Dr Felix Thomas

13% of the UK’s total Carbon dioxide emissions are from domestic buildings. Reducing carbon emissions from domestic buildings is an important societal need, this includes older, solid brick walled houses. Solid wall insulation: either internal or external, is the only option to improve the thermal performance of solid brick walls. however; it is also costly and complex insulation to install, and can have several unintended consequences. This thesis focusses on internally installed solid wall insulation, or internal wall insulation (IWI) IWI retrofit can be prone to discontinuities or breaks in the insulation layer, these can be caused by obstructions such as walls or floors. Areas where the IWI layer is broken act as thermal bridges, allowing greater flow of heat through the wall resulting in heat loss and cooling of surfaces at discontinuities which can be at risk of surface condensation formation, potentially leading to mould growth and damage to the building fabric. There are gaps in the knowledge regarding the impacts of discontinuities of IWI in-situ: research in this field has focussed on the use of simulation to assess this risk. The goal of this thesis is to measure the change in moisture risk at junctions of solid brick walled buildings after IWI retrofit, and the impact that discontinuities have on that risk. A field trial was undertaken in a solid brick walled house in which a selection of junctions featuring discontinuities were measured under quasi-steady state conditions. Three IWI retrofits were undertaken in sequence using different IWI systems. In-situ Surface moisture risk was calculated for each junction estimated. Discontinuities of the IWI layer were found to increase the surface condensation risk relative to pre-retrofit. The addition of insulation to discontinuities eliminated or reduced the risk of surface moisture. Simulations were also undertaken to assess the accuracy of the standard approach of assessing surface condensation risk at junctions. Improved wall thermal conductivity and environmental inputs were used in stages to assess how these improved the accuracy of predictions. Simulations were also used to carry out a sensitivity analysis and a parametric analysis of junctions with and without discontinuities of IWI. The sensitivity analysis examined the sensitivity of surface moisture risk to external wall U-value. The parametric analysis investigated how IWI system properties and environmental conditions affect surface condensation at a junction with and without a discontinuity. The findings of this thesis give guidance for the design of IWI retrofits to reduce surface moisture risks at discontinuities of the IWI layer.

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.

Urban green spaces are acknowledged as a vital component in a healthy city, providing a wealth of benefits. Urban green infrastructure (UGI) can help to moderate the intensity of the Urban heat Island (UHI), there is however a lack of high temporal and spatial ground-level data that quantifies the impact of UGI on air temperature and human comfort within UHI areas, and particularly for cities in temperate marine climates, which are not comprehensively understood. This paper therefore uses data from a high-resolution monitoring campaign in the UK city of Leeds to describe the diurnal characteristics of air temperature in grey and green spaces between May and August 2021. Average UHI intensity during this period was 0.9 °K, with a summer maximum of 3.1 °K occurring in late evening. Although there is variation across the monitoring sites, green space was on average 0.7 °K cooler than the grey spaces during the summer months, and up to 2.6 °K cooler on some of the hottest days. Air temperature in urban woods was up to 4.0 °K cooler on the hottest days. These measured data demonstrate the influence of UGI on air temperature in UHI areas, and quantify the impact of different types of UGI, identifying the UGI types that are most effective at regulating higher summertime air temperature. Results presented here provide valuable quantitative data that can support the protection and expansion of urban green space as part of policy development and urban planning in practice.

Whilst it is broadly understood that urban green infrastructure (UGI) helps to mitigate against the urban heat island (UHI) effect, there remains a relatively small body of measured data that quantify the impact of UGI on urban temperatures. This paper presents interim results from a long-term monitoring campaign in the city of Leeds, UK. A network of air temperature sensors housed in Stevenson shields were deployed across Leeds in the summer of 2019. Initially, a total of 17 sensors were included in this network: 10 in grey (man-made built-up areas) urban spaces, 5 in UGI, and 2 sensors at rural reference sites. The data set reported in this paper covers the period July 2019 to November 2020 at an hourly resolution. Results characterise the urban heat island intensity (UHII) and the differences between air temperatures in the urban grey and green spaces. There are both diurnal and distinct seasonal differences in the hourly temperature data. The average UHII during this period was 1.8 °C, with a summer peak of 4.9 °C occurring in late evening. Within the UHI during summer months, the green space was on average 0.5 °C cooler than the grey spaces and up to 2.8 °C cooler on the hottest days. These measured data quantify the local cooling effects of the green space, which is useful at both a macro city-scale and micro citizen-scale. Results of this nature are useful in building a quantitative evidence base that supports the retention and introduction of urban green infrastructure.

