Dominic Miles-Shenton

Detailed thermographic surveys and pressure tests were performed on newly completed dwellings on 4 Taylor Wimpey sites, encompassing 3 different external wall types; partial-fill masonry (PF), full-fill masonry (FF) and timber frame (TF). Pressure tests were conducted in accordance with the ATTMA TS1 (2016 Edition) protocol. Thermographic surveys were conducted by an ITC qualified thermographer using a FLIR B620 IR thermal imaging camera. An approach of capturing thermal images both externally and internally, and under natural conditions and under depressurisation, was adopted to avoid misinterpretation of individual thermal images. Comparisons between images were then made to distinguish whether thermal anomalies observed on surfaces were due primarily to thermal conduction through the building fabric or due to air movement beneath those surfaces.

Presentation to WDH as part of the Wakefield Affordable Warmth Action Plan

Field Trial Investigations: Research Output for External Body

A presentation to BetterBuilding Ireland. international Conference for a Sustainable Built Environment.

This report sets out the findings from a low carbon housing trial at Elm Tree Mews, York, and discusses the technical and policy issues that arise from it. The Government has set an ambitious target for all new housing to be zero carbon by 2016. With the application of good insulation, improved efficiencies and renewable energy, this is theoretically possible. However, there is growing concern that, in practice, even existing carbon standards are not being achieved and that this performance gap has the potential to undermine zero carbon housing policy. The report seeks to address these concerns through the detailed evaluation of a low carbon development at Elm Tree Mews. The report: * evaluates the energy/carbon performance of the dwellings prior to occupation and in use; * analyses the procurement, design and construction processes that give rise to the performance achieved; * explores the resident experience; * draws out lessons for the development of zero carbon housing and the implications for government policy; and * proposes a programme for change, designed to close the performance gap.

This report details the findings of a project designed to investigate the mechanisms of the party wall thermal bypass in timber framed dwellings. The work was carried out by the Centre of the Built Environment at Leeds Metropolitan University on behalf of Eurisol.

This report is aimed at those with interests in the procurement, design and construction of new dwellings both now and in the coming years as the Government’s increasingly stringent targets for low and zero carbon housing approach. It conveys the results of a research project, carried out between 2001 and 2008, that was designed to evaluate the extent to which low carbon housing standards can be achieved in the context of a large commercial housing development. The research was led by Leeds Metropolitan University in collaboration with University College London and was based on the Stamford Brook development in Altrincham, Cheshire. The project partners were the National Trust, Redrow and Taylor Wimpey and some 60 percent of the planned 700 dwelling development has been completed up to June 2008. As the UK house building industry and its suppliers grapple with the challenges of achieving zero carbon housing by 2016, the lessons arising from this project are timely and of considerable value. Stamford Brook has demonstrated that designing masonry dwellings to achieve an enhanced energy standard is feasible and that a number of innovative approaches, particularly in the area of airtightness, can be successful. The dwellings, as built, exceed the Building Regulations requirements in force at the time but tests on the completed dwellings and longer term monitoring of performance has shown that, overall, energy consumption and carbon emissions, under standard occupancy, are around 20 to 25 percent higher than design predictions. In the case of heat loss, the discrepancy can be much higher. The report contains much evidence of considerable potential but points out that realising the design potential requires a fundamental reappraisal of processes within the industry from design and construction to the relationship with its supply chain and the development of the workforce. The researchers conclude that, even when builders try hard, current mainstream technical and organisational practices together with industry cultures present barriers to consistent delivery of low and zero carbon performance. They suggest that the underlying reasons for this are deeply embedded at all levels of the house building industry. They point out also that without fundamental change in processes and cultures, technological innovations, whether they be based on traditional construction or modern methods are unlikely to reach their full potential. The report sets out a series of wide ranging implications for new housing in the UK, which are given in Chapter 14 and concludes by firmly declaring that cooperation between government, developers, supply chains, educators and researchers will be crucial to improvement. The recommendations in this report are already being put into practice by the researchers at Leeds Metropolitan University and University College London in their teaching and in further research projects. The implications of the work have been discussed across the industry at a series of workshops undertaken in 2008 as part of the LowCarb4Real project (see http://www.leedsmet.ac.uk/as/cebe/projects/lowcarb4real/index.htm). In addition, the learning is having an impact on the work of the developers (Redrow and Taylor Wimpey) who, with remarkable foresight and enthusiasm, hosted the project. This report seeks to make the findings more widely available and is offered for consideration by everyone who has a part to play in making low and zero carbon housing a reality.

An airtight and well insulated thermal envelope is crucial for the development of low energy and low carbon housing. Although this is widely recognized, there is mounting evidence, in housing at least, that the U-values achieved in practice can be much higher than those calculated, and that the gap between the predicted and the actual measured thermal performance of the building envelope can be substantial. This paper describes an approach that can be used in the field to measure the fabric performance of dwellings, a co-heating test. The paper also presents the results from 15 co-heating tests that were undertaken on dwellings that were built to conform to or exceed the insulation requirements contained within Approved Document Part L1A 2006. Whilst the total number of dwellings reported here is small, the results suggest that a significant gap can exist between the predicted steady state heat loss and the measured heat loss, and that this gap can be as much as 125%. This is likely to have significant implications in terms of the energy use and CO 2 emissions attributable to these dwellings in-use.

This paper presents the results and key messages that have been obtained from Phase 1 of a participatory action research project that was undertaken with 5 developers to investigate the practical design and construction issues that arise in making improvements to the airtightness of speculatively built mainstream housing. Two construction types were represented in the project, masonry cavity and light steel frame. Phase 1 of the project sought to assess in detail the design, construction and air permeability of 25 dwellings that were constructed to conform to the requirements of Approved Document Part L1 2002. While the total number of dwellings reported here is small, the results suggest that there is not a consistent approach to the way in which developers present information on air leakage to those on site, a mixture of approaches are utilised on site to achieve the same specification and there appears to be a lack of foresight in the detailed design stage, resulting in specifications that are practically very difficult to achieve. Despite this, the air permeability results suggest that dwellings constructed with a wet/mechanically plastered internal finish, can default to a reasonable standard of airtightness by UK standards, without much additional attention being given to airtightness.

