Embodied Carbon Guidance For Social Housing
Woodknowledge Wales has created guidance on Embodied Carbon reduction for social housing developers, their consultants and contractors. The guidance contains advice on how to make assessments, available tools and benchmarks for comparison. This briefing paper is designed for strategic leadership teams to highlight the key content of the guidance in the form of a series of questions and answers.
What are the different measures of carbon for housing? For a home, Embodied Carbon is the total carbon emissions associated with the construction materials. It includes all the emissions from the extraction, manufacture, transport and installation of the materials and products needed to construct a home (the Upfront Carbon). It also includes emissions from maintenance, refurbishment, and at the end of life, deconstruction, waste processing and disposal.
Is it the same as Whole Life Carbon? No. The Whole Life Carbon of a home includes both Embodied Carbon and Operational Carbon (e.g. heating and lighting) over its lifetime. Understanding the relationship between both helps to know the best way of reducing carbon emissions throughout the building lifecycle – that’s why Embodied Carbon is being increasingly measured. A Low Carbon home is one that optimises the use of resources to build it and to use it over its lifetime.
Why is it important? Embodied Carbon emissions can represent between 50% and 70% of the emissions of a home across its life cycle. Its relative importance is increasing as the UK’s electricity grid decarbonises and Operational Carbon emissions reduce. At the same time, if the number of additional homes per year matches the estimates of housing need, we will see between 6,700 and 9,700 new homes built in Wales, which will increase Embodied Carbon. Embodied Carbon savings made during the design and construction of a home are delivered immediately, rather than at some point in the future.
Why should we reduce Embodied Carbon? Buildings play a vital role in meeting our climate change obligations, and in Wales, Embodied Carbon accounts for 6% of overall CO2 emissions. The Welsh Government wants all public bodies to be carbon neutral by 2030 and, at the time of writing, most local authorities in Wales have declared a climate emergency. Most of the construction sector is committing to the Net Zero Carbon agenda. Assessing Embodied Carbon will help the sector understand its overall carbon footprint and highlight where reductions can be made. It may also assist in attracting alternative sources of finance such as green bonds. There is also a strong link between Embodied Carbon and the creation of a more Circular Economy.
What are the economic benefits of reducing Embodied Carbon? Targeting Embodied Carbon can help address the whole life costs of a home, especially when future running costs may be more of a concern than initial build costs. For instance, investing in more durable materials will mean less replacement over time, with less Embodied Carbon. This also equates to lower life cycle costs and less tenant disruption. Reducing Embodied Carbon can mean less cost when compared to the cost of solutions for saving Operational Carbon and savings can often be achieved over a shorter period.
How can Embodied Carbon be reduced? Building elements such as the foundations and structure represent the biggest contribution to Embodied Carbon, largely due to the amount of materials they use. Therefore, considering low Embodied Carbon materials such as timber, or increasing the recycled content of materials, will have a positive impact. Timber also has an advantage over other materials as it can store CO2 removed from the atmosphere during the tree’s growth. Designing ‘leaner’ homes by minimising the quantity of materials used to build them will reduce Embodied Carbon. Designing for future use – adaptability and flexibility – will increase a home’s lifespan and minimise the need for new homes in future. Building with deconstruction in mind will enhance the reuse of construction materials.
Is it difficult to measure Embodied Carbon? No, and the earlier Embodied Carbon is considered, the greater the ability to reduce it. Assessments can be in the form of a checklist, simple building analysis or a full building life cycle assessment. It is recommended that a ‘cradle to grave’ assessment is undertaken. There are many tools available to assess Embodied Carbon. Assessments can be done in-house or procured from the design team or a specialist consultant. There are several standards which should be met, including the RICS Professional Statement on Whole Life Carbon.
Can targets and benchmarks be set? Yes, benchmarks (at building or element level) are a useful way to check performance. Woodknowledge Wales has produced benchmarks which can be used as targets for the reduction of Embodied and Upfront Carbon.