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 report presents the findings from part of the Peacock and Verity SHEEPISH Development Stage project, which is funded by the North East and Yorkshire Net Zero Hub’s Energy Project Enabling Fund. The SHEEPISH project aims to develop 15 Silver Street, Masham, North Yorkshire, using bioconstruction materials, particularly sheep’s wool insulation (SWI), become a SWI training site for installers across Yorkshire and the North East, and create a stakeholder cooperative into a robust circular SWI supply chain. Leeds Sustainability Institute has been appointed by Peacock and Verity to consult with stakeholders to find out whether there is support for a Yorkshire-based SWI supply chain, advise on how the performance of SWI at 15 Silver Street could be monitored over time, and perform hygrothermal simulations of building elements at 15 Silver Street to assess whether there are any moisture risks associated with using SWI. Twelve stakeholder interviews were conducted in February 2024 with participants from four stakeholder groups: Yorkshire sheep farmers; general contractors; private and social housing clients; and both SWI suppliers and wool merchants. Participants talked about their current beliefs about SWI, barriers to its use, the potential of developing a Yorkshire SWI market and rationale behind it. Cost was perceived to be the main barrier to increasing use of SWI. Farmers were willing to supply their fleeces if it were financially advantageous to do so, but despite the cost of raw wool making up a fraction of overall manufacturing costs, SWI suppliers and wool merchants thought there would be little opportunity to pay farmers more for their fleeces. There is already a SWI manufacturer based in Yorkshire but for a collaboration to develop, demand for Yorkshire SWI would need to grow. This could be stimulated by promoting the low-carbon, safer-to-install and breathable credentials of SWI to a potential Yorkshire client base, such as private homeowners, prestige commercial organisations, and those with historic assets or a sustainable ethos. Literature on SWI indicates favourable performance for improving air quality, controlling moisture levels and reducing sound transmission. However, most of this data comes from laboratory testing which does not replicate the reality of a product's performance within a construction, highlighting the value of capturing in situ performance data at 15 Silver Street. A range of monitoring options, together with practical considerations, are discussed. We recommend monitoring SWI moisture levels over an extended period and measuring air quality during SWI and conventional insulation installation periods for comparison. Moisture behaviour and breathability of SWI is often considered to be a benefit; however, natural materials can be more vulnerable to decay due to moisture accumulation over time. Hygrothermal simulation models the movement of heat and moisture through materials in a representation of a building element, such as a wall or roof, in response to internal and external climate conditions. Hygrothermal simulation models were used to assess the risk of moisture accumulation over time in selected external elements at 15 Silver Street following a retrofit. Modelling was carried out using the WUFI Pro version 6.7 software for four external wall build ups and three roof build ups, where each case was simulated for a virtual 3 and 10- year period. Overall, hygrothermal simulation indicates that the proposed build ups, including those using SWI, have low moisture risk. In each of the cases modelled, total water content declined over the simulation period or reached an equilibrium state that indicates a low risk of water accumulation in the building fabric. Therefore, the use of SWI appears to be as safe as the wood fibre insulation also specified in the design at 15 Silver Street.

Internal wall insulation (IWI) is one of the few retrofit approaches to reduce heat loss through solid brick walls. Discontinuities in the insulation layer can result in thermal bridges, leading to reduced surface temperatures and the potential for condensation to form. Party wall junctions retrofitted with IWI act as discontinuities when neighbouring homes do not have IWI, leading to reduced surface temperatures on the neighbouring side. The condensation risk imposed on the uninsulated neighbour by a range of notional IWI systems are simulated, the resulting temperature factors indicate whether each system imposes a risk upon the uninsulated neighbour. Thicker, higher performing IWI systems were found to result in greater risk in the neighbouring property.

To construct buildings of the future that are both energy-efficient and moisture-resilient, it is critical to have an in-depth understanding of the varying characteristics of brick properties. This study sampled eight brick-cores taken from solid walled homes across the UK, to investigate the impact of thermal conductivity and hygrothermal parameters on U-values and moisture accumulation. Modelled U-values of uninsulated solid walls, in this sample, ranged between 1.6 and 2.6 W/m2K, with 6 of 8 the homes having surface condensation risks. There was even greater variability found in the moisture content in inner brickwork when simulated in WUFI, between 0.1 to 5.8 %, indicating some bricks are at significantly higher risk of moisture accumulation.