This guide gives an introduction to the topics of airtightness and air leakage and discusses the basic principles of airtightness. It also illustrates a number of areas within masonry construction that may contribute to air leakage and identifies ways in which air permeability of less than 5 m3/(h.m2) @ 50Pa could be consistently achieved in typical UK volume housing.

It is estimated that in the UK, 200,000 residents live in park and holiday homes all year round, the majority of which are elderly and on low incomes. As these homes are often thermally inefficient and leaky, these residents are some of the most susceptible in society to fuel poverty. Despite this, there is a dearth of empirical data available on the in situ fabric performance of these homes. This paper presents the results obtained from undertaking a series of pressurisation tests and leakage identification on new build holiday homes. While the sample size reported is small, the results indicate almost a factor of two variation in the airtightness performance of the homes. In spite of this, all of the homes achieved an air permeability significantly lower than the default value incorporated within the industry standard Energy Efficiency Rating Calculator, suggesting that a much lower figure may be more appropriate. The results also suggest that the use of the air permeability metric within the Calculator potentially biases the performance of holiday homes due to their particular form factor, and that this bias could be mitigated against by adopting the air leakage metric within any future revisions to the Calculator.

The potential to reduce energy demand and thus carbon emissions from the built environment is considerable. As well as benefitting the environment, good energy efficient retrofits can reduce energy bills and improve thermal comfort; however, the discrepancy between expected and actual performance can mean the anticipated benefits are not fully realised. If thermal upgrades are to be accepted and adopted the retrofit solutions should be simple and effective and deliver the performance expected. This paper summarises part one of a two-stage Saint-Gobain funded research project which investigated the change in thermal performance resulting from a number of ‘off-the-shelf’ thermal upgrade measures applied to a circa 1900 solid wall end terrace house situated in an environmental chamber. The project involved a phased programme of upgrades to the thermal elements of the test house; thermal upgrades were applied either individually or in combination. Presented are the quantitative measurements of thermal performance at each test phase which are compared against baseline values measured while the test house was in its original condition. The heat loss coefficient (HLC) of the fully retrofitted dwelling was 63 % lower than the dwelling in its baseline condition. 72 % of the HLC reduction was attributable to the application of a hybrid solid wall insulation system. The fully retrofitted test house had a measured air permeability value that was 50 % lower than in its baseline condition. There was close agreement between the calculated upgrade U-value and that measured in situ for most thermal upgrade measures. The primary conclusion of the paper is that dwellings of this type, which represent a significant proportion of the UK housing stock, have the potential to be retrofitted using off-the-shelf thermal upgrade measures to a standard which meets design expectations and can significantly reduce their requirement for space heating and currently associated CO2 emissions.

Airtightness testing data is increasingly used to inform retrofit design under PAS2035. The processes and experiences of gathering this data offers learning opportunities for residents. Therefore, this paper aims to examine the processes and experiences of airtightness data collection, the data gathered and the value of the data to inform strategies for housing energy retrofit. The perspectives of an engaged resident, who is also a sustainable cities researcher, a building performance expert with over 30 years experience, a qualified thermographer and experienced building pressurisation tester with 20 years experience plus researcher observations are evaluated. Measured air-tightness data are shared (~4 to 8m3.h-1.m-2@ 50Pa), in addition to historical test data, infrared thermography of leakage points and paths, observations of testing processes and experienced perspectives. The contribution is thought on the value of the testing process to inform retrofit, from resident perspectives.

Accurate assessment of both surface and interstitial condensation risk at the design stage of buildings is of great importance - not just to minimise the damaging effects moisture can cause to building envelopes, but also to contribute to the provision of adequate indoor air quality. Guidance certainly does exist with regards to limiting thermal bridging in order to prevent condensation occurring on new constructions. However, a recent study has provided clear evidence that the reality, both in translating the available guidance into a specific design and in construction on site is often rather different from the 'ideal'. This paper reports on that study and compares and evaluates the hygrothermal performance of construction details for different phases during the building life cycle. The results of both the surface and interstitial condensation risk simulations under both steady-state and transient conditions are presented and discussed. Significant differences in the hygrothermal performance of 'standard' and 'as built' construction details are observed.

This report constitutes milestone D11 — Final Report — Domestic Sector Airtightness of the Communities and Local Government/ODPM Project reference CI 61/6/16 (BD2429) Airtightness of Buildings — Towards Higher Performance (Borland and Bell, 2003). This report presents the overall conclusions and key messages obtained from the project through design assessments, construction observations, discussions with developers and pressurisation test results. It also summarises discussion on the airtight performance of current UK housing, the implementation and impact of current and future legislation, and identifies potential areas for future work.

This report sets out, in draft1, the results of the fieldwork phase of research into the impacts of the 2002 revisions to Part L of the building regulations (Approved Document L1 - DTLR, 2001), and the adoption of Robust Details (RDs - DEFRA 2001) on the extent of condensation risk in the construction of dwellings (Oreszczyn and Bell, 2003). The objective of the fieldwork was to explore the practical application of the revised Part L and its associated robust details by housing developers. This was done through a qualitative evaluation of the design and construction of 16 housing schemes designed in accordance with the revised part L and making use of robust details2. The results of the analysis are to be used to enable condensation modelling that takes into account not only the guidance of robust details but also the way in which construction details were actually designed and, perhaps more importantly, constructed. To this end the report identifies 7 areas of construction detailing (yielding some 15 separate detail models) that are to be included in the condensation modelling phase of the project.

