for insulation materials with the same u-

value, u=0.33W/(m2K), this means that in-use savings will be the same and the initial impacts

can be directly compared. The thermal conductivity and required insulation thickness for the

different materials can be found in Table 6.

0

10

20

30

40

50

60

70

80

90

100

%

Impact Category

100% recycled EPS

45% recycled EPS

Typical EPS

22

Insulation Material Thermal Conductivity

(W/mK)

Required Thickness for u-value

= 0.33W/(m2K)

EPS 0.038 114mm

Phenolic Foam 0.020 60mm

Rockwool 0.036 108mm

PIR Insulation 0.027 81mm

Woodfibre Board 0.044 132mm

Table 6: Properties of insulation materials

Comparing the difference thickness requirements of the insulation is a useful step as it may

give an indication of the suitability of the insulation for a specific project. For many projects

the thickness of insulation applied to the outside of a building will not be an issue. However,

for some projects there may be limited space, or difficulties with detailing around openings or

eaves if larger thicknesses of insulation are specified. Phenolic foam has the smallest thickness,

60mm, for a u-value=0.33W/(m2K) and woodfibre board the largest, at 132mm.

Impact category EPS Rockwool Phenolic Foam Unit

Climate change 14.38 15.52 17.06 kg CO2 eq

Ozone depletion 4.51x10-7 7.60x10-7 7.15x10-7 kg CFC-11 eq

Human toxicity, cancer effects 4.95x10-7 7.49x10-7 7.32x10-7 CTUh

Human toxicity, non-cancer effects 1.72x10-7 6.77x10-7 6.74x10-7 CTUh

Particulate matter 0.0056 0.014 0.0069 kg PM2.5 eq

Ionizing radiation HH 1.16 3.83 3.22 kg U235 eq

Ionizing radiation E (interim) 3.60x10-6 1.16x10-5 1.34x10-5 CTUe

Photochemical ozone formation 0.079 0.052 0.085 kg NMVOC eq

Acidification 0.060 0.14 0.076 molc H+ eq

Terrestrial eutrophication 0.091 0.26 0.12 molc N eq

Freshwater eutrophication 0.0016 0.0055 0.0047 kg P eq

Marine eutrophication 0.0087 0.015 0.011 kg N eq

Freshwater ecotoxicity 17.12 13.57 36.034 CTUe

Land use 1.69 12.90 6.026 kg C deficit

Water resource depletion 0.0056 0.023 0.032 m3 water eq

Mineral, fossil & ren resource depletion 1.29x10-5 4.79x10-5 4.84x10-5 kg Sb eq

Table 7: Environmental Impact comparison of EPS, Rockwool and phenolic foam

From Table 7 and Figure 7 it can be seen that EPS has the lowest environmental impact across

the categories with the exception of photochemical ozone formation and freshwater

ecotoxicity. Therefore, for the full impact comparison, EPS is the recommended insulation

choice to minimise the environmental impact of external wall insulation retrofit. Furthermore,

the EPS in the comparison has no recycled content; section 4.3 has shown that the

23

environmental impact could be reduced by introducing recycled material into the

manufacturing feedstock.

Rockwool has the greatest impact across ten of the impact categories, although for some

categories this is only by a marginal amount. Phenolic foam has the greatest impact in the

remaining six categories (climate change, ionising radiation E, photochemical ozone formation,

freshwater ecotoxicity, water depletion and mineral, fossil and renewable resource depletion).

Figure 7: Environmental impact comparison graph of EPS, Rockwool and phenolic foam

insulation

From the embodied carbon comparison in Figure 8 it can be seen that woodfibre board has

the lowest impact, -24.2 kgCO2eq, this is negative because the woodfibre board sequesters

carbon within it. Carbon dioxide is absorbed by trees for photosynthesis over their life time, by

removing this greenhouse gas from the air wood products are said to store carbon within

them, otherwise referred to as carbon sequestration. Woodfibre board is made from waste soft

wood, principally offcuts from sawmills and thus sequesters carbon within the boards (EPD-

PTX-2010121-D). The embodied carbon estimate for woodfibre boards accounts for

greenhouse gas emissions during the manufacture and for those associated with the transport

to the UK supply hub.

0

10

20

30

40

50

60

70

80

90

100

%

Environmental Impact Category

EPS

Rockwool

Phenolic Foam

24

The other four insulation options have embodied carbon values much closer together, (Figure

8), with the highest value for phenolic foam, 17.1 kgCO2eq, and the lowest for PIR, 12.8

kgCO2eq. EPS and rockwool fall in the middle of these two, with values of 13.9 kgCO2eq and

15.8 kgCO2eq respectively.

Figure 8: Embodied carbon comparison of external wall insulation materials.

*The embodied carbon for the woodfibre board insulation includes carbon sequestration and

transport for mainland Europe to a UK hub

The significance of the insulation choice can be best demonstrated by considering a whole

house retrofit and then scaling this up to large quantities of homes. The discussion shall focus

on two categories in particular, climate change and water resource depletion. The impacts of

these categories are easy to understand and climate change reduction is a key driver for the

retrofit of homes.

Utilising the terrace home example from earlier sections, where 43 m2 of insulation was

required, if EPS was used instead of phenolic foam, 115 kgCO2eq and 1.13 m3 of water eq

would be saved. Scaling this up to fifty terraced homes would result in savings of 5758

kgCO2eq and 57 m3 of water eq. Finally if 1000 homes (approximately the number that were

targeted for retrofit by the BEU project) were retrofitted with this alternative then 115,153

kgCO2eq and 1131 m3 of water eq would be saved. These savings are significant when

considered on this scale, if all UK homes were retrofitted using phenolic foam insulation then

there would be a very large water demand for the manufacture. The reduction is CO2eq is also

significant; this could be increased if woodfibre board was used as an alternative to EPS, in

-30.00

-25.00

-20.00

-15.00

-10.00

-5.00

0.00

5.00

10.00

15.00

20.00

Em

bo

die

d C

arb

on

(k

g C

O2e

q/m

2)

Insulation Materials

Phenolic Foam

EPS

RockWool

PIR

Woodfibre Board*

25

which case the overall balance would equate to one thousand tonnes of CO2eq being

sequestered within the insulation installed.

5 Discussion

The work so far has quantified the initial environmental impact of a number of external wall

insulation choices. This focused on the impacts from the manufacture of the insulation and

included consideration of in-use savings and payback times. The insulation choices will

however have further impacts throughout their life span, arising from transport, construction,

maintenance and disposal of the insulation.

All the insulation choices could either be sourced within the UK or in the case of woodfibre

boards have had transport to a UK hub included within the environmental impact estimate.

Impacts from transport to site will therefore be similar with all products transported by road

within the UK. There will be some variability in distances to site but this site specific and would

therefore need to be assessed as such.