Who needs to be involved in reducing Embodied Carbon? Everyone has a responsibility to reduce Embodied Carbon and there needs to be commitment across an organisation to address it, together with an engaged supply chain. Leadership teams should champion and facilitate the reduction of Embodied Carbon in the homes they create.
Is procurement important? Yes, it’s key as it presents an opportunity for measuring, reducing, and managing Whole Life Carbon. At an organisational level, a carbon policy including Embodied and Operational Carbon from housing activities should be agreed, with requirements for reducing Upfront and Embodied Carbon included in project briefs. Performance outcomes can be set in documentation and responsibility for monitoring/measuring Embodied Carbon included at every stage of a building’s life cycle.
DOWNLOAD Q&A (PDF)
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 RICS (2017) Whole Life Carbon assessment for the built environment. 1st Edition. London: RICS. Available at: www.rics.org (Accessed: 2 November 2018).
Home Grown Homes
Embodied Carbon Guidance for Welsh Social Housing Developers, their design teams, contractors and suppliers
This guidance has been written for those wanting to both increase their knowledge of Embodied Carbon in the housing sector and to understand how to reduce it. The target audience encompasses key stakeholders within Welsh social housing organisations including development and asset managers, their design teams, contractors and suppliers.
Clear and authoritative guidance is provided on how to procure and undertake an Embodied Carbon assessment, what benchmarks can be set, tools that can be used and how Embodied Carbon can be reduced. Examples are provided to show how others have tackled Embodied Carbon within their organisations and projects, with a focus on housing. Where relevant, other guidance and useful information is signposted.
Authors: This guidance has been produced for Woodknowledge Wales on behalf of the Home-Grown Homes project. The document was authored by Jane Anderson of ConstructionLCA Ltd together with Katherine Adams, The Alliance for Sustainable Building Products.
Publication date: December 2020
Home-Grown Homes Updates – December 2020
Home-Grown Homes Project on the home run!
The Project which has been the focus for our work since April 2018 formally ends this month. We’ve been studying the timber construction supply chain in Wales and apart from the global pandemic, which didn’t feature in our risk register, it’s turned out to be everything we expected – a significant body of work which altogether makes a compelling case for having an industrial strategy for timber in Wales. Right now Wales is a sheep and steel nation. In the future it needs to become a forest nation.
With our partners BM TRADA, Cardiff Met University and Coed Cymru we have looked at the way the supply chain operates from the growing of the raw material in the forest to its use in creating high-performance affordable homes. We’ve nourished a wider network of organisations to help shape our thinking and develop a raft of practical applications through projects across Wales. In 2020 the public health crisis slowed things up and created challenges we hadn’t foreseen, but we got there in the end!
The main project output is a report which tells the story of the supply chain and the work we’ve done to understand it. We’ve come to some important conclusions about changes which would help to make things work better. We’ve identified a series of interventions which could be made to barriers and improve outcomes for every part of the chain.
The project was conceived before the launch of Welsh Government’s Innovative Housing Programme or the declaration of a Climate Emergency and when foundational economic thinking wasn’t as well developed and widely embraced in Wales. So, to an extent, we’ve sailed on a sea of radical thinking which has both reinforced some of our research ideas and made some of our suggested interventions more urgent. Social landlords want to use more timber in the homes they build, home-grown timber from Wales ideally. They also want to build better and quicker using novel techniques and off-site manufacturing, to create homes which achieve much higher levels of energy efficiency. Carbon reduction has become a new focus for house builders and there are early signs of real interest in the adoption of building performance evaluation techniques to help reduce the ‘performance gap’ in the homes we build.
We have to plant many more trees, that now seems to be widely accepted. And we need to plant more of them for timber, that’s more controversial. We need to develop a more sustainable approach to what to grow and where if we are to diminish our reliance on imported timber and start to see the timber we do produce in Wales used for higher value outputs like timber frame construction, not just fencing, decking, pallets and biomass. We have a sleeping giant of a timber frame manufacturing sector which has, with more support and investment, the capacity and capability to become the off-site manufacturing route some assume we have to develop from scratch or import from ‘over the bridge’. And we need to be supporting our social landlords who are keen to improve their knowledge and understanding and learn new skills in the development of high-performing timber homes.
