Grosvenor backs Aeroseal – what it means for home retrofits

Nearly a third of heat lost from the average UK home escapes through gaps in the fabric – cracks around skirting boards, pipe penetrations, and poorly sealed loft hatches. The typical 3-bed semi loses enough warm air each winter to fill 20 double-decker buses. Until now, fixing those leaks meant invasive work: stripping out plasterboard, lifting floorboards, or paying for expensive blower-door tests followed by painstaking manual caulking.

That calculus may be shifting. As reported by BusinessGreen, the Grosvenor estate – one of Britain’s largest landowners – has invested an undisclosed sum in Aeroseal, a US company whose aerosol-based system seals building envelopes from the inside. The technology, already deployed in social housing schemes in the UK, uses a non-toxic polymer mist that is blown through a building’s ventilation system. The particles bond at the edges of cracks and gaps, forming a flexible airtight seal. Early trials suggest the process can reduce air leakage by 80–90% in a single day, with no disruption to occupants.

Who qualifies – and who doesn’t

Aeroseal is not yet a household name, and it is not available through every local installer. The UK distributor, a firm called EnviroVent, has focused on the social housing sector so far – housing associations in Leeds and the Midlands have used it to bring older stock up to the Decent Homes Standard. For owner-occupiers, the picture is patchy. A handful of retrofit coordination services, including the government’s Green Homes Grant Local Authority Delivery scheme, have funded Aeroseal treatments in specific postcodes. Outside those areas, homeowners would need to pay privately – and the cost is not trivial. Industry sources indicate a typical semi-detached house costs between £1,500 and £2,500 to treat, depending on size and number of rooms.

The catch is that Aeroseal addresses only air permeability, not thermal bridging or condensation risk. A home that is too airtight without adequate mechanical ventilation can suffer from mould and poor indoor air quality. The company recommends a whole-house approach: seal first, then install controlled ventilation. For homeowners already planning a heat pump or solar PV installation, an Aeroseal treatment could reduce the required heat pump capacity by 10–15%, lowering upfront costs and improving seasonal efficiency.

What it costs a typical 3-bed semi

To put the numbers in context: a typical 1930s semi-detached house in the UK has an air permeability of around 10–12 m³/h·m² at 50 Pa. Building Regulations for new homes require a figure of 8 or lower. Aeroseal can bring an existing leaky home down to 3–5 m³/h·m² – better than most new builds. The energy saving depends on the starting point, but the Energy Saving Trust estimates that reducing air leakage by 50% in a gas-heated home saves roughly £80–£120 per year. An 80% reduction, as Aeroseal claims, could push that figure to £200–£400 annually, depending on floor area and heating system. Against a treatment cost of £2,000, the simple payback is 5–10 years – comparable to cavity wall insulation, but with less disruption.

Yet the real value may lie in EPC improvement. An airtightness upgrade can shift a property from EPC band D to C, or from C to B, depending on other factors. That matters because from 2025, landlords will need a minimum EPC rating of C for new tenancies. For owner-occupiers, a higher EPC can add £5,000–£10,000 to a property’s sale price, according to research from Nationwide. Grosvenor’s investment suggests the estate sees this as a long-term asset value play, not just a compliance cost.

What this misses – and what comes next

But the technology is not a silver bullet. Aeroseal has not yet been certified under the British Board of Agrément’s scheme, though it holds European Technical Assessments. Some insurers and warranty providers may not recognise the treatment without a separate air test. And the UK’s retrofit industry is still fragmented: there is no single accreditation for Aeroseal installers, and the company’s training programme is only now expanding beyond a handful of firms.

What Grosvenor’s backing does signal is that deep-pocketed institutional investors are betting on retrofit as a mainstream market. If the technology scales, costs could fall by 30–40% within three years. That makes it affordable for the mass market. For now, homeowners interested in the treatment should ask their local retrofit coordinator or search the National Insulation Association’s directory for certified airtightness specialists. The window for grant funding may be narrow – the government’s Boiler Upgrade Scheme does not cover airtightness, but the new Great British Insulation Scheme, launching in early 2024, could include it as a qualifying measure.

Households on standard variable tariffs can check eligibility through the Energy Saving Trust’s home energy check tool. Installation slots for Aeroseal are currently limited to a few regions, but EnviroVent expects to double its network of trained installers by mid-2024. If you are planning a heat pump or solar installation, ask your installer whether an airtightness assessment and treatment should come first – it could save you hundreds on both the installation and your annual bill.