The environmental impact of the construction process should be similar for all the insulation

choices. From discussions with contractors it was ascertained that the systems could be

installed onto a typical house with five days labour, one day to erect the scaffolding, three

days to install the insulation and a final day to remove the scaffolding. The process and

associated energy input are shown in Figure 9.

26

Figure 9: Construction process for installing external wall insulation

Maintenance to the systems should be minimal over their suggested thirty year life span (WBS,

2013). Minor damage should be removed by hand and patched but more extreme damage

would potentially require re-coating of the render system (WBS, unknown date). The

environmental impact associated to this will likely occur from on-site diesel usage to power a

generator and the environmental impact of the materials that require replacement. The

environmental impacts would be less than the original retrofit as application should be to a

localised area only. The required maintenance of the external wall systems in different areas

would need to be monitored to ascertain how likely and often a high level of maintenance is

required.

27

The most problematic issue at end of life for external wall insulation choices is contamination.

If the systems are removed from the house, they will be greatly damaged during the removal

process and reuse of them would not be an option. The insulation itself will have adhesives,

basecoats, mesh and render at least in part still attached to it; this means that the insulation is

considered contaminated which can present difficulties for recycling. Incineration with energy

recovery is a possibility for all the insulation options discussed although the chemicals released

during combustion may require capturing if harmful. End of life scenarios are also specific to a

particular insulation type.

It is suggested (Hobbs & Ashford, 2012) that landfill is the most common end of life route for

phenolic foam, although incineration is a possibility. Mechanical recycling could be possible if

the processes were developed, although waste flows might not be sufficient to support this

(Hobbs & Ashford, 2012). Contamination of demolition waste would likely be a problem for

recycling, so developing methods to separate the insulation boards from the render build up

would be a useful step; this could also be utilised for other insulation types.

EPS can be recycled at end of life and there are collection points across the UK (EPS, 2012)

that facilitate this. Although these can be limited for contaminated waste, there are several

sites that will take post-construction EPS if they are ‘reasonably clean and uncontaminated’

(Thompsett, 2012). The service is provided free of charge so if the majority of render and mesh

can be removed this option would be cheaper than sending the EPS to landfill. The recycling

that takes place is generally mechanical, breaking the EPS up, which is then used as the

feedstock for new products. Chemical recycling of the polymer is also technically possible

(Hobbs & Ashford, 2012). Another alternative at end of life is incineration with energy recovery,

EPS can be safely burnt and has a high calorific value, greater than that of coal (Hobbs &

Ashford, 2012), and so produces large quantities of heat when burnt, it may however produce

greenhouse gases when burnt.

Significant work is being conducted to explore the practicalities of recycling rockwool

insulation (WRAP, 2009; eco-innovation observatory, 2011, Rockwool Ltd. 2012). Practically

rockwool can be recycled and Rockwool Ltd. is aiming to increase the quantities recovered

from the waste stream. Work has largely focused on the feasibility of the collection of

rockwool waste because, just as for the other insulation types, contaminated material cannot

be recycled so this is a hurdle that must be overcome for external wall insulation systems,

otherwise contaminated rockwool will likely be landfilled.

28

The majority of PIR is currently sent to landfill, although incineration with energy recovery is a

viable alternative. Recycling is technically possible but not commonly practiced and will likely

lead to the production of alternative products (Hobbs & Ashford, 2012).

Woodfibre board, if untreated, can be recovered and reused again, however, this will not be

possible for those used in external wall insulation systems as the render build up will

contaminate the material. Contamination may also present a problem for recycling of the

material. However, contaminated recovered panels could be used for energy production in

incineration plants. In the EPD (EPD-PTX-2010121-D) it is stated that 91 kgCO2eq would be

produced during the disposal of 1m3 of woodfibre board; if the initial carbon impacts are also

considered the overall balance is -142 kgCO2eq, demonstrating that the woodfibre board

sequesters more carbon that is produced as a result of its manufacture and disposal.

The end of life stage is likely to have the most environmental impact of the life cycle stages

after manufacturing. In order to minimise the impacts at the end of life of the insulation and to

avoid the material being send to landfill, methods to separate the render system from the

insulation boards should be developed. If the contamination can be removed from the boards

then in some cases (EPS, rockwool and woodfibre) they can be recycled. In addition, the

technology and infrastructure may have been developed to recycle phenolic foam and PIR

once the systems installed now reach the end of their lives and require disposal.

6 Conclusions This report has examined the whole life cycle performance of external wall insulation systems.

There has been a focus on the environmental impact of insulation. By examining the

environmental impact of insulation materials over their whole life cycle a better understanding

of the materials can be gained and this information should be used when selecting insulation

materials.

The environmental impact of phenolic foam insulation has been quantified; this enables

insulation comparisons and the estimation of environmental paybacks in this and future

studies. The freshwater ecotoxicity and water resource depletion categories were found to have

the longest payback periods; these categories should be targeted for reduction if the

environmental impact of phenolic foam insulation is to be reduced.

EPS is another common external wall insulation choice, the environmental impact of this has

been investigated and it was found that the payback times for all categories were within five

years for the three internal temperature scenarios explored. A comparison was also made

29

between EPS with different recycled contents from which it was found that increasing the

recycled content reduces the environmental impact of EPS in all categories except for ionising

radiation where the 100% recycled EPS had a greater impact than the 45% EPS – this may be

due to the regrinding process. It is therefore recommended that EPS with a recycled content

be specified were possible and that manufacturers/suppliers are asked what the recycled

content is.

A full environmental impact comparison was conducted for phenolic foam, EPS and rockwool

insulation with the u-value of insulation choices kept constant at 0.33W/(m2K). The comparison

demonstrated that EPS had the lowest environmental impact across the majority of categories.

Rockwool has the highest impact in ten categories and phenolic foam in the remaining six. EPS

should therefore be the first choice of these three options in terms of minimising the

environmental impact of the retrofit. It is acknowledged that this is only one of many factors

within the decision making process but it should be considered.

The wider embodied carbon comparison included two other insulation materials, woodfibre

boards and PIR boards. Woodfibre boards had the lowest embodied carbon, a negative value,

-24.2 kgCO2eq, due to the carbon that is sequestered during the life of the trees that provide

the feedstock for the board. The other four insulation options are all synthetic and have similar

embodied carbon values, with variation between 12.8-17.1 kgCO2eq. Woodfibre board should

therefore be used if the minimisation of greenhouse gas emissions is the main priority.

The environmental impact of the remaining life cycle stages have also been discussed. The key

stage which has uncertainties is end of life. There are several disposal options for the different

insulation types, incineration with energy recovery is the most practical for contaminated

insulation. If methods can be developed to separate the external wall insulation layers, leaving

the insulation uncontaminated then current technologies allow EPS, rockwool and woodfibre

board to be recycled. Recycling of phenolic foam and PIR is technically feasible but not

currently practiced at scale; it may also result in alternative products to insulation board.