Our final report includes conclusions around Net Zero Whole Life Carbon homes, reducing embodied, upfront carbon and energy demand, minimising the performance gap, support for off-site manufacturing, carbon off-setting, the opportunity for co-ordinating and consolidating timber supply and demand, forestry investment, our perceptions of conifers, strategic thinking, traineeships and leadership.
The report, which is supported by a number of individual outputs, guidance documents, specification tools and technical briefings, will be available on the Woodknowledge Wales website in early 2021.
Find out more
If you would like to find out more about the project please visit our website page or contact the project manager: David.Hedges@woodknowledgewales.co.uk.
WoodBUILD 2020 Autumn Series – Podcasts
A series of four 60-minute conversations on some of the themes of the Home-Grown Homes Project – Forestry, Manufacturing, Housing and the Foundational Economy. Each podcast features two individuals with a passion for the subject matter and a willingness to share their thinking. David Hedges, Home-Grown Homes Project Manager introduces each podcast and asks the questions.
Our Future Forests
Two chartered foresters in conversation: Jo O’Hara, Managing Director at FutureArk Ltd in Edinburgh and John Healey, Professor of Forest Sciences in Bangor University’s School of Natural Sciences. They discuss our forests, what they look like now, how and why they have changed over time and what the future holds. Plus, forest use, growth and management, culture and history, land use policy, governance and forestry as a career.
|Jo O’Hara||John Healey|
Jo is a member of the Institute of Chartered Forester’s Council – see details here / And you can follow Jo on Twitter @mrsjo
|John Healey refers to his work in Bangor. You can find out more about the University’s work in forestry here.|
Future Homes and how we build (or make) them
Two timber housing manufacturers in conversation: Jasper Meade, Director of PYC Group in Welshpool and Neil Sutherland, Director of MAKAR in Inverness in the Scottish Highlands. They talk about natural materials, high performing homes, change and the barriers to it, specifications, legislation and regulations, energy and carbon, Passivhaus, collaboration, culture, behaviours and more.
|Jasper Meade||Neil Sutherland|
|Jasper is a board member of Woodknowledge Wales and for more information about Jasper’s company, PYC Group, see here.||Neil’s company is MAKAR and their website is here.
You can follow Neil on Twitter @makarneil
Better Performing Homes
Two architects in conversation: Fionn Stevenson is Professor of Sustainable Design in Sheffield University’s School of Architecture and Rob Wheaton is Senior Associate Architect at Stride Treglown. They talk about how different the homes of the future will be from the homes we live in now, sustainability, standards, building performance, architecture education and more.
|Fionn Stevenson||Rob Wheaton|
|Fionn is the author of Housing Fit For Purpose: Performance, Feedback and Learning, published by RIBA Publishing in September 2019. You can read more about Fionn and her work here.
You can follow Fionn on Twitter at @fionnstevenson
|Rob is based in the Cardiff office of Stride Treglown which is a multi-disciplinary employee-owned practice working across the UK. He has recently been working with housing associations on schemes under the Welsh Government’s Innovative Housing Programme. See here.
You can follow Rob on Twitter at @robwheaton
The Foundational Economy
Two Housing Association people in conversation: Debbie Green, Chief Executive with Coastal Housing and Steve Cranston, Foundational Economy Lead at United Welsh. They talk about what the foundational economy is, the pandemic, risk aversion, communities of practice, decarbonisation, listening to people, paradigm shifts and a green recovery.
|Debbie Green||Steve Cranston|
|Amongst other things Debbie, who is based in Swansea, has been chairing the Ministerial Foundational Economy Steering Group. You can find out more about her and her career here and follow Debbie on Twitter at @debbiegcoastal||Steve, who is based in Pontypridd, has been with United Welsh since 2009 heading up their community investment and in the last year, leading their FE work. He’s also had a period of secondment in the Office of the Future Generations Commissioner. You can find out more about Steve here. and follow him on Twitter @stevecr|
Google Map highlights exemplar timber housing projects in Wales
Explore information on construction, innovative products, use of home-grown timber and Welsh manufacturing, carbon impact and building performance in innovative timber housing projects across Wales.