Adopting a fabric first approach and installing thermal insulation in existing buildings is one of the most effective methods of improving energy efficiency. The use of internal wall insulation (IWI) has been shown to offer an effective thermal solution, especially where other methods of insulation are unsuitable. However, fitting internal wall insulation is not without risk as discontinuities (gaps) are often found in the insulation layer for a variety of reasons. This can lead to increased flow of heat from the interior to the exterior causing reduced local surface temperatures, which can lead to condensation or mould growth. Currently there is little or no consistency in the terminology used to discuss such discontinuities in IWI and as such categorising specific types of discontinuities and their relative magnitude and rate of recurrence in practice is difficult. This paper seeks to address the lack of consistency by proposing a taxonomy that practitioners and researchers can use when describing discontinuities in IWI. This paper brings together the findings from building performance research, part of which involved field studies forensically observing IWI installations. Alongside the site visits, a literature review of IWI research was undertaken to identify the types of discontinuities observed and the terminology used to describe the occurrence and characteristics. From this a taxonomy has been developed to standardise and characterise discontinuities. It is hoped this will improve the understanding of and appreciation for the importance and scale of discontinuities in the industry, in so doing setting out a route for reducing their occurrence. It is also proposed that this taxonomy could be adapted for use in discussion of other insulation types.

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.

Urban heat islands are having a detrimental impact on the health and wellbeing of inhabitants in major cities. The impact of global warming is affecting all, but groups, including infants, the elderly and those with poor health are vulnerable and fatalities during hot weather are increasing. High temperatures adversely affect all ages, reducing the ability to function, live and work comfortably and effectively. The planning and design of buildings and their surrounding infrastructure, especially the green assets (trees, plants and vegetation) can reduce the impact of urban heat islands. The problem and challenges of Urban Heat Island are described in this chapter as well as recent research which proposes to capture climate data and the impact of green infrastructure asset and thereby providing guidance for those designing and planning urban developments.

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.

It is not practicable to test every aspect of all the buildings that are built. As we understand the behaviour of buildings from field and laboratory tests the data can be used to produce generalised assumptions about the way a building, and its component parts will behave. These models simulations are now an integral part of our understanding of the performance of buildings. While the assumptions made in models and simulations can be relatively imprecise when first developed, as their development is advanced the models become more detailed, reliable and intelligent. Researchers are constantly updating and calibrating the sensitivity of their models, using new data from the field and in-use studies to improve the reliability and accuracy with which the models can operate. The construction industry is heavily reliant on the use of models and simulations to perform a variety of design and analysis calculations, for predicting energy consumption and performance of finished buildings, and to demonstrate compliance with regulatory or voluntary performance standards.

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.

This book tackles the challenges posed by accelerating urbanization, and demystifies Social Sustainability, the least understood of all the different areas of sustainable development.

Heat exchange between chilled food storage and conditioned spaces in large food retail stores is not currently required as part of design stage regulatory compliance energy performance models. Existing work has identified that this exchange has a significant impact on store energy demand and subsequently leads to unrealistic assessment of building performance. Research presented in this article uses whole building dynamic thermal simulation models that are calibrated against real store performance data, quantifying the impact of the refrigeration driven heat exchange. Proxy refrigerated units are used to simulate the impact of these units for the sales floor areas. A methodology is presented that allows these models to be simplified with the aim of calculating a realistic process heat exchange for refrigeration and including this in thermal simulation models; a protocol for the measurement of chilled sales areas and their inclusion in the building models is also proposed. It is intended that this modelling approach and the calculated process heat exchange inputs can be used to improve the dynamic thermal simulation of large food retail stores, reduce gaps between predicted and actual performance and provide more representative inputs for design stage and regulatory compliance energy calculations.