On an individual house scale the savings produced from an insulation choice may appear

small, but if considered on the scale of retrofit required across the UK the savings become

much more significant. Approximately one thousand homes were targeted for retrofit as part

of the Big Energy Upgrade. If one thousand terraced homes were retrofitted with EPS instead

of phenolic foam, 115 tonnes of CO2eq and 1131m3 of water would be saved. If the five million

homes that require thermal improvement were retrofitted with EPS instead of phenolic foam

then the savings would equate to 575,764 tonnes CO2eq and 5.6 million m3 of water. This is

from the retrofit alone; there will be further savings during the use of the material from the

30

reduction in heating requirement. When retrofitting homes to assist the UK in meeting

greenhouse gas reduction targets the use of a whole life cycle approach is crucial in order to

minimise environmental impacts across the life cycle.

7 Best Practice Guidance

The following list outlines key facts and recommendations found during the course of this

work, as outlined in this report and the briefing sheets found in the appendices. These

recommendations are designed for those selecting and specifying external wall insulation

systems.

1. Consider environmental impact as a key decision making factor when selecting external

wall insulation, utilising comparison graphs within this report

2. EPS has the lowest environmental impact across all but two impact categories

compared to phenolic foam and rockwool

3. Woodfibre board has the lowest embodied carbon of the five materials compared

4. Specify recycled EPS where possible and ask what the recycled content is

5. Woodfibre board has the highest 50% compressive resistance and is thus least

susceptible to impact damage (compared to phenolic foam and EPS)

6. Impact damage to the external wall insulation systems could be a factor if a home is

found to be underperforming

7. Air gaps between board joints could also be a factor in an underperforming home

8. Thermal bridging under the base of the external wall insulation system will be an area

of heat loss – possibly leading to underperformance of the home

9. For BISF houses integrate an air tightness strategy with the installation of external wall

insulation to improve overall thermal performance

10. For Wimpey No Fines homes if gable wall is brick clad this should be insulated too in

order to reduce thermal bridging

31

8 References

Ardente, F., Beccali, M., Cellura, M. & Mistretta, M. 2008. Building energy performance: a LCA

case study of kenaf-fibres insulation board. Energy and Buildings, 40, pp: 1-10

Communities and Local Government, 2010. English Housing Survey – Housing stock report

2008. Department for Communities and Local Government Publications: London. Available at:

https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/6703/1750754.p

df [accessed 06/11/13]

Densley Tingley, D., Stocks, G., Hathway, A., Allwood, D. & Davison, B. 2013. Robustness testing

of external wall insulation systems. Available in the appendices

Department of Energy, 2012. EnergyPlus Energy Simulation Software, Weather Data, All

Regions, United Kingdom. Available at:

http://apps1.eere.energy.gov/buildings/energyplus/cfm/weather_data3.cfm/region=6_europe_w

mo_region_6/country=GBR/cname=United%20Kingdom [accessed 03/12/13]

Dowson, M., Grogan, M., Birks, T., Harrison, D. & Craig, S. 2012. Streamlined life cycle

assessment of transparent silica aerogel made by supercritical drying. Applied Energy, 97, pp:

396-404

Eco-innovation observatory. Recycling of Used Rockwool. Available at: http://www.eco-

innovation.eu/index.php?option=com_content&view=article&id=406:recycling-of-used-

rockwool&catid=55:denmark [accessed 27/11/13]

Ecoinvent Centre. 2013. The ecoinvent Database. Available at:

http://www.ecoinvent.org/database/ [accessed 25/11/13]

ELCD 3.0 – European reference Life Cycle Database, Unknown date. Calcium Carbonate.

Available at: http://elcd.jrc.ec.europa.eu/ELCD3/resource/processes/6006d87e-ccee-42b1-b203-

f67c7c0bad97?format=html&version=03.00.000 [accessed 25/09/13]

EPD-PTX-2010121-D. Environmental product declaration: Pavatex Woodfibre insulation board.

Institut Bauen und Umwelt e. V.

EPS, 2012. EPS and the environment – find an EPS recycler. Available at:

http://www.eps.co.uk/sustainability/eps_recycler.html [accessed 25/11/13]

32

Hammond, G. & Jones, C. 2011. Inventory of Carbon & Energy (ICE) Version 2.0. Available at:

http://www.siegelstrain.com/site/pdf/ICE-v2.0-summary-tables.pdf [accessed 05/12/13]

Henderson, A.D., Hauschild, M.Z., van de Meent, D., Huijbregts, M.A.J., Larsen, H.F., Margni, N.,

McKone, T.E., Payet, J., Rosenbaum, R.K. & Jolliet, O. 2011. USEtox fate and ecotoxicity factors

for comparative assessment of toxic emissions in life cycle analysis: sensitivity to key chemical

properties. International Journal of Life Cycle Assessment, 16, pp:701-709

Hobbs, J. & Ashford, P. 2012. Building Insulation Foam Resource Efficiency Action Plan,

prepared by the Resource Efficiency Partnership. Available at:

http://www.wrap.org.uk/content/building-insulation-foam-resource-efficency-action-plan

[accessed 25/11/13]

Intini, F. & Kuhtz, S. 2011. Recycling in buildings: an LCA case study of a thermal insulation

panel made of polyester fibre, recycled from post-consumer PET bottles. International Journal

of LCA, 16, pp: 306-315

JRC-IES. 2011. ILCD Handbook, International Reference Life Cycle Data System,

Recommendations for Life Cycle Impact Assessment in the European context – based on

existing environmental impact assessment models and factors. Luxemburg: Publication Office of

the European Union.

Kingspan Holdings Limited. 2006. A Phenolic Foam. International Patent Application, No.

PCT/IC2006/000096, 8th September

Narec. 2013. ERDF Social Housing Energy Management Project, Final Project Report, October

2013. Available at: http://www.narec.co.uk/narec.co.uk/documents/erdf-social-

housing/erdf_social_housing_energy_management_-_final_project_report.pdf [accessed

28/11/13]

National Refurbishment Centre, 2012. Refurbishing the Nation – Gathering the evidence. BRE &

Energy Saving Trust. Available at:

http://www.rethinkingrefurbishment.com/filelibrary/nrc_pdf/NRC_reportSEP2012web.pdf

[accessed 06/11/13]

Rockwool Ltd. 2012. Recycling and waste Handling. Available at:

http://www.rockwool.com/csr/committed+to+society/sustainability+reports/recycling+and+wast

e+handling [accessed 27/11/13]

33

Rosenbaum, R.K., Huijbregts, M.A.J., Henderson, A.D., Margni, M., McKone, T.E., van de Meent,

D. Hauschild, M.Z., Shaked, S., Li, D.,S., Gold, L.S. & Jolliet, O. 2011. USEtox human exposure

and toxicity factors for comparative assessment of toxic emissions in life cycle analysis:

sensitivity to key chemical properties. International Journal of Life Cycle Assessment, 16, pp:

710-727

Schindler, A., Habel, F., & Baitz, M. PE International. March 2010. Eco-profile of Aromatic

Polyester Polyols (APP). Report for PU Europe, Federation of European rigid Polyurethane Foam

Associations. Available at: http://www.pu-europe.eu/site/fileadmin/Reports_public/PU_10-

204_PU_Europe_project_-_Eco-Profile_of_Aromatic_Polyester_Polyols__APP_.pdf [accessed

25/09/13]

Schmidt, A.C., Jensen, A.A., Clausen, A.U., Kamstrup, O. & Postlethwaite, D. 2004. A comparative

life cycle assessment of building insulation products made of stone wool, paper wool and flax,

part 2L comparative assessment. International Journal of LCA, 9 (2), pp:122-129

Seppala, J., Posch, M., Johansson, M. & Hettelingh, J.P. 2006. Country-Dependent

Characterisation Factors for Acidification and Terrestrial Eutrophication Based on Accumulated

Exceedance as an Impact Category Indicator. International Journal of LCA, 6, pp: 403-416

WBS (Wetherby Building Systems Ltd.) unknown date. Silicone & Acrylic, Aftercare &

Maintenance. Available at: http://www.wbs-ltd.co.uk/wp-

content/uploads/2011/10/silicone_aftercare.pdf [accessed 27/11/13]

WBS (Wetherby Building Systems Ltd.) 2013. System Approvals. Available at: http://www.wbs-

ltd.co.uk/wetherby-systems/system-approvals/ [accessed 27/11/13]

WRAP, 2009. Rockwool and Knapzak Trial, Deomstruaction trial report assessing the use of the

Knapzak container on site to collect waste mineral wool insulation for recycling by Rockwool

Ltd. Available at:

http://www.wrap.org.uk/sites/files/wrap/WRAP_Trial_Report_ROCKWOOL%2BKNAPZAK%20%282

%29.pdf [accessed 27/11/13]

Zampori, L., Dotelli, G. & Vernelli, V. 2013. Life cycle assessment of hemp cultivation and use of

hemp-based thermal insulator materials in buildings. Environmental Science Technology, 47,

pp: 7413-7420

i

9 Appendices

9.1 Drawings of Retrofit Measures

9.1.1 Kirklees BISF Homes

Existing finishes are retained unless corroded or damaged. Different retrofit treatments are

applied to the ground and first floor, as shown on the diagrams.

Existing Wall

EPS

Filler

60mm Phenolic

foam

Render

finish

Glass fibre

reinforcing mesh

Scrim

adhesive

ii

9.1.2 Doncaster BISF Homes

Existing

Wall

Render

finish

Glass fibre

reinforcing

mesh

Scrim

adhesive

60mm Phenolic

foam

18mm

plywood sheet

50mm timber

studs

Existing

Wall

Render

finish

Base coat Structherm system: EPS

insulation core with welded wire

cage surround

iii

9.1.3 Insulation systems to solid wall homes, e.g. L2, NL1 & NEL 1

9.2 Briefing Sheets

9.2.1 BISF Houses

9.2.2 Wimpey No Fines Houses

9.2.3 Phenolic Foam Insulation

9.2.4 Expanded Polystyrene Insulation

9.3 Report: Robustness testing of external wall insulation systems

iv

v

vi

vii

viii

ix

x

xi

xii

Robustness testing of external wall insulation systems

xiii

Authors

Dr Danielle Densley Tingley

Georgina Stocks

Dr Abigail Hathway

Dr Dan Allwood

Dr Buick Davison

Publication Date

November 2013

Publisher

University of Sheffield

Copyright © 2013 The University of Sheffield

All rights reserved. No part of this report may be reproduced, adapted, stored in a

retrieval system or transmitted by any means, including photocopying, recording, or

other electronic or mechanical methods without the prior written permission of the

publisher.

For permission request, please contact:

Dr Abigail Hathway

a.hathway@sheffield.ac.uk

Dr Abigail Hathway

Department of Civil and Structural Engineering

Sir Frederick Mappin Building

Mappin Street

Sheffield

S1 3JD

United Kingdom

xiv

Robustness Testing of External Wall Insulation Systems

Dr Danielle Densley Tingley

Georgina Stocks

Dr Abigail Hathway

Dr Dan Allwood

Dr Buick Davison

xv

Acknowledgements

We would like to thank Natural Building Technologies and other suppliers for kindly providing

us with external wall insulation samples to test; the work could not have been conducted

without these and their support is very much appreciated.

The project would not have been possible without funding as part of the University of

Sheffield’s SURE scheme, which funded the laboratory tests and our undergraduate student’s

time.

xvi

Contents

ACKNOWLEDGEMENTS XV

1 INTRODUCTION XVIII

2 HARD BODY IMPACT TESTS XIX

3 COMPRESSION TESTS XXVII

4 KEY FINDINGS AND RECOMMENDATIONS XXXII

5 REFERENCES XXXIV

6 APPENDIX XXXV

6.1 SUPPORTING INFORMATION FOR COMPRESSION TESTS XXXV 6.1.1 WOODFIBRE BOARD SAMPLES XXXV 6.1.2 EPS SAMPLES XXXVII 6.1.3 PHENOLIC FOAM SAMPLES XXXIX

xvii

Executive Summary

This report presents the results from laboratory-based robustness testing of external wall

insulation systems. Two tests were conducted: impact tests and compression tests. These were

carried out on three different insulation systems: woodfibre board, expanded polystyrene

boards and phenolic foam boards.

In both impact and compression tests the woodfibre samples showed good bounce back (high

elasticity) and low relative deformation. The jointing system utilised meant that on impact

across two or more boards the woodfibre performed as a system, spreading impact across a

larger area, reducing the permanent damage. High stresses (>1000KPa) were required to

achieve a 50% deformation of the samples, making it unlikely that high levels of permanent

deformation would occur to installed systems.

The phenolic foam samples required the highest stresses to reach a 10% deformation.

However, under the higher stresses (>300KPa) that cause a 50% deformation, permanent

deformation occurs to the cellular structure of the foam, which will be detrimental to its

thermal performance. It is a possibility that this level of force could occur to installed products,

through vandalism or hard body impacts.

The EPS samples suffered the greatest initial deformation across the impact tests, although

demonstrate good bounce back and low relative deformation. An area of concern for this

system is the level of cracking that occurs to the render upon impact. There is significant

compression of the insulation on impact, which cracks the render system. This could perhaps

be reduced if a render system with more flexibility was used, so it could bounce back after

compression with less permanent damage. Due to the low level of stress required (>170KPa), it

is likely that some compression and cracking to this in-situ system would occur if it is

subjected to even modest impacts.