This map showcases the exemplar timber housing projects Woodknowledge Wales has worked on in some way over the past few years. The Exemplar Housing Project layer contains basic project information. The Whole Life Carbon layer contains data on the carbon impact of those projects for which we have undertaken analyses. The Building Performance layer contains projects where we have undertaken some experimentation into different building performance methods. The Forest Nation Attribute layer attempts to capture the timber story such as the use of innovative products, the use of home-grown timber and the use of Welsh manufacturing.
This map represents our progress to date. We will continue to record the progress of our timber development agenda as well as the progress of Welsh housing in meeting the challenge of Net Zero whole Life carbon over the coming years.
VIEW MAP ON GOOGLE →
How to build a Welsh Wood Economy
Why would it be beneficial for Welsh society to build a wood economy? A new report takes a closer look and analyses the economic and social parameters. Get your free copy of the report here and join the dialogue!
The ‘Serious about Green?’ report is authored by the team at Foundational Economy Research, led by Karel Williams. For the first time, it brings together the Woodknowledge Wales forest industries agenda with foundational economic thinking. In a world without silver bullets, we believe the report provides a frank analysis of where we are now, and how a transformative journey to a socially just wood economy can be coordinated.
There’s no doubt this is a challenging agenda. Wales is a sheep, beef and dairy nation and Wales is a steel nation. These activities are deeply ingrained in our cultural identity. They may have been rational activities for the past century but are not well-aligned to the low carbon needs of 21st Century Welsh society. Forestry is.
Furthermore, Wales has a landscape, soil and climate suited to forestry. Well-conceived forestry can address both the biodiversity crises and the climate emergency, whilst providing an industrial resource with which to build and retrofit the low carbon homes of the future.
The report offers insight and stimulating ideas to policy makers, business leaders and citizens interested in a sustainable future for Wales. We invite you to join in a dialogue with us on how to build a foundational Welsh wood economy: firstname.lastname@example.org.
Download your free copy HERE.
Join the dialogue by signing up to our Forests & the Foundational Economy webinar series.
|Date||Time||Title & link to event details and registration via Eventbrite|
|24 Nov||11:00 – 12:30||Serious about Green? Welsh forests and the foundational economy.|
|1 Dec||14:00 – 15:30||Serious about Green? From concept to action|
Valorising the potential of the Welsh green gold reserve
A personal reflection by Dainis Dauksta, technical manager, Woodklnowledge Wales
Conifers grow superbly across many of the microclimates and soil types found in Wales, producing a widely varying range of wood types. However, Wales is caught in a paradox because tropes, assumptions and misinformation still dominate discussions about using Welsh softwoods in construction.
Producing Britain’s finest
Some of Europe’s largest living conifers grow as small stands located in remote parts of Wales but few Welsh firms have been able to create business models which can take advantage of this specialist resource. Large homegrown or ‘’oversize’’ conifer sawlogs have tended to be sold to specialist English sawmills such as East Brothers near Salisbury. Arguably, even Wales’ principal softwood resource, the Sitka spruce sawlog, is not fully understood or utilised within Wales and under-informed commentators still use derogatory language about the ‘’quality’’ of homegrown spruce.
Regardless of such subjective judgments, the British spruce sawmilling sector supplies fit for purpose sawnwood products into demanding modern markets. The UK now produces more conifer sawnwood than Latvia, historically one of Britain’s main suppliers.
Focus on processing efficiencies
Over the last 50 years sawmills across the UK moved away from converting broadleaved species because the markets for homegrown hardwood products went into a steep decline which continues today. The homegrown conifer resource has given British sawmillers the opportunity to modernise and process straight simple conifer stems far more efficiently than converting British hardwoods. Nowadays, sawmills can process softwood sawlogs at line feed speeds of over 100 metres per minute and some chipper canter headrigs can operate at considerably higher line speed. Modern sawlines allow operation at economic scales which make commodity softwoods extremely cheap compared to a generation ago when timber merchants charged up to three times current prices (allowing for inflation).