This report summarises the main findings of the project ‘Impacts of Improvements to Part L and Robust Construction Details (RCD) on Part C’. The work consisted of a fieldwork element, undertaken by Leeds Metropolitan University and a modelling element carried out by University College London. Details of the work programme are contained in Appendix 1. The fieldwork consisted of the analysis of design material and site surveys from 16 housing developments constructed to Part L 2002 and adopting the Robust Construction Detail route to compliance. The modelling element of the project sought to identify the extent to which the ‘as built’ details give rise to a significantly increased condensation risk as compared to the relevant ‘standard’ robust construction details, as defined in the guidance. In addition to assessing ‘as built’ performance, the modelling phase of the project has investigated the suitability of the relevant calculation methods used to assess the risk of surface and interstitial condensation and mould growth. This report draws together the important conclusions from the project which has previously been presented in several very detailed interim reports and also for the first time presents the results of a workshop where these results were discussed to obtain industry feedback. The overall conclusions, future work and dissemination plans are also presented.

The definition of a sustainable building is not a straightforward one. There are many criteria upon which the sustainability of a building can be judged, including but not limited to energy performance, financial viability and environmental and social impact (Berardi 2013). Any determination of the sustainability of a building will be dependent upon the criteria used to assess it. Much of the work undertaken by the Leeds Sustainability Institute on building sustainability focusses on energy performance in buildings.

This review found that the connecting voids in partially filled cavity walls leads to considerable variation in thermal performance. Whilst photographic records found considerable evidence of gaps in the insulation resulting from poor site practice and installation, research also shows that relatively small breaks between insulation sheets or gaps between the wall and insulation result in a thermal bypass. As the gaps and connecting voids increase air circulation, convection currents and pressure induced exchanges reduce the effectiveness of the thermal barrier. Where effective installation is possible, the topping up of partially filled cavity walls with insulation shows potential to improve the thermal performance of the wall. In the cases reviewed, the installation of blown mineral wool fill reduced variation in heat flow and increased thermal performance. By filling the voids with insulation the passage of air and thermal bypasses were restricted.

For domestic buildings to meet current definitions of zero carbon the building fabric and services must achieve 70% reduction in energy use, taking the carbon emissions down to less than 7 Kg CO2/m2. However, there is a significant obstacle to such endeavours. The limited information on the thermal performance of buildings means that the designs are theoretical. Very few models have been tested against the as-built product and where tests have taken place the cyclical process of research and development is taking time to feed back into the design and construction processes. The gaps in our knowledge of building physics are considerable, designs are not robust and buildings are falling short of their expectations. An intensive study of 18 houses was undertaken to examine the design and onsite assembly, comparisons were made between the predicted energy performance and that achieved once the design was built. The heat losses were, on average over 40% worse than predicted. The forensic analysis of the design and construction process revealed that buildings do not perform as designed due to missing or incomplete information, incorrect detailing, ad-hoc adjustments on site, incorrect assembly of materials, poor workmanship and failure to commission buildings and their services properly. From the research, a list of problems has been produced with the aim of avoiding such defects in the future.

In the UK, there are approximately 330,000 holiday homes spread across a large number of mainly privately owned sites. These homes are often sited in exposed locations, are poorly insulated and are generally heated using expensive fuels, such as electricity or LPG. There is also a lack of empirical evidence available on the in situ energy performance of these homes. Consequently, it is not possible, given the existing evidence base, to determine whether these homes suffer from the same scale of building fabric thermal ‘performance gaps’ (between assumed and realised in situ performance) that have been documented for new build UK housing. This paper presents the results obtained from undertaking detailed in situ thermal fabric tests on five new holiday homes. Whilst sample size reported here is small, the results indicate that a ‘performance gap’ exists for all of these homes. Results obtained indicate that this gap appears narrower than that documented for new build UK housing. The results also suggest that the scale of the ‘gap’ may be more a consequence of the way in which the design intent of these homes has been determined, i.e. a ‘prediction gap’.

In the UK, there is mounting evidence that the measured in situ performance of the building fabric in new build dwellings can be greater than that predicted, resulting in a significant building fabric ‘performance gap’. This paper presents the coheating test results from 25 new build dwellings built to Part L1A 2006 or better. Whilst the total number of dwellings reported here is small, the results suggest that a substantial ‘performance gap’ can exist between the predicted and measured performance of the building fabric, with the measured whole building U-value being just over 1.6 times greater than that predicted. This is likely to have significant implications in terms of the energy use and CO2 emissions attributable to these dwellings in-use.

© 2016 Elsevier B.V. All rights reserved. This paper presents the methodology, along with some of the initial findings and observations from tests performed on two dwellings, of differing construction and form, in which a coheating test was performed using the dwelling's central heating system; this method is referred to as integrated coheating. Data obtained during the integrated coheating tests using a dwelling's heating system have been compared with data obtained during electric coheating of the same dwelling. In one instance, integrated coheating test data from one dwelling was compared to a similar adjoining control dwelling that was simultaneously subject to an electric coheating test. The results show a good agreement between the heat loss coefficients (HLC) obtained using a dwelling's own heating system and those obtained through electrical coheating. Initial analysis suggests the HLC estimate obtained from integrated coheating is likely to be more representative of how a dwelling performs in-use. The findings question the appropriateness of comparing current steady-state HLC predictions to those derived from in-use monitoring data. Integrated coheating has the potential to provide a more cost-effective and informative indication of whole house heat loss than electric coheating, as it enables in situ quantification of both fabric and heating system performance.

