The UK government’s Department for Energy Security and Net Zero (DESNZ) recently published the Demonstration of Energy Efficiency Potential (DEEP) report, which explores how different retrofitting methods can improve the energy efficiency of the country’s older housing stock, particularly solid-walled homes. Developed in partnership with Leeds Beckett University, the University of Salford, and Loughborough University, this extensive study offers crucial insights into best practices for retrofitting. With airtightness as a core theme, the DEEP report highlights the need for reliable testing methods to ensure energy efficiency improvements in existing buildings. For the Air Tightness Testing & Measurement Association (ATTMA), this report reinforces the importance of airtightness testing in the retrofit process.
The DEEP project’s goal was to answer fundamental questions: What are the most effective ways to improve energy efficiency in solid-walled homes? How can the risks, such as condensation and overheating, be minimised in retrofits? Through rigorous testing, the report presents data-driven recommendations to support the construction industry, homeowners, and policy developers in creating effective retrofit strategies.
“The DEEP report presents a detailed roadmap for retrofit success, combining airtightness with effective insulation and ventilation measures to ensure real energy savings in the UK’s existing housing stock,” says Barry Cope, Managing Director of ATTMA. “Our focus at ATTMA is to promote airtightness methods, like blower door testing, which have proven time and again to provide accurate, reliable data for retrofit planning. This report validates that approach.”
For ATTMA, the DEEP findings align closely with its long-standing commitment to airtightness testing, which has become a key measure for accurately assessing energy loss new builds and retrofit projects.
Why Airtightness is Essential in Whole-House Retrofits
The DEEP report’s findings underscore the significant energy savings achievable through airtightness improvements. In trials conducted across 14 case study homes, reducing air leakage by addressing common pathways – such as gaps around windows, doors, and floor junctions – resulted in whole-house heat loss reductions of up to 36%. Notably, airtightness improvements alone were shown to reduce household energy bills by up to 8%, depending on the original leakage levels This is particularly relevant when considering the average ‘medium’ household energy bills are £1727.27[1], which means an average saving of £138.18 per annum just from air sealing. This could be as much as £192.28 for larger homes. When combined with further retrofitting, such as solid wall insulation, air leakage reductions contributed to overall energy savings of up to 60% in specific homes. These improvements not only translate into lower energy costs but also represent a critical step in meeting future energy performance standards, especially as airtightness strategies are integrated into the whole-house retrofit approach.
[1] www.uswitch.com/gas-electricity/guides/average-gas-and-electricity-bills-in-the-uk, accessed 2024.
Airtightness testing is more than just a diagnostic tool; it’s an essential component of a whole-house approach to retrofits. By reducing air leakage, professionals can enhance the effectiveness of other energy-saving measures like insulation and ventilation systems. Without airtightness, energy-efficient measures can underperform, leading to uncomfortable draughts, high heating costs, and potential condensation issues. In buildings where airtightness has been overlooked, other retrofits simply cannot achieve the full potential for energy savings.
The DEEP report recommends airtightness testing as a precursor to retrofitting work to develop an accurate performance baseline. “Achieving airtightness first enables us to ensure the whole-house approach is applied effectively,” Paul Carling explains. “For solid-walled homes, managing airtightness upfront is essential for reducing heat loss and preventing common issues like condensation.”
The Importance of a Comprehensive Airtightness Strategy
While blower door testing identifies leakage points, the DEEP report highlights the need for a well-rounded airtightness strategy to maximise energy savings. Traditional draught-proofing methods can improve airtightness to a degree but often fall short of the standards needed for comprehensive energy savings, especially in older homes. As the report notes, “Draught-proofing may provide some improvements, but whole-house airtightness strategies are required to meet the airtightness needs of today’s energy efficiency targets.”
ATTMA advocates a strategic approach to airtightness that includes sealing windows and doors, insulating suspended timber floors, and addressing thermal bridging at wall and ceiling junctions. This kind of airtightness strategy does more than cut energy bills; it also future-proofs retrofits by preventing moisture issues, mould, and structural deterioration.
Key Findings from the DEEP Report on Retrofit Strategies
The DEEP project conducted studies across multiple universities and organisations, seeking to understand the most effective energy-saving measures for solid-walled homes. One of the report’s standout findings is the importance of the whole-house approach to retrofit, which involves assessing and upgrading each element within a building’s fabric to work cohesively. This approach ensures retrofits are effective, cost-efficient, and minimise risks such as moisture and condensation issues, which are prevalent in solid-walled homes. According to the report, “Effective energy efficiency improvements require a comprehensive approach to airtightness and insulation, particularly where multiple retrofits interact to impact the building’s overall performance.”
