Wales has the oldest housing stock in the UK. Around a third of Welsh homes went up before 1919, well before anyone gave a second thought to thermal performance or energy ratings. That means a lot of stone walls, solid floors, single-glazed windows and heating bills that hurt.
But the Welsh Government hasn’t written these homes off. Instead, it’s poured money into one of Britain’s most ambitious retrofit programmes. So what does that actually mean if you own one of these properties, and what should you know before the work starts?
What the Welsh Government Is Funding
The Optimised Retrofit Programme (ORP) has been running since 2020 and has now pulled in over £466 million in total funding. In January 2026, another £99 million was confirmed for the 2026-27 round. More than 31,000 social homes across Wales have already had energy efficiency upgrades.
The work usually covers external wall insulation, window replacements, heat pump installations and better ventilation. The programme follows a “fabric first” approach, which basically means fixing the building envelope before touching the heating system. That’s especially important in older Welsh homes, where damp stone walls and lime mortar don’t always play nicely with off-the-shelf insulation products.
The Challenges of Retrofit in Older Welsh Homes
Retrofitting a Victorian terrace in the Valleys or a stone cottage in Gwynedd is a completely different job to insulating a 1970s semi. Older Welsh properties tend to have solid walls with no cavity to fill, and plenty of them sit in conservation areas or carry listed status. That can seriously limit what you’re allowed to do on the outside without planning approval.
Then there’s the issue of breathability. Traditional lime mortar lets moisture move through the wall naturally. Seal it up with the wrong insulation and you’ll trap damp inside, which will cause more damage than it prevents. Getting the specification right takes proper expertise, and not every installer has experience with heritage construction.
How Retrofit Affects Your Home Insurance
This is the part most people don’t think about until it’s too late. Retrofit work can change your home’s construction type, rebuild cost and risk profile all at once. Adding external wall insulation, for example, might reclassify your property as non-standard construction. Fitting a heat pump or carrying out structural alterations during the project could also affect your cover.
If you own an older Welsh property, specialist home insurance cover is often needed both during and after retrofit work. Standard policies don’t always account for listed buildings, non-standard materials or homes that are mid-renovation. And if your insurer doesn’t know about the changes you’ve made, you could end up with a rejected claim when you need it most.
Don’t Let the Paperwork Fall Behind the Build
Wales is doing something genuinely impressive with its retrofit programme, and private homeowners are starting to follow the lead set by social housing. But before you book a contractor, check your insurance.
Make sure your policy reflects what your home looks like now and what it’ll look like once the work’s done. A quick call to your insurer before the scaffolding goes up will save you a lot of hassle later on.