While the UK government withdrew from the zero carbon building agenda, the need to provide a high quality, controllable and comfortable internal environment remains. Regardless of the shifting government sands, the thermal performance and energy efficiency of new buildings has improved, creating a gap between new and the 28 million existing properties in the UK. In Britain, many of the existing buildings are draughty and poorly insulated, making the buildings difficult to control and condition; positioning the UK housing stock amongst the most expensive to heat in Europe. Uninsulated thermal elements, bypassing of the insulation layer, and excessive thermal bridging, are present in many of these properties. The resultant cold temperatures and risk of condensation and mould have an impact on the health and wellbeing of the occupants, contributing to excessive winter death rates. To achieve thermal upgrade at scale, affordable and reliable ‘off-the-shelf’ solutions are required. This research provides the results from a deep retrofit project, where off-the-shelf measures were introduced in stages, under controlled conditions, on a hard to treat property. At each stage, significant reductions were achieved in the energy required to heat the property. The whole retrofit provided a more air-tight, thermally efficient fabric that brings many of the environmental benefits associated with new builds

Construction practice has failed to deliver buildings that consistently meet their expected thermal performance; however, examples of good practice do exist. Buildings can be designed and built within acceptable tolerances and meet nearly zero carbon standards. Unfortunately, due to the negative implications associated with the performance gap there have been attempts to divert attention from measurement, with some being critical of methods that were used to identify the variance in building performance. However, the tools have proven reliable and the practice of thermal measurement which was once limited to scientists is finding its place in industry. Measurement is becoming more accepted and different tools are being used to assess thermal performance. The tools can add value to inspections, building surveys and assist with quality control. Construction professionals, not least construction managers, are gaining valuable insights through research undertaken and observations gained. The tests reviewed provide new methods of capturing evidence on building performance, thus allowing valuable information on the quality of design, workmanship and process to be gained. Use of thermal measurement and analysis tools should result in further improvements to building performance. The data from major performance evaluation projects are reviewed and presented

In the UK, approximately 16% of the energy use can be attributed to domestic wet central heating systems. Government financial support and advances in technology have led to boilers becoming more efficient and a range of technologies are now available that claim to be able to improve the efficiency of domestic wet central heating systems. One such low cost technology is a passive deaerator. This paper presents the results obtained from installing a passive deaerator on the closed loop of a gas-fired wet central heating system, under controlled conditions in the Salford Energy House. The results indicate that although marginally less heat output was required from the boiler when the passive deaerator was operating, these savings are more or less out weighted by the boiler short cycling more frequently. Consequently, the overall reduction is gas consumption achieved by utilising the passive deaerator device is only of the order of 0.5%; this scale of savings may just be a consequence of measurement noise. The implications are that although a marginal benefit may be attributed to these products, if short cycling takes place, then these savings may become insignificant.

It is estimated that around 80% of UK dwellings have uninsulated ground floors, representing a significant heat loss mechanism in these buildings. In this research, an aggregated assessment of dwelling heat loss was made using the electric coheating test before and after a ground floor retrofit took place. Heat loss was reduced by 24% (43 ± 18 W/K) indicating that suspended timber ground floor retrofits could improve thermal comfort for occupants and contribute to government domestic energy efficiency policy targets. The findings indicate that disaggregated evaluation methods, such as spot heat flux density measurements, may overestimate the benefits of fabric retrofits. Aggregate methods may therefore be more appropriate tools with which to evaluate retrofits. The U-value improvement resulting from the suspended timber ground floor insulation retrofit, derived via aggregate measurement, was 0.55 W/m²K. Disaggregated spot heat flux density measurements indicated the improvement was 0.89 W/m2K. This research also indicates that Energy Performance Certificates, are unlikely to provide a reliable estimate of energy savings, because they rely on default assumptions for fabric U-Values and ventilation rates. This has implications for policy evaluations as well as householders, who may be excluded from financial support for retrofits.

Fan pressurisation tests (FPTs) are commonly used to measure air leakage in homes, to provide evidence for compliance with energy and ventilation standards in building regulations and inform energy models. The results are presented of 37 pressurisation and co-pressurisation tests on attached homes in the UK which measured inter-dwelling air exchanges during the FPTs. On average, 21% of the air leakage measured by the FPTs was found to be inter-dwelling rather than inside-to-outside air exchange, i.e. homes are more airtight than FPTs indicate, which is important when assessing energy efficiency and ventilation performance thresholds. Not accounting for inter-dwelling air exchanges poses a risk of under-ventilation and misclassification of homes deemed suitable for natural ventilation. Using the FPT result to replace default values for airtightness in energy models used to create Energy Performance Certificates (EPCs) for 11 of the case study homes improved their energy efficiency rating (EER), indicating default airtightness values used in EPCs used were overestimating the air leakage. Using the co-pressurisation value resulted in an additional EER point. These modest improvements represented a 5%, 8% and 3% reduction in predicted annual carbon emission, space heating demand and fuel bills, respectively. Practice relevance The airtightness of homes is fundamental to their energy efficiency and ventilation requirements. The FPT is commonly used to measure airtightness in homes; however, this research has shown that the FPT can overpredict air leakage in attached homes due to the elevated pressures during the test cause inter-dwelling air exchanges not experienced under non-test conditions. This may affect the accuracy of FPTs in attached homes and the appropriateness of using the FPT result to inform building regulation compliance, ventilation decisions and energy models. The research has implications for FPT standards, testing practitioners and professional bodies, energy modellers, ventilation designers, policymakers, and regulations. The development of further knowledge, industry guidance and protocols is required for inter-dwelling air exchange taking place during the FPT, particularly for different house type, form and construction.

The UK Building Regulations sets a maximum airtightness value of 8 m³/m²/h @ 50 Pa for new dwellings, and this is due to be reduced to 5 m³/m²/h @ 50 Pa or less in 2025, when the Future Homes and Buildings Standard is introduced. Compliance with these airtightness requirements must be demonstrated via the fan pressurisation test or more recently the low-pressure pulse test, as set out in CIBSE TM23:2022. Although there is no such maximum airtightness requirement when refurbishing existing dwellings, both test methods are being used to inform retrofit processes. As existing dwellings tend to have more varied and complex air leakage pathways than new build homes, this can pose challenges for the testing methods. However, there is a lack of independent empirical data available which compares high- and low-pressure airtightness test methods in existing dwellings with different airtightness characteristics. This paper presents 88 side-by-side fan pressurisation and low-pressure pulse airtightness measurements undertaken in a range existing dwellings of differing age, size, form and construction type. The results illustrate that there is 2% difference in mean airtightness reported for each test method across the sample, however, the results for individual homes can vary between -84% and 67%. The implications are that there is a need for more investigations into the relationship between high- and low-pressure test methods to ensure they can both be used with confidence to support retrofit processes.