What if we made homes from it?
Around 700,000 cubic metres of softwood sawlogs are produced in Wales annually. Most of this resource is Sitka spruce and we now know that at least 95% of Welsh Sitka spruce sawlogs will convert to C16 strength class construction timber. A proportion of C24 could also be produced economically.
Roughly speaking, 600,000 cubic metres of sawlogs will yield over 300,000 cubic metres of sawnwood. If only 100,000 cubic metres of that yield was strength graded in Wales this would build 10,000 timber frame homes using 10 cubic metres each. 200,000 cubic metres of non-strength graded sawnwood would still be available. From a theoretical 600,000 cubic metres of softwood sawlogs the remaining 300,000 cubic metres of coproducts (such as sawdust and chipwood) can be utilised currently at Kronospan in Chirk to make wood composite panels.
In other words, all of the 600,000 cubic metres of sawlogs could be utilised in Wales if the Welsh construction sector was able to rise to the challenge. BSW claim that around 40,000 cubic metres of C16 spruce can be processed at their Newbridge on Wye sawmill annually but this output is not directly available for Welsh timber frame firms despite repeated requests.
Dismantling the quality argument
This simplified analysis is made more complicated by the continuing debates about ‘’quality’’ of homegrown softwoods when compared to imported softwoods from the Baltic zone. This straw man argument tends to be utilised by individuals or organisations with historical agendas or close links to Swedish and Baltic timber merchants. In practice, homegrown spruce has been demonstrated to be fit for purpose in timber frame construction.
Over 50 years ago Bruce Zobel, an American forester and wood scientist, made the point that misinformation dominated perceptions of timber grown in modern industrial forests such as our Welsh spruce forests. Today, scientists such as Dan Ridley-Ellis at Edinburgh Napier University confirm that the growth rate of British conifers does not correlate strongly with strength-grading yields. Simply stated, we can utilise almost all of the conifer timber that we grow in varying applications.
Most importantly, utilising quality Welsh softwoods to build homes will help fulfill the Senedd’s aspiration to create a net-zero carbon construction sector within Wales.
Beetles unbalancing commodity markets
Many spruce forests across mainland Europe and Scandinavia are under attack by bark beetles whose numbers have increased exponentially under drought conditions caused by climate change. Traumatised German foresters recently announced that Germany’s parched forests are nearing ecological collapse. Sweden has 7 million cubic metres and Czechia 30 million cubic metres of beetle-ravaged spruce to cut. The resulting oversupply of spruce sawnwood has significantly unbalanced European softwood commodity markets.
British sawmillers were cutting at break-even or at loss-making output prices for many months until the Covid-19 pandemic disrupted world softwood supply even more dramatically than bark beetles. European spruce has been selling at record low prices whilst US and Canadian softwoods have been traded at record high prices.
Cheap imports, price hikes at home
Against this complex backdrop Welsh timber frame contractors are complaining that the home sawmilling sector is unreliable and imported spruce is cheaper and easier to obtain. The current situation is far from normal. We need to redefine the roles of our conifer plantation forests and their downstream processing industries in terms of carbon sequestration and storage.
Preparing for less reliable import markets
Meanwhile, the Covid-19 pandemic will continue to create management problems for the British sawmilling sector. Like any other sector, we need to define the new ‘’normal’’.
In the long term, we may not have the easy access to European, Baltic and Scandinavian softwoods we have enjoyed for centuries. The EU zone has been overcutting softwoods since energy production from woody biomass became fashionable. Furthermore, yields from EU industrial forests will decline after this current glut of diseased spruce processing. Will EU partners be less disposed to selling softwoods into British markets as their own demand rises?
Demand pressures in the net-zero carbon economy
If China is to succeed in turning around their 20th century coal-based economy and create a 21st century net-zero carbon economy, their timber imports are likely to increase substantially. Recently, European prices rose slightly as China increased their procurement of European timber.
