The government’s Warm Homes Plan will spend an estimated £6 billion over this parliament on upgrading the UK’s least efficient homes. But BSRIA, the building-services research body, has a sobering message: without mandatory performance testing, much of that money could be wasted on retrofits that look good on paper but fail in practice. As reported by fmj.co.uk, BSRIA’s case is simple: test what you install, not just what you design.
What BSRIA is actually proposing
BSRIA wants every domestic retrofit project to undergo a standardised performance test after installation. This is not a tick-box exercise. They recommend measuring airtightness with a blower door test, checking heat pump coefficient of performance (COP) under real winter conditions, and using thermography to spot insulation gaps. The idea is to catch the 30-40% performance gap that studies from the Department for Energy Security and Net Zero have repeatedly found between modelled and actual energy savings. For a typical 3-bed semi using 12,000 kWh of gas a year, a 30% gap means losing about £240 annually on a £1,800 heating bill.
Who pays, and who benefits
The catch is cost. A blower door test runs £250-£400. A thermographic survey adds £150-£300. For a full heat pump performance verification, you might pay £500-£800. On a £15,000 retrofit package, that’s 5-7% extra. Private homeowners could absorb it, but the Warm Homes Plan is meant to target low-income households in EPC D-G homes. If the government mandates testing but doesn’t fund it, those households lose out. If it funds it, the Treasury needs to add roughly £200 million to the programme budget, based on 1.5 million homes at £350 average test cost. Ofgem’s modelling for the Energy Company Obligation suggests every £1 spent on quality assurance saves £3-£5 in remedial work and lost savings.
What this means for your EPC and your bills
Current EPCs are based on standardised assumptions, floor area, wall type, boiler age, not measured performance. A retrofit that passes a blower door test can lift an EPC from D to C more reliably than one that skips the test. The Energy Saving Trust estimates that airtightness improvements alone can reduce heat loss by 15-25% in a typical semi-detached home. But without testing, you don’t know if the insulation installer left a gap behind the kitchen units. Performance testing turns a guess into a guarantee. For homeowners planning a heat pump, the test is even more critical: a poorly commissioned heat pump can have a COP of 2.0 instead of 3.5, costing £400 more a year to run.
The political reality
Yet the government has not confirmed whether performance testing will be mandatory in the Warm Homes Plan. The consultation closed in March 2025, and officials have not published a response. BSRIA’s intervention is timely, but it faces resistance from installers who argue that testing adds time and cost, and from some housing associations who say it complicates large-scale programmes. The counter-argument is that the Green Homes Grant fiasco of 2020-21, where 90% of vouchers went unclaimed partly due to poor quality assurance, should have taught ministers that speed without verification is false economy. If the Warm Homes Plan repeats that mistake, homeowners will be left with cold homes and higher bills, and the Treasury will have little to show for billions spent.
Households should ask their installer, before signing any contract, whether performance testing is included. If it isn’t, consider paying for a blower door test separately. The £300 cost could save you £2,000 over a decade in avoided heat loss. For those on low incomes, contact your local authority: some are piloting free testing under the Social Housing Decarbonisation Fund. The government’s decision on mandatory testing is expected by November 2025. Until then, the safest retrofit is a tested one.
Frequently Asked Questions
Not yet. The government's consultation on the Warm Homes Plan closed in March 2025, and no decision on mandatory performance testing has been announced. BSRIA is urging ministers to include it before the main spending begins.
A blower door test for a 3-bed semi typically costs £250-£400. Combined with a thermographic survey, expect £400-£700. Some local authorities and ECO4 schemes may subsidise or cover the cost for eligible households.