ARC Building Solutions Ltd manufacture, market and distribute a range of party wall cavity barriers. Part L of the Building Regulations (HM Government, 2013) stipulates that when cavity barriers are used for edge sealing purposes, then the seal must be effective at restricting air flow between the party wall cavity and the external wall cavity or external environment (Figure 1). The Building Control Alliance (2011) describes how an edge seal is to be judged as being effective in a qualitative manner. However, there is currently no standard test for quantitatively demonstrating the effectiveness of edge sealing using a cavity barrier product. ARC Building Solutions Ltd wished to quantify the effectiveness of the edge seal that could be achieved using the Company’s products under test conditions. This information could prove useful when engaging designers, building control bodies and warranty providers. As there is currently no quantitative benchmark for what is deemed to be an effective edge seal this project aimed to compare the performance of a recognised ‘current practice’ solution against ARC Building Solutions Ltd.’s T-Barrier, and as far as possible compare these to an accepted effective edge seal for a number of different party wall and external wall cavity widths. In addition to this comparative testing, this project may also assist in the development and application of a standardised ‘Edge Seal Test’ for which there is understood to be no current standard or specific precedent. Whilst the test rig may not be fully representative of the actual construction of a party wall/external wall junction in situ, it is hoped that the results may provide insight as to how the performance of these products may compare in real building situations.

In the UK, it has become apparent in recent years that there is often a discrepancy between the steady-state predicted and the measured in situ thermal performance of the building fabric, with the measured in situ performance being greater than that predicted. This discrepancy or gap in the thermal performance of the building fabric is commonly referred to as the building fabric 'performance gap'. This paper presents the results and key messages obtained from undertaking a whole-building heat loss test (a coheating test) on seven new-build dwellings as part of the Technology Strategy Board's Building Performance Evaluation Programme. While the total number of dwellings involved in the work reported here is small, the results illustrate that a wide range of discrepancies in thermal performance was measured for the tested dwellings. Despite this, the results also indicate that it is possible to construct dwellings where the building fabric performs thermally more or less as predicted, thus effectively bridging the traditional building fabric performance gap that exists in mainstream housing in the UK.

It is recognized that there is often a discrepancy between the measured fabric thermal performance of dwellings as built and the predicted performance of the same dwellings and that the magnitude of this difference in performance can be quite large. This paper presents the results of a number of in-depth building fabric thermal performance tests undertaken on three case study dwellings located on two separate Passivhaus developments in the UK: one masonry cavity and the other two timber-frame. The results from the tests revealed that all the case study dwellings performed very close to that predicted. This is in contrast with other work that has been undertaken regarding the performance of the building fabric, which indicates that a very wide range of performance exists in new-build dwellings in the UK, and that the difference between the measured and predicted fabric performance can be greater than 100%. Despite the small non-random size of the sample, the results suggest that careful design coupled with the implementation of appropriate quality control systems, such as those required to attain Passivhaus Certification, may be conducive to delivering dwellings that begin to ‘bridge the gap’ between measured and predicted fabric performance.

This book focuses on the impacts of the built environment, and how to predict and measure the benefits and consequences of changes taking place to address sustainability in the development and building industries.

Dr Fiona Fylan

With the built environment being one of the largest contributors to anthropogenic emissions, it is essential that building energy demand is controlled, cleaner energy sourced and emissions reduced. However, aligning demand with supply is challenging, as building performance is variable and largely unknown. Central to understanding energy demand is the ability to quantify the energy required to comfortably condition a building and the role that the building envelope plays in effectively enclosing the space. Unfortunately, relatively little is known about building fabric features and how different aspects affect performance under real conditions. Of serious concern and a factor that impacts greatly on control, is the degree that a building’s fabric performance differs from that which is expected. Many buildings do not offer the thermal resistance required to meet their design intent. Where variations in fabric thermal performance are significant this will prove a barrier to the effective use of energy and affect the control of buildings. For effective control, the building demand under different environmental conditions should be relatively stable. The building behaviour and response must be a known quantity. This paper explores air tightness studies in existing and retrofit properties, demonstrating how some buildings have the capacity to be stripped of all conditioned air, while others prove more airtight. Furthermore, results of whole building heat loss tests on new buildings are presented showing the variance in heat loss coefficient, an established indicator of difference in designed v’s as-built performance. The work also demonstrates that energy efficient, thermally resistant, building enclosures can be built within acceptable tolerance; such fabric solutions being key to the nearly zero energy buildings required. The results provide an important step in understanding what is required to achieve the control necessary to move towards energy flexible and efficient buildings.

The methodology used for measuring the thermal performance of fabric retrofit systems which were applied to a solid wall UK Victorian house situated within an environmental chamber is explored in detail. The work describes how steady-state boundary conditions were approximated, then repeated at the Salford Energy House test facility. How established methods of measuring the fabric thermal performance of buildings in situ were adapted to test the effectiveness of retrofit measures within a steady-state environment. The results presented show that steady-state boundary conditions enable the change in fabric heat loss resulting from the retrofit of a whole house or individual element to be measured to a level of accuracy and precision that is unlikely to be achieved in the field. The test environment enabled identification of heat loss phenomena difficult to detect in the field. However, undertaking tests in an environment devoid of wind underestimates the potential reduction in ventilation heat loss resulting from an improvement in airtightness, and hides the susceptibility of retrofit measures to various heat loss mechanisms, such as wind washing. The strengths and weaknesses of the methods employed, the Energy House test facility, and a steady-state environment, for characterising retrofit building fabric thermal performance are demonstrated.