To improve the robustness of the systems, it is recommended that developments are made to

two areas:

The base rail detail of all systems – cracking and metal deformation occurred here in the

impact tests of all three insulation systems. This would result in water ingress through the

render to the insulation, compromising the performance of the system.

The jointing between four boards for the phenolic foam and expanded polystyrene

systems – significant cracking was seen in the impact tests for four board join samples. As

above, this would allow water ingress into the systems.

xviii

1 Introduction

The aim of this work was to investigate the robustness of external wall insulation systems. As

these systems encase the outside of a house it is important that they can resist impacts from

projectiles, skateboards, vandalism and stand up to everyday life (e.g. ladders and bikes may

be leant against them) without significant damage. A series of laboratory tests have been

conducted to investigate the robustness of external wall insulation systems.

External wall insulation is applied to buildings, usually those with a solid wall, to improve their

thermal performance, thus lowering heating requirements and bills, and reducing the

environmental impacts associated with heating. These systems are built up of several layers

(Figure 10) fixed onto the existing wall mechanically and/or with adhesives. Damage will most

likely occur to the outer, rendered layer in the form of cracking. However, significant damage

could allow water penetration into the system, and this in turn may affect the thermal

conductivity of the insulation. Significant compression to the system could also affect the

thermal conductivity. It is therefore important to understand the likelihood of cracking and

compression to the systems.

Figure 10: External Wall Insulation System - Layer Build up

Three different insulation systems were investigated, a woodfibre board system, a phenolic

foam system and an expanded polystyrene (EPS) system. The specification of these and system

breakdowns can be seen in Table 8.

Existing Wall

xix

Woodfibre Board

System 3

Phenolic Foam System EPS System2

Diffutherm: 100mm thick

impact samples

60mm thick compression

samples

50mm thick Phenolic foam

board for all tests

50mm thick EPS board for all

tests

8mm MC55 –

multicontact bonding

mortar

Primer, Basecoat & Scrim Primer, Basecoat & Scrim

2mm Nanopor Putz Top

Coat

1.5mm Silicone Finish 1.5mm Silicone Finish

Table 8: System specification and components of testing samples

The systems were subjected to two tests: hard body impact tests and compression tests. The

procedure and results of these are outlined in sections 2 and 3.

2 Hard Body Impact Tests

All the hard body impact tests were conducted on built up system, rendered, insulation panels.

For each insulation type, four different samples were tested: a single panel, a joint between

two boards, a joint between four boards (three in the case of woodfibre due to the system

utilised) a base-rail detail, and an edge detail for the EPS and phenolic foam systems. More

details of these can be seen in Figure 11. Details of where the systems were impacted are also

shown in Figure 11, with up to three impacts per sample, each on a different area of the

sample.

3 Supplied by Natural Building Technologies, http://www.natural-building.co.uk/

xx

Figure 11: External wall insulation sample types tested. The ‘X’ marks indicate where the

samples were impacted (grey X marks are tests conducted on phenolic and EPS samples only).

The jointing technique between panels varied across the three systems, as shown in Figure 12.

The woodfibre boards lock closely together with little air gap between them, whereas a small

air gap can be seen between the phenolic foam and EPS boards.

Figure 12: Jointing between two insulation panels, (a) woodfibre board, (b) phenolic foam

board, (c) EPS insulation board

(b) (c) (a)

Phenolic & EPS

samples only tested

for four-board join

Woodfibre board

tests on three-

board join

Base rail detail

Edge detail,

phenolic & EPS

samples only

xxi

Each of the boards was subjected to a 10J impact. A 1 kg steel ball was dropped from a height

of 1.02m to the centre point of impact. A release point was marked on the red frame shown in

Figure 13 to ensure the drop height remained consistent. This test set up was based on ISO

7892:1988 and ETAG 004 (2008). Each of the samples was attached to a metal frame (Figure

13); the point of impact was always against the centre steel section piece to mimic the stiffness

of a wall. This was kept consistent throughout the tests. Videos of the impacts were taken

using a high-speed camera operated at a frame rate of 900 frames per second. Photographs of

the impacted surfaces were also taken and crack thicknesses recorded (Figure 14, Figure 15,

Figure 16, Table 9, Table 10, Table 11).

Figure 13: Photograph of the test set up for the impact tests, a mark on the red frame was

used as a release point for the pendulum, to ensure consistency. The high speed camera which

was used to capture the impacts can be seen in the bottom right corner.

The results for the woodfibre impact tests can be seen in Table 9. Cracking was typically in a

circular shape, as can be seen in Figure 14. In Table 9, the Dia. X is the widest diameter the

crack extended in the horizontal direction and Dia. Y refers to it in the vertical direction, the

greatest crack thickness is also given.

xxii

Woodfibre Centre Woodfibre two-board Woodfibre Base Rail Woodfibre

three-board

C T B A R M L A R M L A R L A

Dia. X (mm) 38 35 50 41 38 39 42 39.7 50 49 76 58.3 67 43 55

Dia. Y (mm) 44 29 38 37 40 40 45 41.7 19 23 24 22 53 39 46

Max. crack

thickness (mm)

0.3 0.1 0.3 0.23 0.4 0.1 0.1 0.2 0.6 0.2 0.3 0.37 0.5 0.6 0.55

Base rail damage

length (mm)

165 165 170 167

Table 9: Crack sizes for woodfibre board impact tests (Note that A refers to the average size

crack, the following notations indicate the position of impact on the board, R right, M middle,

L left, C centre, T top and B bottom)

Comparing the crack sizes for the different woodfibre samples, it can be seen that the greatest

crack thickness occurs for the three-board join, although the average diameter of this impact

was no larger than that from other tests. The base rail sees the widest crack in a horizontal

direction; the impact results in cracks along the base rail on average 167mm in length. From

the high-speed camera footage of the three-board join it can be seen that the whole

woodfibre board flexes on impact. This is seen to be particularly the case where two or three

boards join together. This dissipates the force, reducing the localised compression. The

material also visibly bounces back from the maximum compression point. The jointing system

of the woodfibre boards appears to facilitate this unified behaviour so that it acts more as a

system than an individual board.

xxiii

Figure 14: Typical impact behaviour of the woodfibre boards, (a) a single board; (b) two-board

join; (c) three-board join; (d) base rail impact

The impact results for phenolic foam can be seen in Table 10 and the typical cracking

behaviour in Figure 15. The crack thickness and diameter increased the more boards that are

joined, suggesting that the junction point between four boards is one of the weakest parts of

the system. However, the likelihood of impacts occurring to this specific junction is small. The

corner detail when impacted on a straight face performs well, although this might change if

impacts were incurred directly to the edge; further testing would be required to ascertain this.