If climate change in Wales progresses as predicted by the Hadley Centre, Welsh-grown spruce may transition from commodity to premium softwood. In the face of global warming and concomitant epidemics there is no reason to assume that the status quo can continue.
Managing Welsh forests for future need
Welsh forest management will need to change. The Phytophthora ramorum epidemic has already devastated Welsh larch forests and the forestry sector will need to move away from planting large blocks of even aged single species forest. Some academics suggest that mixed species, uneven aged forests will be more resilient. Existing data does not necessarily support this and other strategies are being discussed. Certainly, forest blocks, whether of single or mixed species will need to be smaller in scale. Individual stands of industrial species will need some social distancing in order to decrease risk or speed of disease spread.
What if freestyle forestry was the answer?
Welsh foresters will need to design new forests that can be managed in the face of waves of weather events, pests and pathogens; principal interventions may need to be predominately reactive. Some central European foresters are calling this ‘’freestyle’’ forestry. The narrative about growing our own forests for making new homes will be continually altered as events unfold. The only certainty is that uncertainty will rule sustainable forest management. In spite of this, we have to start planting now for the future. Mistakes will be made and circumstances change but surely that is better than not planting at all?
Home-Grown Homes Updates – September
With just a few months left of the Home-Grown Homes Project we are now focused on pulling together all findings from the research into usable design guides and tools to leave a lasting legacy from the project.
Project Governance update
The project’s steering group met in September. It reviewed project progress and in particular discussed a draft second interim report and a proposal for a second phase when the current project ends. Cardiff Metropolitan University Research Associate Diana Waldron gave a presentation on progress with the building performance element of the project. The steering group confirmed a three-month extension of the project (until the end of March 2021) for this work package to be completed.
The importance of timber supply chains in Wales
Since the project’s inception, four important developments have served to emphasise the relevance and importance of the timber supply chain in meeting current Welsh Government policy objectives:
• the influence of foundational economic thinking
• the declaration of a climate emergency
• the decision to leave the EU and
• the coronavirus pandemic
A draft of the second interim project report has been prepared to reflect these developments and to draw together the findings from the Home-Grown Homes project, identifying a series of interventions along with a suite of unique behaviour change tools in the form of guidance and case studies. The draft is currently being reviewed by the project steering group, when complete it will be shared with stake stakeholders and the collective feedback will help to shape the final report in December.
Project promoted during Ministerial meeting
Woodknowledge Wales Chief Executive Gary Newman met with Julie James MS Minister for Housing and Local Government at the end of September. The meeting provided an opportunity for the Minister to learn more about the work of WKW, achievements made in projects like the Home-Grown Homes Project and plans for future activity and where this might support Welsh Government priorities and action.
Further revisions have been made to a series of reports on the use of the Overheating in New Homes Tool developed by the Good Homes Alliance. A thermography report on Pentland Close in Cardiff is being reviewed ahead of publication. Refinements have been made to the detail and preparation is being made for the soft launch of the two industry guidance tools on Building Performance Evaluation and Embodied Carbon in October. For more information contact Diana Waldron (email@example.com).
Timber Frame solutions
BM TRADA colleagues are finalising a number of guidance documents and project outputs (detailed in previous updates) after some of them were furloughed. Guidance on Design, Production and Erection will identify the common issues which timber frame homes present during design and construction and how these can best be avoided.
WoodBUILD autumn series – webinars underway!
Our webinar series has started with the first two on the themes of forestry and housing being held on-line attracting lots of interest and engagement. The first focussed on Productive Forests and Climate Smart Woodlands and looked at woodland management, what we should we plant and what tools can help in making choices. Tim Pagella of Bangor University, Duncan Ray of Forest Research and Chris Jones of NRW shared their thoughts and responded to some challenging questions in a facilitated discussion.
The second webinar explored building performance in social housing. Diana Waldron of Cardiff Met University, Julie Godefroy of Julie Godefroy Sustainability and Susie Diamond of Inkling and Grant Prosser of Wales & West Housing explored the growing interest in this area of research and practice and included a soft launch of forthcoming guidance and an update on the progress being made in the Home-Grown Homes Project in this area.
