Insulation manufacturer SuperFOIL has published a reaction piece to the Government's retrofit plans, pegging its comments to the run of intense UK heatwaves that show no sign of easing. It is not the only company in the insulation sector making noise about retrofit policy right now, and the underlying picture is worth unpacking properly.
Retrofit work has been a growing revenue stream for many UK builders and insulation installers over the past three years. Policy changes are about to shape what that work looks like, how it gets funded, and what "compliant" insulation means on a practical job.
What the UK Government's retrofit plans actually are
There are two main policy frameworks running in parallel, and it is easy to conflate them.
The Future Homes Standard applies to new builds in England. It sets out that homes built from 2025 onwards must be significantly lower carbon than those built under the previous Part L requirements. Boilers will not be installed in new homes from the late 2020s under this pathway, and the fabric of new builds must perform well enough that heat pumps are the primary heating technology. For insulation, that means wall, floor and roof U-values (a measure of how well a structure resists heat passing through it) are higher than before. A lower U-value is better: less heat escaping in winter, less heat entering in summer.
The Warm Homes Plan is the retrofit side. The Government has committed to upgrading existing homes to at least EPC band C by 2030. EPC stands for Energy Performance Certificate, a rating from A (most efficient) to G (least efficient). Most of the UK housing stock sits between D and G. Getting homes to C means adding insulation, improving airtightness, and often replacing heating systems. The funding mechanism being built out includes Great British Insulation Scheme grants, ECO4 funding routed through energy suppliers, and area-based schemes delivered through local authorities.
There is a third strand that SuperFOIL is specifically raising: summer overheating. Until recently, retrofit policy was written almost entirely around winter heat loss. Insulate better, heat less, use less gas. But a house that is well sealed and insulated in a wall and roof system that does not manage solar gain will also trap heat in summer, sometimes making overheating worse. The insulation industry is starting to push back on a framework that does not distinguish between insulation products that manage summer heat as well as winter heat loss.
Why summer overheating matters for what you specify
This is where it gets practical. Not all insulation performs the same way in summer heat.
Mineral wool (rock wool and glass wool) is effective at slowing heat transfer, but it does not have high thermal mass and does not perform differently between summer and winter. It holds heat in or out based on the temperature differential.
Multifoil insulation, the category that includes SuperFOIL's products, combines multiple layers of reflective foil and wadding. The reflective layers bounce radiant heat away. In summer, that means a multifoil installed in a roof or wall can reflect solar radiation away from the building rather than conducting it inwards. In winter, it reflects internal warmth back inward. The performance claim is that multifoil systems offer year-round benefit beyond what a straight mineral wool layer provides.
This is not to say one product category is universally better. U-value calculation methodology for multifoil products has been a point of industry debate for some years, and some installers prefer to stick with products whose calculations are based on established BS EN standards. The point is that if retrofit policy starts requiring installers to demonstrate summer overheating performance alongside winter heat loss, the specification conversation will change, and the products you reach for may change with it.
What types of retrofit work are on offer for tradespeople right now
Retrofit is not one job. Here is what the current funded landscape looks like for UK installers:
Loft insulation top-ups. The quickest and cheapest retrofit measure. Most ECO4 and GBIS work starts here because the payback is fast and the disruption is minimal. Blown-in mineral wool or loose fill into an empty loft, or rolling in batts to bring the depth up to 270mm or more.
Cavity wall insulation. Where the property has an unfilled cavity (common in homes built between 1930 and 1995), blown insulation fill is a funded measure. Not suitable for properties with persistent damp issues in the cavity; always survey before quoting.
External wall insulation (EWI). For solid-wall properties (pre-1920s homes, system-built concrete properties) where there is no cavity to fill. EWI fixes insulation boards and a render system to the outside of the wall. It is significantly more expensive and more disruptive than cavity work, but it is the primary funded measure for solid-wall homes under GBIS and local authority schemes.
Roof insulation in occupied outbuildings and extensions. Multifoil products are commonly used here because they can achieve required U-values in thinner build-ups than mineral wool, which matters where rafter depth is limited.
Internal wall insulation (IWI). Less common because it reduces floor area and requires all skirtings, window reveals, and electrical outlets to be moved, but used in solid-wall properties where EWI is not possible (listed buildings, flats).
What trades should be doing now
The policy direction is towards higher standards and more funding availability, but the timing and exact requirements are still moving. Here is the practical checklist:
Check your PAS 2035 awareness. PAS 2035 is the publicly available specification for retrofit work, and ECO4 and GBIS jobs require that the work is designed by a Retrofit Assessor and coordinated by a Retrofit Coordinator. If you want to be a direct funded contractor, you or your firm need to be working within this framework. The TrustMark scheme is the Government's quality assurance route for retrofit work.
Know your U-value targets. The Warm Homes Plan and GBIS have minimum performance requirements for each measure. These are expressed as post-installation U-values. Make sure the products you're specifying, and the installation depth you're achieving, hit those targets rather than just filling the cavity or loft and hoping the paperwork sorts itself out.
Get familiar with EPC assessment. Being able to read and interpret an EPC helps you identify the highest-value measures on any given property. The assessor has already done the survey; the EPC tells you the baseline and what the likely improvement from each measure would be.
Watch the overheating risk conversation. If the Government consultation on summer overheating feeds through into updated guidance under the Future Homes Standard or Warm Homes Plan, the specification standards for insulation products in retrofit may shift. Follow updates from the CIBSE (Chartered Institution of Building Services Engineers), whose TM59 methodology covers overheating assessment in dwellings.