The Potential of Reduced Data SAP in Expanding the Retrofit Market
One of the more promising developments for retrofitters is the use of the Reduced data Standard Assessment Procedure (RdSAP), a streamlined approach to assess existing homes’ energy performance. RdSAP is particularly valuable for accurately predicting the impact of airtightness improvements on heat loss and energy ratings. The DEEP report illustrates how integrating airtightness data from blower door testing into RdSAP calculations could unlock significant potential for the retrofit market, particularly in the case of solid-walled homes.
“Integrating airtightness test data with RdSAP could unlock a new market for energy efficiency improvements in existing homes,” says Mr Cope. “This integration allows for much more accurate assessments, which in turn gives homeowners confidence in the projected savings they’ll see after a retrofit.”
Low Pressure Pulse Testing
The DEEP report identifies both advantages and limitations in low-pressure pulse testing, which has emerged as an alternative in some contexts. Pulse testing is noted for its ease of use and being less intrusive, making it potentially suitable for specific scenarios. However, in older buildings with variable leakage paths, pulse testing can occasionally miss critical areas of air leakage, making fan pressurisation and depressurisation testing preferable for comprehensive retrofit assessments. The DEEP report notes, “While low-pressure pulse testing may be appropriate in tightly controlled environments, blower door testing remains essential for capturing the complexity of air leakage patterns in older or solid-walled homes, where a detailed analysis is crucial.”
Paul Carling, ATTMA’s Technical Manager discusses, “Blower door testing remains, for our members, the preferred option; it’s a necessity in accurately diagnosing and resolving airtightness issues, particularly leakage from homes that have a very high level of infiltration.”
Mr Carling goes on to say “There are myths about low pressure Pulse being a more accurate representation, but this simply isn’t true. A blower door fan can comfortably test at 4Pa but we do not, simply to remove the uncertainty of measurement. Being able to test at a range of pressures gives options for diagnoses and deeper understanding of the effects of pressure on the building”.
Mr Carling balances his view by discussing the positives of low pressure testing, “It will appeal to those involved in existing home testing, especially for homeowners looking to improve their EPC without making modifications to their home. Its ability to be set up and pressurised outside the property allows for faster measurements inside. However, as this report highlights, for Retrofit it is essential to locate those leaks, not just provide a datapoint.”
The DEEP Report: A Call to Action for Industry Professionals
The findings of the DEEP report underscore ATTMA’s long-standing advocacy for high-quality, consistent airtightness testing. As the cornerstone of a successful retrofit, blower door testing provides the depth and dependability needed to inform comprehensive retrofit planning and evaluation. For professionals in the field, this report serves as a call to integrate blower door testing as a standard practice, ensuring that airtightness is assessed comprehensively and that improvements are based on accurate data.
This report aligns with our mission at ATTMA to ensure that every home, especially those undergoing retrofits, benefits from reliable and thorough airtightness assessments – Barry Cope, ATTMA Managing Director
ATTMA’s Managing Director, Barry Cope, sees the DEEP report as a significant validation of the organisation’s mission: “This report aligns with our mission at ATTMA to ensure that every home, especially those undergoing retrofits, benefits from reliable and thorough airtightness assessments. As the UK progresses towards its net-zero goals, we’ll continue to advocate for high standards in airtightness testing, ultimately helping professionals and homeowners alike achieve meaningful energy savings, as well as comfortable living spaces.”
Training, Expertise, and the Future of Airtightness Testing
Quality airtightness testing requires skilled professionals who are trained to conduct airtightness tests according to the highest standards. ATTMA is committed to providing the necessary training and certification to equip professionals for today’s market demands and to prepare them for future advancements in airtightness testing.
“There is a skill to airtightness testing that shouldn’t be underestimated,” says Paul Carling. “Proper blower door testing is a precise scientific process, and training is vital to ensure these tests are conducted to a high standard, particularly in the retrofitting space.”
Looking Ahead: Airtightness Testing as the Benchmark for Retrofit Success
As the demand for sustainable, energy-efficient housing continues to grow, blower door testing is set to become the benchmark for airtightness assessment in retrofits. Supported by findings from the DEEP report, blower door testing provides the comprehensive, actionable data needed to drive effective retrofitting. The expanded use of RdSAP in the retrofit market, combined with robust airtightness standards, will allow for precise energy performance predictions, encouraging both professionals and homeowners to invest in energy-efficient upgrades.
ATTMA stands at the forefront of this movement, advocating airtightness testing that ensures not only compliance but also tangible, long-term energy savings. As the DEEP report demonstrates, high standards in airtightness assessment are foundational to achieving the UK’s ambitious net-zero targets and improving the quality and comfort of the nation’s housing stock.
The reports from can be downloaded here: https://www.gov.uk/government/publications/demonstration-of-energy-efficiency-potential-deep
