Retrofit Performance Evaluation

Building on the Leeds Sustainability Institute's (LSI) seminal work which developed the coheating methodology, and provided evidence basis from which the concept of the performance gap was established, the LSI have investigated the extent to which it applies to energy retrofit projects in homes.

Our work has been funded by the old Department of Energy and Climate Change (DECC) and the new Department for Business Energy and Industrial Strategy as well as industry.

Below are case studies related to this research and access to all our research on behaviour change.

Retrofit performance evaluation case studies

Investigating risk and performance of partial and whole house retrofits

This £2.7m is project is funded by the Department for Business, Energy and Industrial Strategy and is one of the largest domestic retrofit projects to have ever been attempted in the UK.  The results on risk and performance will guide future retrofit policy.  It will critique thermal models including dynamic simulation models (DSM) and the Government’s Standard Assessment Procedure (SAP), as well as hygrothermal simulations that are currently used to predict performance and risk, and use building performance evaluation (BPE) field trials, including the Leeds Beckett Coheating Test and novel assessment methods such as the QUB and Pulse testing equipment, to measure and explore how single measure and whole house retrofit impact homes.  The project will involve undertaking 150 surveys to explore why retrofit performance often deteriorates and will also undertake 31 retrofits on case study homes in the North of England. The project is a consortium with the University of Salford who will investigate retrofits in their energy house facility; Loughborough University, who will undertake hygrothermal investigations into retrofits in their laboratory; as well as Lucideon Ltd who will evaluate the properties of common UK building materials in their materials testing facility.

Research outputs

This project is currently in progress, if you are interested in taking part in one of the surveys you can find more information here or contact the LSI to find out more.

Investigations into a phased whole house retrofit in an environmental chamber

The Saint-Gobain Energy House Project was a two-phase collaborative research project undertaken by the LSI in collaboration with the University of Salford and Saint-Gobain Recherché. It was the first full-scale retrofit project ever undertaken in a controlled environment in which the change in thermal performance resulting from the fabric retrofit of a Victorian solid wall house was measured.

Phase 1 of the project involved a staged programme of fabric retrofit to the test house. This allowed the impact of retrofit measures applied to individual thermal elements, combinations of elements and a whole house retrofit, to be assessed. Phase 2 investigated the impact of a whole house fabric retrofit on the retrofitted test house and an untreated adjoining house.

In both Phase 1 and 2, quantitative measurements of thermal performance were obtained from the test house; these included the whole house heat loss value (heat transfer coefficient), in situ U-values and the air permeability value. Qualitative data, such as thermography and construction observations, were gathered to gain greater understanding of the retrofit process and identify potential improvements to retrofit systems. Thermal modelling of all junctions was undertaken to assess the change in thermal bridging characteristics resulting from retrofit. The project also involved work to assess thermal comfort of occupants and experimental work to validate a new dynamic whole house heat loss test (QUB test).

Research outputs

Evaluating retrofits of no fines concrete homes

The Innovate UK S-IMPLER thermal upgrade project was undertaken in collaboration with technology providers Tensor Systems, VRM Technology and the Building Research Establishment all in partnership with the Northern Ireland Housing Executive. As part of the S-IMPLER project, the LSI is directly responsible for testing the in situ fabric performance of dwellings both before and after retrofit. This provides the consortium with valuable data and understanding of the fabric elements within the building. It also allows the group to measure actual improvements in fabric performance and quantifies which elements of the fabric upgrades have been successful. In addition to the fabric testing, the LSI has contributed technical guidance throughout the project, particularly in the development of the retrofit strategy.

Research outputs

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.