The energy performance of buildings and the ability to accurately predict energy demand is of global importance. As the relative cost and environmental impact of harnessing energy increases so does our need for energy efficiency. Designing, constructing and retrofitting buildings to be more energy efficient requires a thorough understanding of the way each building behaves and responds to its climatic variations. Although the measurement of a building’s energy consumption is straightforward, understanding why consumption differs from that expected requires a detailed and systematic building performance analysis. The way a building is assembled and retrofitted affects performance, thus each aspect of a building’s makeup should be measured or monitored to understand its behaviour. When attempting to understand the performance of a building it is important to consider each element, the components used and the way that they interface to perform as a whole. The measurement of building components in the laboratory is relatively well documented but the testing and measuring of buildings once constructed in the field is an emerging science. This chapter presents the methods used to survey, measure and monitor building performance in the field and how the work is being used to inform the next generation of energy efficient buildings.

Insulating below suspended timber ground floors affects heat transfer at the ground floor to external wall junction, which can affect the risk of surface condensation occurring. In this project, we investigate the impact of installing mineral wool insulation, between joists, below suspended timber floors in 3 solid walled homes. TRSICO is used to calculate surface temperature factors at this junction pre- and post- retrofit. Alternative retrofit scenarios of different combinations of suspended floor and solid wall insulation are also modelled to determine which minimises condensation risk. The results suggest the floor and wall junction will have surface condensation risk when uninsulated. Installing suspended floor insulation increases risk, while installing internal or external wall insulation, with or without floor insulation, reduces risk.

Purpose of the work The purpose of this work is to present the results of a recent study involving a novel ultrasonic technology used to detect and quantify air leaks in buildings and to assess airtightness and air permeability of building envelopes and the individual components within them. Method of approach The approach was to conduct a number of case studies including lab-based empirical verification, semi-controlled environments, and real-world environments including Passivhaus homes and commercial buildings. The new technology was used alongside a variety of airtightness tests. Content of the contribution Energy and carbon dioxide emission reductions from buildings are central to the UK's net zero climate strategy. One factor that can have a significant impact on energy use and CO emissions 2 attributable to buildings is the airtightness performance of the building fabric. Consequently, high levels of building airtightness are crucial if we are to obtain a low-carbon built environment. This paper evaluates the performance of a novel low-cost ultrasonic technology, the Portascanner® Airtight, through comparative testing with existing methodologies, including Blower Door testing, Pulse testing, and thermography. The study found that the most comprehensive evaluation of airtightness is attained when multiple methods, including the Portascanner® Airtight, are used in conjunction with one another. Notably, the Portascanner® Airtight demonstrated a unique capability in identifying leaks that could be overlooked by other technologies, particularly in scenarios where thermography is limited due to unsuitable thermal conditions. Additionally, the study found that the Portascanner® Airtight's quantification of airflow and air permeability closely aligned with results from pressurisation tests, validating its effectiveness as an instrument for airtightness testing. Results and assessment of their significance It was found that the Portascanner® Airtight was capable of detecting and quantifying smaller leaks than any other existing method, to an accuracy of within plus or minus 10% of the true value. It was also found that the instrument could be used in a greater range of applications. Conclusions The most comprehensive evaluation of airtightness is attained when multiple methods, including the Portascanner® Airtight, are used in conjunction with one another. The new technology is particularly useful as an instrument used during construction or retrofitting, to identify leaks prior to completion.

Purpose: The coheating test is the standard method of measuring the heat loss coefficient of a building, but to be useful the test requires careful and thoughtful execution. Testing should take place in the context of additional investigations in order to achieve a good understanding of the building and a qualitative and (if possible) quantitative understanding of the reasons for any performance shortfall. The paper aims to discuss these issues. Design/methodology/approach: Leeds Metropolitan University has more than 20 years of experience in coheating testing. This experience is drawn upon to discuss practical factors which can affect the outcome, together with supporting tests and investigations which are often necessary in order to fully understand the results. Findings: If testing is approached using coheating as part of a suite of investigations, a much deeper understanding of the test building results. In some cases it is possible to identify and quantify the contributions of different factors which result in an overall performance shortfall. Practical implications: Although it is not practicable to use a fully investigative approach for large scale routine quality assurance, it is extremely useful for purposes such as validating other testing procedures, in-depth study of prototypes or detailed investigations where problems are known to exist. Social implications: Successful building performance testing is a vital tool to achieve energy saving targets. Originality/value: The approach discussed clarifies some of the technical pitfalls which may be encountered in the execution of coheating tests and points to ways in which the maximum value can be extracted from the test period, leading to a meaningful analysis of the building's overall thermal performance.

To meet targets on fuel poverty, energy efficiency and carbon emissions existing homes need to be more energy efficient. We report the results of a participatory action research project to explore the challenges associated with energy efficiency retrofit programmes and ways to better implement future schemes. Six focus groups were held with 48 participants from a range of energy efficiency roles. Data were analysed thematically using the research question “What are the challenges presented by implementing energy efficiency retrofit programmes”. We identified four themes in the data: Funding mechanisms; Predicting performance; Installation; and People. Challenges include funding mechanisms for retrofit programmes resulting in insufficient time to plan, publicise, implement and evaluate a scheme and insufficient flexibility to specify the most appropriate intervention for individual homes. Site workers sometimes need to adapt retrofit designs because of insufficient detail from the designer and can equate quality of installation with quality of finish. Landlords and occupier behaviour can impact on the programme's success and there is a need for greater information on benefits for landlords and for energy behaviour change interventions run alongside retrofit programmes for occupiers. There is a need for outcome evaluations of retrofit schemes with the results shared with stakeholders.