The base rail damage, as with the woodfibre system, extends beyond the impact diameter, with

a crack forming along the metal base rail fixture (Figure 15). This result implies that repeated

impacts to this area would likely cause extensive damage and might result in the base rail

detail becoming detached from the system. More testing would be required to conclusively

ascertain the extent of damage that multiple impacts would cause. The high-speed camera

footage of the four board join showed that there is a small amount of flex from the whole

board upon impact, but the compression is significant and localised to the point of impact.

There is some bounce back but a visible impression remains in the surface of the sample.

(a) (b)

(c) (d)

xxiv

Phenolic Single Phenolic two-board Phenolic Base Rail Phenolic

Corner

Phenolic

four-

board

C T B A R M L A R M L A L M R

Dia. X (mm) 40 41 40 40.3 35 40 33 36 163 63 40 88.6 0 27 183 50

Dia. Y

(mm)

33 45 38 38.7 35 37 34 35.3 22 23 24 23 0 17 42 50

Max. crack

thickness (mm)

0.06 0.12 0.08 0.09 0.08 0.14 0.12 0.1 0.12 0.1 0.5 0.24 0 15 0.08 0.4

Base rail damage

length (mm)

284

Table 10: Crack sizes for phenolic foam impact tests (Note that A refers to the average size

crack, the following notations indicate the position of impact on the board, R right, M middle,

L left, C centre, T top and B bottom)

Figure 15: Impact test result for phenolic foam samples, (a) single board, (b) two-board join, (c)

four-board join, (d) base rail impact

(a) (b) (c)

(d)

xxv

The impact results for EPS can seen in Table 11 and Figure 16. The results show a similar

pattern to those of the phenolic foam, the crack thickness increases the more boards that join

together, although the crack thickness for EPS are larger than those for phenolic foam. The

impacts to the corner face cause minimal damage, with no visible cracking on two impacts and

a fine crack on the third. The base rail impacts show a similar pattern to the other samples,

with cracking along the rail and some deflection of the metal. From the high speed camera

image of the four board join it can be seen that there is significant compression to the sample

on impact. There is substantial bounce back seen, but the initial compression is such that large

cracks are formed in the render, with pieces breaking off.

EPS Centre EPS two-board EPS Base Rail EPS Corner EPS four-

board

C T B A R M L A R M L A L M R

Dia. X (mm) 45 61 31 45.7 58 46 49 51 71 45 59 58.3 0 0 110 64

Dia. Y (mm) 52 65 38 51.7 45 40 48 44.3 28 22 25 25 0 0 45 55

Max. crack

thickness (mm)

0.5 0.4 0.06 0.32 0.2 0.14 3 1.1 0.3 0.3 0.2 0.27 0 0 0.06 1.6

Base rail damage 160 117 107 128

Table 11: Crack sizes for EPS impact tests (Note that A refers to the average size crack, the

following notations indicate the position of impact on the board, R right, M middle, L left, C

centre, T top and B bottom)

(a) (b) (c)

xxvi

Figure 16: Impact test results for EPS boards, (a) Single board, (b) 2 board join, (c) 4 board join,

(d) base rail

The woodfibre board systems tested had a greater thickness of insulation, 100mm, compared

to the 50mm phenolic and EPS systems so the tests are not directly comparable. However, the

material behaviour on impact would likely be similar with different thicknesses of insulation.

Across the systems the base rail seems to be a weak point, with cracking occurring along it

upon impact. If this were subjected to multiple impacts the damage could become more

extensive. Multiple impacts are possible as this detail is close to the ground, so could be

kicked or have footballs kicked against it. Exploring means of strengthening this detail in all

systems is recommended.

Generally for the phenolic and EPS systems the base rail detail occurs 100mm off the ground,

leaving a cold bridge from the end of the insulation to the ground, as seen in Figure 17.

Detailing to avoid this cold bridge should be investigated in conjunction with improving the

impact resistance.

(d)

xxvii

Figure 17: Thermal image of home with external wall insulation

3 Compression Tests

Small samples of 60mm thick woodfibre board insulation (80x90mm laterally) and 50mm thick

EPS and phenolic foam (70x70mm laterally) were placed under compressive loads. Both the

built up insulation systems and isolated insulation samples, without render, were tested. Before

each test the exact size of the sample was measured; this size was measured again

immediately after compression, 1 hour after the compression test and 24 hours later. The

amount each sample recovered its thickness after the compression was calculated, as was the

relative deformation after 24 hours (Table 12 and Table 14). The relative deformation is a ratio

between the change in thickness and the initial thickness ([initial thickness-final

thickness]/initial thickness).

The insulation samples were subjected to a compression test, taken to 10% deformation at a

rate of 3 mm/min. 10% deformation means that the samples are compressed by 10% of their

original size, e.g. a 50mm sample is compressed by 5mm. For each insulation type two samples

were tested and the results of these averaged; these can be seen in Table 12. For the

woodfibre insulation one of the samples increased in thickness from 59mm to 60mm, the other

reduced from 61mm to 60mm. The increase in thickness could be due to the fibres within the

samples being displaced from their original position and finding a new equilibrium position

once the compression was removed. The average of these suggests negligible permanent

deformation of woodfibre board under these test conditions. For the EPS samples, one had no

xxviii

permanent deformation and the other sample a permanent deformation of 2%. Of the three

samples, woodfibre insulation has the lowest relative deformation and phenolic foam the

greatest, approximately 2.5%, when the samples are subjected to a 10% compression test.

Woodfibre Phenolic Foam EPS

Bounce Back (mm) 6.00 3.85 4.35

Bounce Back, % of max.

deformation

101% 76% 90%

Relative Deformation %

((initial-final)/initial)x100

-0.05% 2.5% 1%

Table 12: Relative deformation 24 hours after for 10% compression test of un-rendered

samples

During the 10% compression tests, the stress on the material was recorded, as shown in Table

13. This was compared to manufacturer’s data and predicted compressive resistance of the

material at 10% compression. For the woodfibre board, test 1 shows a very similar strength to

those stated in product data (NBT, 2013). In the second test this is reduced by almost 13%. As

the samples were mechanically cut into appropriate test sizes it is possible that this process

damaged the adhesion between fibres, resulting in a lower compressive strength than

expected. Both phenolic foam samples exceeded the minimum compressive resistance as

specified by ASTM Standard C1126-12a. As the EPS would be utilised in a wall application with

minimal load, it is assumed it is classified as a Type I material for the ASTM Standard C578-

12b. A compressive resistance of 69kPa is suggested for Type I EPS at either 10% deformation

or at yield, whichever of these first occurs (ASTM Standard C578-12b). It can be seen (Table 13)

that neither test results meet this criteria, one by more than 30%. The standard is based on a

25.4mm thick sample but suggests that lower values will result for thicker materials (ASTM

Standard C578-12b, 2012). This might, at least in part, explain the lower test results for the

50mm thick samples used here.

xxix

Insulation Min. compressive

resistance for

10% compression

or yield point

(kPa)

Test 1 Result

(kPa)

Test 2 Result

(kPa)

Woodfibre 704 69.8 61.0

Phenolic Foam 1245 162.5 138.3

EPS 696 61.3 46.4

Table 13: Stress at 10% compressive deformation for un-rendered samples

Insulation and the built up systems were also tested under 50% compressive deformation, and

as before, two samples of each type were tested and the results averaged (Table 14). All

samples at 50% deformation were permanently compacted. The rendered woodfibre samples

had the lowest relative deformation and the phenolic rendered system the largest.