Research Outputs

  • Gorse, C.A.,& Glew, D., Johnston, D., Fylan, F., Miles-Shenton, D., Smith, M., Brooke-Peat, M., Farmer, D., Stafford, A., Fletcher, M. and Thomas, F. (2017) Core cities Green Deal monitoring project – Leeds, 2017, Department of Energy and Climate Change.
  • Fylan, F., Glew, D., Smith, M., Johnston, D., Brooke-Peat, M., Miles-Shenton, D., Fletcher, M., Aloise-Young, P. and Gorse C. (2016) Reflections on retrofits: Overcoming barriers to energy efficiency among the fuel poor in the UK, Energy Research and Social Science, 190-198
  • Hardy A, Glew D, Gorse C, Fletcher M, (2018), Validating solid wall insulation retrofits with in-use data, Energy and Buildings, 165, 200-205
  • Glew, D.W., Smith, M., Miles-Shenton, D. and Gorse, C. (2017) Assessing the quality of retrofits in solid wall dwellings, International Journal of Building Pathology and Adaptation, 35 (5), 501-518

Evaluating the performance of novel Internal Wall Insulation

This report presents the preliminary findings from before and after building performance evaluation (BPE) field trials undertaken to measure the impact of 6 TIWI and 1 conventional IWI retrofits. Their impact on thermal bridging and hygrothermal models identified how they affected moisture risk. Dynamic simulation models predicted the energy demand reductions to evaluate potential carbon and fuel bill savings. Coheating test measured the reduction in the heat transfer coefficient (HTC) measured in W/K, which describes the holistic impact on the home’s heating demand.  In addition, blower door tests and heat flux measurements quantified the difference that the retrofits had on infiltration (uncontrolled air leakage) and fabric heat loss, i.e. wall U value measured in W/m²K, respectively. Appraisal of the installation costs and how the TIWI products could overcome installation barriers was undertaken, supported by surveys in 100 homes to identify insulation and dwelling characteristics that affected costs or risks, such as requirements to replace plumbing, boilers & radiators, apply decoration or repair damp walls.

Research Outputs

This project is currently in progress, if you would like any more information, please contact us.

Evaluation of Heat Pump Performance

Harrogate Borough Council has placed itself in the forefront of sustainable development of existing social housing stock by installing Ground Source Heat Pump technology in around 80 properties, with plans for further installations in the future. Ground Source Heat Pumps extract heat at relatively low temperatures from an external ground loop or borehole, and transfer this heat to water in a heating system, raising its temperature sufficiently to provide both space heating and domestic hot water. The system can be supplemented by a small amount of electrical resistance heating to cover any shortfall and to raise domestic hot water temperatures to high levels for short periods, e.g. during pasteurization cycles. Some monitoring of heat pump operation and performance has already taken place and some (limited) contextual information (building type, occupancy, maintenance etc.) is also available. This data has been gathered by Harrogate Borough Council as part of normal operations, without, as yet, any attempt at a systematic analysis of heat pump performance across the Borough. This project aims to systematize existing data, using the conclusions drawn to inform the scope and methodology of future data collection. As far as is practicable at this stage it will assess the energy cost and CO2 savings achieved by the systems, and will develop in-depth case studies of a small number of selected installations via collection of additional data.

Research Outputs

Evaluating airtightness in BISF and solid brick social housing

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.  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 uncontrolled conditions due to occupant activity. Improving air tightness 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.

Research outputs

For more information about this project please contact us.

Quantifying party cavity wall heat loss

Leeds Beckett University and Cambridge Energy were successful in winning a research project from BEIS to investigate thermal losses from party walls. Detailed physical measurements and thermal modelling of heat loss from 54 dwellings with party walls were undertaken, to find out whether interventions are justified nationally.

Evaluating the success of MVHR retrofits

The aim of this project was to assess the effectiveness of the whole house mechanical ventilation and heat recovery (MVHR) systems within the existing UK housing stock.  This was investigated via field trials into homes where MVHR was installed as part of a comprehensive energy efficiency and environmental improvement package. Evaluations were made in terms of energy use, thermal comfort, internal air quality and acceptability to tenants.

Research outputs

Contact the Leeds Sustainability Institute