For years, we’ve heard a consistent refrain from homeowners on the Renewable Heating Hub forums and YouTube comments: “I’d happily switch to a heat pump… if only it didn’t wreck the house.” The UK’s decarbonisation narrative often spotlights clever compressors, smart controls and ambitious targets. But inside British homes, the real choke point is far more prosaic.
It’s the radiators.
Across the UK, 25 million homes rely on legacy radiator systems, designed for high-temperature boilers rather than low-temperature heat pumps. Retrofitting typically demands radiators 30-50% larger, a prospect that homeowners often find unappealing or impractical. No surprise, then, that according to industry data, over 80% of heat pump retrofits are cancelled or refused because of perceived disruption, cost or loss of space. That’s a staggering number!
We see this every day in comments, DMs and emails: people are interested in heat pumps (even enthusiastic) but balk at having to upend rooms, tear up flooring or fit radiators the size of surfboards. And installers tell us the same story from the other side.
As Ethan Wadsworth, Director at DiscreteHeat, puts it: “Heat pump retrofits are often sold on efficiency, but delivered with compromises. Most homes are only 100-500 watts per room short on their emitter capacity, but to bridge that small gap, we end up replacing perfectly good radiators, redesigning whole systems and creating disruption no one wants.”
This is the main frustration behind the UK’s retrofit bottleneck. Installers know that low flow temperatures are essential for achieving strong COPs, yet the pathway to get there nearly always involves upheaval. Larger radiators require two-person lifts, old units are scrapped unnecessarily and every seemingly simple job morphs into a redesign exercise often requiring floors being lifted and pipes being moved.
But what if most homes aren’t actually as incompatible with heat pumps as we assume?
When DiscreteHeat analysed years of their own heat-loss data, they found something surprising: “Over 80% of existing radiators were within about 30% of the required output for low-temperature systems,” Wadsworth told us. “Once we saw that, it became clear that full-scale radiator replacement is often unnecessary. We don’t need to tear out what’s there, we just need to supplement it.”
This insight led to the development of Add2Rad, not as a product but as a methodology, a systematic, minimal-disruption approach to strengthening emitter capacity using small, strategic additions rather than wholesale change.
“For customers that want to eliminate radiators completely, the ThermaSkirt still provides that option. But the Add2Rad approach will be the fastest, least disruptive and often lowest cost way to make an existing properties emitters optimised for heat pumps”
Add2Rad connects a short run of ThermaSkirt aluminium skirting heating in series with the existing radiator. A simple tee off the flow pipe before the TRV allows the ThermaSkirt profile to act as an extension of the radiator, boosting its output at low temperatures without altering the radiator itself.
In practice, 2-4 metres of discreet aluminium skirting typically supplies the missing wattage.
Having looked at the tech specs and product offering, the advantages, from both homeowner and installer perspectives, are hard to ignore:
- Existing radiators remain in place, maintaining the look and feel of rooms.
- Existing pipework is retained, avoiding the need to chase walls or lift floors.
- Floor coverings stay undisturbed which is a major win for homeowners.
- Waste is avoided, because working radiators are supplemented, not scrapped and sent to landfill.
- One-person installation is common, speeding up turnaround and reducing costs.
- Homes can often be made heat-pump-ready in a single day.
“We wanted something non-invasive,” Wadsworth says. “A way to give the radiator that extra 30% it needs without asking people to redesign their homes. Add2Rad makes the most of what’s already there and that’s why it works.”
From our vantage point at Renewable Heating Hub, where we engage daily with both homeowners and heating engineers, this methodology speaks directly to one of the biggest blockers in the heat-pump conversation. The technology is sound. The will is there. But the domestic realities (space, aesthetics, disruption) have too often been ignored.
By reframing the emitter challenge not as a demolition project but as a light-touch upgrade, Add2Rad suggests a way forward that acknowledges the constraints of British homes rather than bulldozing through them.