Retrofitting solid walled homes is one of the greatest challenges for the UK in achieving its net zero ambitions. Solid walled homes have unique features, that require special consideration. They are among the least efficient in the UK, and their occupants are more likely to be in fuel poverty. They are also at elevated risk of surface condensation, excessive cold in winter and overheating in summer. Retrofitting these homes is a cornerstone of UK policy to tackle fuel poverty and to facilitate the delivery of decarbonised electrified heat into homes. However, installing solid wall insulation is costly and poses more risks of unintended consequences than any other retrofit. Previous projects investigating solid wall insulation have identified major failures when retrofits are installed in a ‘piecemeal’ way i.e., they did not consider how the retrofit measure affects risks of damp, inadequate ventilation, and overheating in homes. This led to the adoption of the whole house approach in new technical standards for retrofit installers (PAS 20351) to ensure that all risks of retrofit measures were always considered, even if only one measure was being installed at a time. Industry is beginning to adapt to these standards, but more research is needed to explore the benefits of adopting the whole house approach, and more guidance is needed to support retrofits in solid walled homes. Insights from this project explain how solid walled homes can be retrofitted more safely and effectively.

The DEEP case study retrofits provide compelling evidence on how a whole house approach to retrofit can reduce heat loss, surface condensation risk and overheating risks in solid walled homes. From the data collected, specific guidance is produced outlining how to install retrofits in solid walled homes more safely and effectively. Recommendations are provided on how to make measurements and modelling predictions of the technical performance of retrofits more accurate. The findings can inform evidence-led decisions at multiple levels to ensure retrofits in solid walled homes are safe and effective.

17BG was one of fifteen case study homes retrofitted in the DEEP project. The case studies were used to identify the performance of, and risks associated with, retrofitting solid walled homes. The data from the case studies was also used to evaluate the accuracy of modelled predictions around retrofit performance and risk.

56TR is one of fifteen homes being retrofitted in the DEEP project. The case studies are being used to identify the performance of, and risks associated with, retrofitting solid walled homes as well as to evaluate the accuracy of retrofit models.

01BA is one of fourteen case study homes retrofitted in the DEEP project. The case studies identify the performance of, and risks associated with, retrofitting solid walled homes. A retrofit was undertaken in stages, reflecting a piecemeal approach to retrofit, followed by undertaking activities that would be required for a whole house approach as a final stage. The data from the case studies is also being used to evaluate modelled predictions of retrofit performance and risk.

55AD and 57AD, are a pair of identical semi-detached homes, and are two of fourteen DEEP case study homes in which the comparison between a whole house and piecemeal approach to retrofit was evaluated.

00CS is one of fifteen case study homes retrofitted in the DEEP project. The case studies were used to identify the performance of, and risks associated with, retrofitting solid walled homes. The data from the case studies was used to evaluate the accuracy of modelled predictions around retrofit performance and risk.

04KG is one of fourteen case study homes being retrofitted in the DEEP project. The case studies are being used to understand the performance of, and risks associated with, retrofitting solid walled homes. The data from the case studies is also being used to evaluate modelled predictions of retrofit performance and risk.

52NP and 54NP are two of fourteen case study homes retrofitted in the DEEP project. The case studies were used to identify the performance of, and risks associated with, retrofitting solid walled homes. The data from the case studies were also used to evaluate modelled predictions of retrofit performance and risk.

This report describes the common data collection and analysis methods used in the DEEP retrofit case studies. These are generically described to avoid repetition in the individual case study reports.

Thermal and hygrothermal simulations are undertaken to estimate energy performance, condensation risks, the potential for moisture accumulation, and timber rot. These simulations use default book values to estimate the material properties of solid brick walls. This report investigates the variability of brick properties found in solid walled homes in the UK and compares these to the default book values. It also explores how varying material property inputs in models affects thermal performance and moisture risk in solid walled homes.

Surveys and air tests were performed at 160 solid and cavity walled homes in Northern England, which had a mix of insulated and uninsulated walls. Blower door tests and Pulse tests were compared and used to quantify the airtightness of the homes. An evaluation of how building characteristics affected the results was performed, and common leakage pathways were identified. Data was also collected on the condition of the homes, potential barriers to external wall insulation (EWI) retrofit, as well as perceptions of occupants.

19BA is a mid-terraced pre 1900 solid walled home where airtightness improvements and room-in-roof retrofits have been installed. Building performance testing has been undertaken to collect data on the performance and risks of these improvements, and to evaluate the accuracy of modelled predictions on the retrofit performance and risk.

07LT and 09LT are two of fourteen case study homes retrofitted in the DEEP project. The case studies have been used to identify the performance of, and risks associated with, retrofitting solid walled homes. The data have also been used to evaluate the accuracy of the modelled predictions of the retrofit performance and risk.

08OL is one of fourteen case study homes being retrofitted in the DEEP project. The case studies are used to identify the performance of, and risks associated with, retrofitting homes without conventional cavities. The data from the case studies are used to evaluate the accuracy of modelled predictions of retrofit performance and risk.

27BG is one of fourteen solid walled DEEP case study homes. In this home building performance tests were undertaken to investigate the success and risk of retrofitting suspended timber floors and how the results compare to predictions.

Wakefield & District Housing (WDH) commissioned the Leeds Sustainability Institute (LSI) at Leeds Beckett University to undertake pressurisation tests and thermographic surveys on 20 semi-detached dwellings (of which only 19 granted researchers access), these were;  14 British Iron Steel Federation (BISF) homes with external wall insulation (EWI)  1 BISF without EWI  2 solid brick properties with EWI  2 solid brick properties without EWI The aim was to identify the influence of EWI on the air tightness of the buildings. The results showed that there was no noticeable improvement in the airtightness of dwellings that had EWI compared to those without EWI in either BISF or solid‐walled dwellings. A larger sample size of BISF homes without EWI and both solid‐walled properties with and without EWI would be needed to assess if this finding was statistically significant. CO2 decay analysis was used in an attempt to validate the blower door results however the results were inconclusive due to a low sample size and an uncontrolled conditions due to occupant activity. Improving airtightness is not the main function of EWI and this has been sustained by our findings. The results confirm that the fabric performance benefit of EWI is restricted almost exclusively to improving wall U‐values, i.e. reducing heat loss through the fabric, not affecting heat loss through uncontrolled ventilation in the dwellings.