Autumn Conversation Podcasting
A series of four podcasts are being finalised which link to the project themes and will be published on-line by mid October. Lasting about an hour they each feature a conversation between two individuals with a background and interest in the subject matter and focus on the future and how it might be shaped. The four themes and conversationalists are:
- Bangor University’s John Healey and forestry consultant Jo O’Hara talk future forests;
- PYCs Jasper Meade and MAKARs Neil Sutherland talk about manufacturing homes;
- Coastal’s Debbie Green and United Welsh’s Steve Cranston explore foundational economic responses;
- Sheffield University’s Fionn Stevenson talks about our future homes with Stride Treglown’s Rob Wheaton.
If you would like to find out more about the project please visit our website page or contact the project manager David.Hedges@woodknowledgewales.co.uk.
Net-Zero targets for Wales
Building on the work of the UKGBC and LETI, the Home-Grown Homes Project have developed a graphical net-zero guide with a set of targets & principles that we believe are achievable within a Welsh context. The guide is aimed at helping developers, designers and manufacturers achieve net-zero whole life carbon. This means tackling upfront carbon, energy demand, use of renewables and embodied carbon in order to reduce the overall emissions associated with any proposed development.
Later this year we will publish a set of additional supporting guides that run alongside this graphic, describing, for example how to measure and reduce embodied carbon, a zero-carbon design guide using typical Welsh timber frame systems, and a guide to support building performance evaluation to address the energy performance gap.
Demonstration of Practical Building Performance Measurements
Woodknowledge Wales (WKW) believes that we can only improve the performance of housing and really deliver zero carbon through the measurement of whole life carbon and testing of building performance. Otherwise we live in the dark.
How do we make building performance measurement practical and affordable?
Woodknowledge Wales and Cardiff Metropolitan University recently carried out detailed performance measurements on two newly built timber frame low rise blocks of flats as part of our Home-Grown Homes Project. The purpose of the work was to test out novel methods of building performance evaluation being pioneered by Build Test Solutions (BTS), who specialise in making practical building performance measurement technologies.
The two building projects participating in the testing were:
- Pentland Close, Cardiff, a development for Wales and West Housing Association. Built by Hale Construction who procured Sevenoaks Modular as a specialist timber structures supplier using their Trisowarm system.
- Croft Court, Welshpool, a development for Mid-Wales Housing Association. Built by Mid Wales Properties Ltd, who contracted AC Roof Trusses to provide the timber frame.
Both projects were designed with high thermal performance aspirations, and the measurements have shown that this high performance was delivered in practice. WKW hope that these measurements could provide the template for as-built performance measurement testing in the future.
The performance testing enables the contractors to demonstrate the quality of their work and providing quality assurance to their clients.
The Clients Perspective
Grant Prosser from Wales and West Housing Association commented that
“these measurements for the first time allow us to quantitively assess the energy performance of the built product at completion, as the performance gap is a significant concern for us as it negatively impacts on our residents this is fantastic quality assurance on this project and could be a great way for us to inform our product selection and work with contractors to provide high quality, low carbon new homes.”
The Manufacturers Perspective
Matt Hall from Hale Construction said that
“it’s been great to be involved in the project and get assurance of the quality of our work. We pay close attention to detailing to achieve the design airtightness and limit thermal bridging and it’s great to see the proof that this pays off”.
Thermal Performance and Buildings
Thermal performance refers to building’s ability to retain heat, so that when the performance is higher the dwelling can be heated inexpensively and with lower consequent emissions. It is measured by the Heat Loss Parameter (HLP), which is a measure of the rate of heat loss per degree of temperature difference between inside and out per m2 of floor area.
The performance gap is a much-researched phenomena in buildings, where the actual thermal performance is typically worse, and sometimes much worse, than the design expectation. For example, the Building Performance Network’s recent State of the Nation report which was part funded by Woodknowledge Wales found that in their sample of 29 buildings measured, 20 performed worse than expected by an average of 18% with an extreme case 100% worse than predicted.