It won’t remove the need for proper heat-loss calculations, nor does it eliminate the need for thoughtful system design. But it does offer something we believe is increasingly essential: a practical, efficient and homeowner-friendly pathway to low-temperature heating.
And if the UK is serious about scaling heat pumps, solutions like this may prove every bit as important as the technologies they support.
You can find out more about ThermaSkirt and Add2Rad here.
One of those brilliant ideas that is obvious with hindsight. 😎
A few weeks ago, I was having a discussion with someone about better (more effective?) operation of energy-hungry resources and, in particular, the possibility of making use of the heat generated from datacentres – possibly for community heating. The problem there, of course, was how to get the heat from a big old datacentre out in the middle of nowhere to a conurbation that’d want it. Then, a couple of days ago, I read a news article about a company installing small datacentre units (chest freezer-sized) in people’s sheds/homes with the view of reducing the homeowners’ heating bills. It seems the people the journalists were talking with saw their monthly heating bills drop from around £375 to about £40. Obviously, this is still relatively experimental but is a wonderful example of innovation turning things on their head; if we can’t move Mohammed to the mountain, how about a bit of Pyrenees-shifting rock by rock?
This Add2rad concept seems to be another example of a bit of lateral thinking to solve a problem by chopping it into smaller chunks. The recently-discussed Heat Geek “zero disrupt" approach alongside their standard approach is certainly an attempt to break the deadlock but the choice feels like a binary “ideal and expensive" vs “cheap with compromises" whereas the idea of supplementing the existing radiators looks at first glance as a combination of minimising both disruption and compromise.
Despite the very public criticising of heat pumps (legitimate and not), the technology is now mainstream in the public’s eyes – even the public that choose to reject it. As a result, these innovations are now what I would regard as second generation and I’m quite excited to see what I’m sure will be a number of others following on.
Oh, and it seems to me that the Thermaskirt product could represent a relatively low cost way for homeowners who’ve been shafted by cowboys underspeccing radiators to get a practical fix.
Super niche. Bigger rad is less labour, less connections, less upheaval, and less money.
Yes, I was just talking to a heatpump manufacturer, so much excitement about details on efficiency, buffer tanks, etc, multi zone. Even after explaining that we wanted as little disruption as poss., it took a couple of iterations to settle.
We just want something simple. No probs to have a rad replaced for a larger one or double layer. Like that, there’s less chance that anything breaking needs to be fixed.
The idea (and at least one similar product) has been around for a while, I even considered it for one awkward room when I did my upgrade a year ago.
However the output per linear metre simply didn’t add enough in my case unless I went all around the room which wasn’t realistically possible due to doorways. I suspect such practical problems will frustrate it’s use in many cases and as @dtard says larger rads are cheap and easy to install. However the more options the better, with 20m houses to do in in the UK alone even a tiny percentage may be a worthwhile market.
Another issue is the insulation of British Homes by the builders. Some cut corners to save money, because there is no penalty, nor will a new buyer start tearing furniture and drilling into the walls.
Our property is a new build, but the cavity wall insulation is lacking. I had someone come over to check it, and they put a camera in different locations, I could see huge gaps. In addition, behind every covered surface, such as furniture etc, there are gaps where cold air is coming through when it is windy outside. Not only that, but cold air comes through the different extractor fans exhausts. So our house has so many cold air entry points, it is crazy, then add the window trickle vents and you have 0 air tightness.
I was quoted £4000 to remove the old insulation, and £5500 to add the new one.
The only way forward, is to actually build houses with Heat Pumps in mind, in the first place, including underfloor heating.
Your situation is unacceptable (imho) and your house doesn’t meet building regs. Have you told your builder you want it fixed on his snagging list or have they gone bust and can you get it fixed on the NFHB(?) guarantee?
Clearly you house hasn’t got the air-tightness barriers fitted well either!
It’s not a heat pump issue but a building industry one
@DREI
My guess is that the people that you had coming over are building the evidence pack, right? 😉
If it is combined with the BUS and they make it all good, it could be a way to replace tired skirting..
The dream would be if someone like Octopus would take care of it…