Leeds was designated a core city for trialling the Government’s Green Deal domestic energy efficiency policy. Leeds Beckett University undertook a monitoring and testing program on 65 dwellings to investigate the effectiveness of the insulation measures installed and to understand any underperformance. This report outlines the findings from a series of investigations including; surveys, air tightness tests, co heating tests, in situ U-value tests, hygrothermal and thermal bridging modelling, in use monitoring and occupant interviews. The surveys revealed that the ‘whole house approach’ to retrofit was, more often, missing, and quality assurance around insulation detailing was regularly absent, leading to avoidable errors and potentially embedding problems in the installations. Furthermore, moisture issues were, in the majority of instances, over-looked or made worse despite over half the sample having some form of damp. Despite this, energy savings were observed and the appearance of the dwellings were improved, thus apparent satisfaction was generally high, even though the installs were imperfect and moisture problems were introduced. Hygrothermal modelling of IWI cases suggests that thermal bridging at party walls can increase by more than 60% and that there could be potential for rot to embedded timbers. Insulation was recorded to reduce background ventilation of the dwellings by around 25% (a factor unaccounted for in government energy models), although some dwellings were still left with air tightness levels worse than modern day UK Building Regulations limits and replacing wet plaster with IWI was seen to undermine the performance of the insulation. The heat loss coefficient of three homes were tested and showed improvements of 25% and 56% for full retrofits with IWI, and 8% for a party wall retrofit; ¾ of these savings were achieved by fabric improvements and the final quarter from incidentally making dwellings more air tight. The before and after in use monitoring suggested the average savings in energy consumption from all retrofit types (EWI, IWI or other) were between 20% and 29%, although small sampling periods limits the certainty of the results. More reliably it was observed that comfort conditions improved; before the retrofit, 14 of the homes were experiencing discomfort from cold; the retrofit brought on average 2 /3 of uncomfortable homes into more reasonable comfort bands. Nearly all of the occupants had positive experiences, although no householders had to pay for the retrofit, reporting being warmer, bringing unused rooms back into operation and feeling more pride in their homes and communities. A variety of perceptions and behaviours were observed around set point temperatures, use of heating controls and motivations for using energy, all of which contribute to make a complex policy landscape. There is huge potential for domestic retrofit and although this research suggests the current

Thermal performance is often assumed to be constant over the service life of insulation. The aim of this project was to establish the existing evidence on the impact of retrofit degradation over time, and what it means for insulation performance. This report summarises current understanding, classifying key mechanisms for degradation and makes recommendations for how to address identified knowledge gaps.

The benefits and risks associated with installing internal wall insulation (IWI) and thin internal wall insulation (TIWI) retrofits into solid wall homes are researched and evaluated for BEIS. In order to deliver this, a holistic approach was adopted and the project was split into four main sections, each of which has an accompanying Annex to this summary report: Annex A: Review of existing literature as well as primary investigations using house surveys, householder questionnaires and installer focus groups into the sociotechnical barriers to IWI and TIWI. Annex B: Technical evaluation of the performance of IWI and six novel TIWI retrofits installed in field trial solid wall Test Houses using before and after building performance evaluations. Annex C: Modelling of the impact on annual energy consumption, EPC rating, overheating risk, condensation risk and moisture accumulation made by IWI and TIWI retrofits in a range of UK house archetypes. Annex D: Laboratory testing of test walls using hygrothermal chambers to quantify the change in moisture and thermal performance of solid brick walls when they are insulated with IWI and TIWI to determine how weather

From the limited information that exists on the thermal performance of dwellings there is growing evidence of a significant gap between that which is predicted and the built product. Such differences between the intended and actual measured performance are not accepted nor tolerated in other industries. The differences in the performance can be considerable, with some buildings experiencing deviation from designed thermal transmittance resulting in twice the heat loss expected. This does not bode well for the industry when new dwellings are expected to achieve zero carbon standards by 2016. Although some of the problems are related to inadequate design, many are attributable to construction processes. Using the technical reports and feedback from researchers engaged in forensic investigations of building performance, this paper presents some general observations and some re-occurring problems associated with the management of the construction process. Specific areas of concern include the interface between design and construction, sequencing and planning of works, quality of workmanship and build, and lack of quality control systems. Due to current environmental and energy concerns, emphasis has been placed on improving the efficiency of the building system to ensure the gains expected are delivered. Much of this relies on the production of quality building fabrics that provide passive solutions, which maintain thermal comfort and reduce the level of service intervention.

The whole-life sustainability of a building should be underpinned with a demonstration of functional value and an awareness of the direct environmental impact. While a great deal of energy and resources are consumed in the construction of buildings, this is marginal when compared to the operation costs and associated energy used during a building's life cycle. Many reports identify the build costs and associated resources to be less than 1 % of the whole-life operation costs. The exact energy use of a building can vary widely, depending on the use, energy efficiency of the building and occupant behaviour; thus, a greater deal of attention should be given to understanding the energy used in buildings and how energy efficient operation is achieved.

Whole house heat loss or heat transfer coefficient (HTC) measurements are rarely undertaken to validate the performance of retrofits installed in homes. This means policy, certification and householders must rely on predictions made by energy models. Multiple domestic energy models exist, with varying underlying rules and input requirements. This means predictions made by different models may not always agree. However, few studies have compared the predictions from these models with each other, and with measured whole house heat losses for a home before and after a retrofit. This paper compares the HTC of a three bed, semi-detached, solid-walled home measured via the coheating test, with the HTCs predicted by the Reduced Data Standard Assessment Procedure (RdSAP), Building Research Establishment Domestic Energy Model (BREDEM), Dynamic Simulation Modelling (DSM) and the Passive House Planning Package (PHPP). The results show that most predicted HTCs from the models are not similar to the measured HTC, and there is a large variation between the different modelled HTCs. The paper explores why these differences occur and reflects on how to improve the accuracy and consistency of domestic energy models.