Woodfibre Woodfibre

Rendered

System

Phenolic

Foam

Phenolic

Rendered

System

EPS EPS

Rendered

System

Bounce Back (mm) 20.5 23.5 9.5 9.5 16 17

Bounce Back % of max.

deformation

69% 67% 37% 36.5% 65% 62%

Relative Deformation %

((initial-

final)/initial)x100

16.5% 14.0% 31% 32.5% 17.0% 19.0%

Table 14: Relative Deformation, after 24 hours, of insulation materials and rendered systems,

for 50% deformation

4 Natural Building Technologies, Pavatex- Technical Specification Diffutherm Data Sheet. Available at:

http://www.natural-building.co.uk/systems/new-build/pavawall [accessed 24/10/2013]

5 ASTM Standard Specification for Faced or Unfaced Rigid Cellular Phenolic Thermal Insulation

6 ASTM Standard Specification for Rigid, Cellular Polystyrene Thermal Insulation

xxx

Both compression tests show the same pattern for the material properties. Woodfibre has the

least relative deformation, then EPS and then phenolic foam. Woodfibre insulation is a fibrous

material, and has an elastic response to the compression. The EPS behaves elastically until it

reaches its yield point at 40kPa stress, above which it will undergo permanent deformation.

This is reflected in the relative permanent deformation of the EPS samples, which increased

significantly from the 10% deformation to the 50% deformation. The phenolic foam also

behaves elastically until it reaches its yield point at approximately 120kPa after which

permanent deformation occurs to the insulation. Visible permanent compressive deformation

can be seen in the sample (Figure 18). Examining this at a cellular level, Figure 19, it can be

seen that voids are formed in the closed cell structure. This level of deformation would likely

increase the thermal conductivity of the phenolic foam.

Figure 18: Compressed phenolic foam samples showing deformation in the middle of the

insulation sample, (a) non-rendered sample, (b) rendered sample with full system build up

Figure 19: Phenolic foam samples under optical microscope (a) in virgin state and (b) after 50%

compression

(a) (b)

(a) (b)

xxxi

It is important to consider at what stress the different insulation samples reach 10% and 50%

compression, as this will reflect the likelihood of this occurring to systems once installed on

homes. Table 13 shows the stresses that attained a 10% deformation for each of the samples.

EPS requires the least stress, 53.9KPa on average, to reach a 10% deformation and phenolic

foam the most stress, averaging at 150.4KPa.

The stresses required for a 50% deformation are shown in Table 15, from this it can be seen

that the built up systems require a much higher stress for a 50% deformation, which is part of

the purpose of the fibre reinforcement and render. EPS has the lowest 50% compressive

strength, 136.5KPa, but in contrast to the 10% compressive strength, unrendered woodfibre

has the highest 50% compressive strength, 788KPa, whereas phenolic foam requires a stress of

285KPa for 50% compression. This is due the inherent material properties, once phenolic

foam’s cellular structure starts to break, its strength is weakened and visible compression

occurs, as seen in Figure 18, these are characteristics of brittle behaviour. Whereas, for the

woodfibre board, compression pushes the fibres together so they are more tightly packed,

making it harder to compress and as such the stress required for a 50% deformation is nearly

three times that of phenolic foam and almost six times that of EPS. It should be noted that the

woodfibre samples are 60mm thick compared to 50mm thick EPS and phenolic foam samples.

This in principle should not alter the pattern of results as the load is continuous through the

material structure.

Woodfibre Woodfibre

Rendered

Phenolic

Foam

Phenolic

Foam

Rendered

EPS EPS

Rendered

Test 1 Stress

(KPa)

804 1011 265 318 134 180

Test 2 Stress

(KPa)

772 1055 305 286 139 176

Average Stress

(KPa)

788 1033 285 302 136.5 178

Table 15: Forces and stresses required to reach 50% deformation of sample

It is important to explore what level of forces could be inflicted on the insulation systems in

everyday life in order to understand what level of deformation is likely. In a study of Olympic

boxers (across weight classes) the force from a straight/extended punch ranged from 1990-

xxxii

4741N (Walilko et al. 2005). Kicks would likely generate a larger force than this as more mass

can be recruited. Impacts of this type in a vandalism context would likely fall into the lower

range, but this would be sufficient to cause a 50% deformation in both the EPS and phenolic

foam rendered systems, as from the tests conducted a 50% deformation was reached from

875N for the EPS system and 1484N for the phenolic foam system. The area over which the

impact occurs is also significant, as the stress increases if the same force is applied over a

smaller area. Projectiles with a smaller diameter could potentially cause a higher stress and

therefore more damage to the systems than larger projectiles if the impact occurs with the

same level of force.

From the tests it can be seen that the level of damage to the system also depends on the

material properties of the insulation material. The distinction between the elastic behaviour of

the woodfibre board and the more brittle behaviour of the EPS and phenolic foams leads to

further conclusions. Permanent damage will occur to these materials when applied stress from

impacts exceeds the materials’ yield points. Based on our measurements, EPS and phenolic

foam insulation materials have lower yield points, 40KPa and 120KPa respectively, compared to

200KPa for woodfibre boards; the former are therefore more susceptible to this type of

damage. The more elastic behaviour of woodfibre board will also most likely lead to a

spreading of any applied load over a wider area. This will have the effect of reducing the load

experienced by the material and, therefore, reduce the likely damage.

4 Key Findings and Recommendations

From the impact tests it appeared that the woodfibre samples bounced back after impact,

leaving little indentation in the sample, but some cracking to the render. This was further

demonstrated in the compression tests where the woodfibre samples had the lowest relative

deformation of the three samples tested. The render system did not seem to detrimentally

affect the bounce back and enabled the sample to sustain a higher level of stress before

reaching 50% deformation. The woodfibre boards required the highest loads to reach a 50%

deformation.

The phenolic foam appeared to have a small amount of bounce back in the impact tests. This

was confirmed in the compression tests. The render system improved the compressive

resistance of the foam and did not alter the bounce back. The phenolic foam samples have the

highest compressive resistance for a 10% deformation, but under higher loads, visible

compression and deformation occurs in the middle of the sample and the closed cell structure

is damaged, with voids opening up within it.

xxxiii

The EPS samples consistently have the lowest compressive resistance in the compression tests,

although the rendered system did enable higher forces to be resisted. This corresponds with

the impact tests where there is visibly more compression to the EPS compared to the other

two samples. The visible bounce back is good, and from the compression tests it can be seen

that EPS samples had a higher bounce back and lower relative deformation than the phenolic

foam samples. This is likely due to air gaps being squashed during compression and the

material then expanding again once the loading is released. However, due to the level of the

initial compression, large cracks did form in the impact samples; these would likely allow water

ingress to the insulation.