Heating buildings accounts for around a third of all emissions in the UK, and addressing these emissions is therefore a key part of any national decarbonisation plan. At present all policy in this area is based on predicted, rather than measured performance, this is largely driven by a lack of practical methods to measure building performance.
How to Test Thermal Performance in Buildings
Currently the most widely used method to measure building thermal performance is called the co-heating test, it has been a crucial tool in revealing the performance gap but at a cost of thousands of pounds per test and requiring a building to be empty for two weeks it is not practical on a wide scale.
Build Test Solutions make building performance measurement equipment and methods to address this gap, which they applied alongside traditional methods on these two demonstration projects. The measurements included airtightness using BTS’ Pulse equipment and a blower door test, whole building thermal performance using BTS’ SmartHTC and a co-heating test and the thermal performance of the external walls using BTS’ heat flux plate kit. Richard Jack, a product manager at BTS, said that
“this project is an excellent demonstration of a full range of thermal performance measurements, and an excellent opportunity to engage with clients, manufacturers and contractors to understand how the measurements can help inform their processes”.
Croft Court, Welshpool
In Croft Court, the performance measurements were carried out in a top floor flat, for each measurement the measured performance was very similar to the design value.
This suite of measurements allows not just a judgement of the overall thermal performance, but also allows sources of heat loss to be further broken down through different heat loss paths.
Pentland Close, Cardiff
In Pentland Close, measurements were carried out in a top and bottom floor flat and for each showed close agreement with the design values. Data collection for the SmartHTC measurements in these flats was interrupted by the movement restrictions imposed by COVID-19 which means these results can’t yet be calculated.
|Pentland Close. Ground Floor Flat||Pentland Close. Top Floor Flat|
The difference in performance between the two flats is caused primarily by the adjacency of the ground floor flat to an unheated buggy store. By comparison, the top floor flat (which is of the same dimensions) is next door to another heated flat and hence assumed to have no heat loss through the equivalent wall. This results in an extra source of heat loss through the internal wall between the two and also a higher calculated thermal bridging due to larger exposed area. The breakdown in heat loss for the two flats shows this additional heat loss to the buggy store.
Comparing different Build Projects
Beyond the comparison with the design figures for each flat, it’s also possible to consider what level of performance the flats reach in comparison with others.
At present, fabric performance metrics are not common measures of the energy performance of dwellings, with the Energy Efficiency Rating from the Energy Performance Certificate the most commonly used metric. The Energy Efficiency Rating is based upon the expected cost of fuel consumption to heat a dwelling, calculated using the Standard Assessment Procedure (SAP). This calculation is based upon the thermal performance of the dwelling, but also an assumed occupancy pattern, the efficiency of the heating system and the assumed cost of energy (gas and/or electricity). The Croft Court flat has solar PV panels which significantly offset the cost of electricity, and hence result in a higher (better) EPC rating.
|Croft Court||92 (A)|
|Pentland Close ground floor||81 (B)|
|Pentland Close top floor||82 (B)|
Measuring fabric performance
A building’s thermal performance is key to its energy performance and thermal comfort, it is fundamentally important because the building will likely last longer than its systems or occupants. As such it makes sense to consider a specific fabric performance metric such as the Heat Loss Parameter, alongside the EPC rating, promoting a fabric-first approach. The HLP has previously been used as a key performance indicator in the Code for Sustainable Homes.
All three flats measured display high levels of thermal performance, with insulation levels similar to those recommended in schemes such as Passivhaus (though with higher air permeability). This is clear when comparing the measured HLPs in these flats, which ranged from 0.65-1.00, with the HLP scale produced by BTS.
The performance measurement demonstrations provide quality assurance on these three flats, and a demonstration of what’s feasible using performance measurement. Diana Waldron from Cardiff Metropolitan University, project partners on the Home-Grown Homes project, summed up the project as;
“a unique opportunity to gain further understanding in the area of building performance evaluation methods, aiming to find ways to make them more approachable to all relevant actors in the building industry. All the learning captured during this investigative work will be further disseminated, put into practice and re-tested, in tandem with our main aim: to achieve better quality homes in Wales”.