The York Passivhaus is a 3-bed home in York, North Yorkshire, that achieved Passivhaus certification on completion in 2015. The project aim is to evaluate the building fabric and system performance of the home seven years post-completion against design targets and initial performance tests. Areas of interest are energy consumption, ventilation and air quality, thermal comfort, airtightness and building fabric. Looking at these in turn, fuel bills were used to explore how gas and electricity consumption had changed since occupation in 2016. Gas use was higher during the first year postcompletion in 2016 but has steadily declined since. Electricity use has remained relatively constant. The annual energy consumption in 2023 was 2467kWh for gas (20kWh/m2/year) and 1652kWh (13kWh/m2/year) for electricity, which is between 60 and 74 per cent less for gas and between 9 and 39 per cent less for electricity than the average UK house. The mechanical ventilation heat recovery (MVHR) system was not balanced when flow rate test results were compared against commissioning figures, as extract air flow rates were higher than intake air flow rates. This meant that the system no longer satisfied Passivhaus requirements. Air quality was monitored inside and outside of the home over 12 months. For CO2, a high level of IAQ was recorded, with an average of less than 872 ppm. CO2 levels dropped when the MVHR filters were changed coupled with the onset of warmer weather. Higher noise levels associated with the MVHR system ceased following a service. Higher levels of particulate matter (PM) were recorded at the front of the house, close to a car parking area. Three peak periods were examined to see how particulates generated externally or internally rose and fell over time. Spikes in internal PM levels were generally due to cooking or use of the woodburning stove and dissipated quickly. Elevated PM level patterns recorded outside were often mirrored inside but at a much lower level. Twenty internal sensors monitored temperature and humidity levels. Temperatures remained constant above 15°C throughout winter with all sensors staying within a 3-4°C range, indicating a low level of thermal variation across the home. However, internal temperatures were quite low – usually under 20°C, despite the space heating system defaulting to set points of 24°C during the day and 15°C at night during the winter months. This suggests that the space heating system was undersized for the current occupancy level, as design calculations were based on higher occupancy assumptions. It was assumed at the design stage that the wood-burning stove would meet 30 per cent of the home’s heating demand when during the monitoring period it was rarely used. During warmer weather, higher temperatures were recorded across the two southwest facing first-floor bedrooms. There was no evidence of overheating when the home was occupied during warmer weather. In general, the house is still extremely airtight with a mean permeability of 0.86 m3/(h.m2) @50Pa. However, this is a significant increase in air leakage in relative (rather than absolute) terms since certification was carried out in October 2015, where a mean permeability of 0.39m3/(h.m2) @ 50Pa was recorded. The little air leakage detected appears to come from window seals at casements, the boiler flue, plus some air movement behind plasterboard in the upstairs rooflights, and at wall-to-ceiling, or wall-to wall-junctions. The air leakage area has increased only slightly – from around 73cm2 to 104cm2. Therefore, after seven years the home now satisfies EnerPHit rather than Passivhaus airtightness requirements. A QUB test was used to measure fabric performance. First, a design-stage heat transfer coefficient (HTC) for the home was calculated, which was 69.5 W/K and then tested against. Three tests were done in the summer/autumn of 2022 and two in the winter of 2023. The average measurement was 76.3 W/K. This is a low HTC but 10 % greater than the designstage performance calculation. Overall, as a seven-year-old Passivhaus, the home’s performance is still exceptional compared to current-day new-build homes. Some performance aspects have deteriorated since completion, such as the airtightness and MVHR performance, which could be associated with wear and tear. It is not possible to compare changes to air quality, thermal comfort and HTC, as they were not monitored post-completion. The only area of note is thermal comfort in winter depending on the temperature sought by occupants, as the space heating system is not designed for the current occupancy level and could be considered on the cool side of comfortable.

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.

There remains a significant number of occupied and uninsulated solid wall dwellings in the UK. Deep retrofit is often required for these buildings to become energy efficient but it is difficult to determine how these buildings will respond to retrofit without a detailed understanding of their fabric thermal performance Greater certainty can however be achieved by combining theoretical models and practical field tests, prior to the design of retrofit programmes. This type of approach can then be used to inform and optimize the design of retrofit interventions. This paper presents results from a series of in situ fabric performance tests undertaken on two no-fines concrete, conjoined dwellings pre- and post-retrofit and demonstrates how empirical data can be used to inform and calibrate the thermal performance of dynamic simulation models (DSMs). This is a particularly pragmatic calibration method as it eliminates the need for actual weather data, which is expensive and prohibitive to collect and collate. The DSM inputs and outputs were compared with those obtained from Standard Assessment Procedure (SAP) calculations. The results illustrate how the fabric performance of no-fines concrete can vary between similar house types within the same development. This research also validates the effectiveness of the calibration methodology that uses the whole house Heat Transfer Coefficient (HTC) as the qualifying metric. Furthermore, results also emphasize the importance of appropriately characterizing the physical properties of existing buildings before designing retrofit strategies. This paper contributes to the growing knowledge base concerned with the energy performance gap. In this instance, SAP predicts higher absolute savings then measured in situ which is problematic when assessing the financial viability of retrofits.

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.

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.

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.

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