In the impact tests, both the phenolic foam and EPS samples had higher crack thicknesses as

more boards were joined together. For the woodfibre board samples the three board joint had

a greater crack thickness than the single and two board join, but there was no difference

between the latter two samples. The jointing technique for the woodfibre boards allows them

to act more cohesively, whereas, as can be seen in Figure 12, air gaps are present between

phenolic and EPS joins, so the boards will act independently. Strengthening the four board

joint in particular is recommended for the phenolic foam and EPS systems. Utilising additional

reinforcing mesh over these joints might improve their impact resistance, but this would

require further testing to ascertain.

For all three systems the base rail seems a weak point, improving the impact resistance of this

is recommended. This is a vulnerable and accessible area of the system so may be prone to

vandalism and impacts from projectiles. If repeated impacts cause the base rail to detach this

would then allow significant ingress of water, affecting the thermal performance of the

systems.

xxxiv

5 References

ASTM Standard C1126-12a. 2012. Faced or unfaced rigid cellular phenolic thermal insulation.

ASTM International, West Conshohocken, PA. 2012. Available at:

http://enterprise.astm.org/filtrexx40.cgi?+REDLINE_PAGES/C1126.htm [accessed 24/10/2013]

ASTM Standard C578-12b. 2012. Standard specification for rigid, cellular polystyrene thermal

insulation. ASTM International, West Conshohockhen, PA. 2012. Available at:

http://enterprise.astm.org/filtrexx40.cgi?+REDLINE_PAGES/C578.htm [accessed 24/10/2013]

ETAG 004. 2008. Guideline for European Technical Approval of External Thermal Insulation

Composite Systems with Rendering.

ISO 7892:1988. Vertical building elements – Impact resistance tests – Impact bodies and

general test procedures, (Standard reviewed and confirmed in 2012).

Walilko, T.J., Viano, D.C., & Bir, C.A. 2005. Biomechanics of the head for Olympic boxer punches

to the face. British Journal of Sports Medicine, 39, pp: 710-719

xxxv

6 Appendix

6.1 Supporting information for compression tests

6.1.1 WoodFibre Board Samples

6.1.1.1 Example 10% Deformation Test – non rendered sample

6.1.1.2 Example 50% Deformation Test – non rendered sample

-50

0

50

100

150

200

250

300

350

400

450

500

-2 0 2 4 6 8 10 12

Stan

dar

d f

orc

e [

N]

Deformation [%]

-1000

0

1000

2000

3000

4000

5000

6000

7000

-10 0 10 20 30 40 50 60

Sta

nd

ard

fo

rce

[N

]

Deformation [%]

xxxvi

6.1.1.3 Example 50% deformation test – rendered sample

6.1.1.4 Stress Strain Response of woodfibre samples under 50% deformation

The stress-strain graph is described as a J-shaped curve. As the loading and unloading follow

the same curve, the loading should be completely reversible, hence Woodfibre has an elastic

response, which correlates with its low relative deformation. The Woodfibre insulation stress-

strain graph demonstrates that the material follows Hooke’s Law at the beginning i.e. the stress

is proportional to the strain. As this is constant, the modulus of elasticity, Young’s Modulus,

can be calculated as 0.9MPa using the Elastic Region Response graph; from this it can be seen

that the yield point is at 200kPa.

-1000

0

1000

2000

3000

4000

5000

6000

7000

8000

0 10 20 30 40 50 60

Sta

nd

ard

fo

rce

[N

]

Deformation [%]

-100

0

100

200

300

400

500

600

700

800

900

-0.1 0 0.1 0.2 0.3 0.4 0.5 0.6

Str

ess

(k

Pa

)

Strain

xxxvii

6.1.2 EPS Samples

6.1.2.1 Example from 10% Deformation Tests – non rendered sample

y = 884.85x - 27.256

0

50

100

150

200

250

0.09 0.14 0.19 0.24 0.29

Str

ess

(k

Pa

)

Strain

Elastic Region Response

Series1

Linear (Series1)

-50

0

50

100

150

200

250

300

350

-2 0 2 4 6 8 10 12

Stan

dar

d f

orc

e [

N]

Deformation [%]

EPS Board

xxxviii

6.1.2.2 Example from 50% Deformation Tests – Non rendered samples

6.1.2.3 Example from 50% deformation tests of rendered EPS Samples

-100

0

100

200

300

400

500

600

700

800

0 10 20 30 40 50 60

Sta

nd

ard

fo

rce

[N

]

Deformation [%]

-100

0

100

200

300

400

500

600

700

800

900

1000

-10 0 10 20 30 40 50 60

Sta

nd

ard

fo

rce

[N

]

Deformation [%]

xxxix

6.1.2.4 Stress Strain Response of EPS samples under 50% deformation

As the strain increases, the strain yield point determines the stress needed to induce plastic

deformation in the EPS insulation. The internal cells move to a new equilibrium position. After

the yield point, at approximately 40KPa, permanent deformation of the EPS insulation will

occur.

6.1.3 Phenolic Foam Samples

6.1.3.1 Example from 10% Deformation Tests – non render samples

-20

0

20

40

60

80

100

120

140

-0.1 0 0.1 0.2 0.3 0.4 0.5 0.6

Str

ess

(k

Pa

)

Strain

-200

0

200

400

600

800

1000

0 2 4 6 8 10 12

Stan

dar

d f

orc

e [

N]

Deformation [%]

xl

6.1.3.2 Example from 50% Deformation tests – non rendered samples

6.1.3.3 Example from 50% deformation tests - Rendered Phenolic Foam Samples

-200

0

200

400

600

800

1000

1200

1400

-10 0 10 20 30 40 50 60

Sta

nd

ard

fo

rce

[N

]

Deformation [%]

-200

0

200

400

600

800

1000

1200

1400

1600

-10 0 10 20 30 40 50 60

Sta

nd

ard

fo

rce

[N

]

Deformation [%]

xli

6.1.3.4 Stress Strain Response of phenolic samples under 10% deformation

As the strain increases, the strain yield point determines the stress needed to induce plastic

deformation in the phenolic insulation. The internal cells move to a new equilibrium position.

The sharp dips in the graph demonstrate cracking within the phenolic foam, breaking the

closed cell structure. After the yield point permanent deformation of the phenolic insulation

will occur.

0 20 40 60 80

100 120 140 160

0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.1

Str

ess

(k

Pa

)

Strain

xlii