Homeowners are spending tens of thousands on renovations… only to discover their heating system no longer works for the home they’ve created.
Families planning renovations, extensions and energy-efficient upgrades such as heat pumps are urged to think through their future heating system at the planning stage - not after the builders have finished the job.
Dwellow warns that leaving decisions about radiators, underfloor heating design, pipework and heat pump location until the end of a renovation can lead to costly rework, unnecessary disruption and systems that never work well together or reach peak efficiency.
Dwellow co-founder Ian McLaren explains: “Most people think about flooring, layout and electrics at the planning stage, but forget the heating system. By the time we’re called in, radiators have been sized incorrectly, floors have been laid over the wrong pipe spacing, or we need to rip up beautifully finished rooms to run new pipework.”
The company is highlighting six essential considerations for anyone renovating and installing a heat pump in the near future.
When switching to a heat pump, radiators often need replacing or upsizing because heat pumps work at lower flow temperatures and require a larger surface area (often 2-2.5x bigger) to deliver the same heat as a traditional boiler system.
Being clear from the start of your renovation about which ones need replacing will save ripping out new ones later.
“Builders often fit radiators sized for gas boilers, designed to 55-degree flow temperatures,” McLaren says. “Once the renovation is done and the heat pump goes in, customers very often realise they need bigger ones for high efficiency with a heat pump. It’s not the news we want to break to them.”
Dwellow advises customers to get a room-by-room heat loss survey done before any work begins to establish what radiator upgrades are needed. For unbuilt extensions, this can be worked out using architect plans.
Pairing a heat pump with underfloor heating is a smart choice because both use low-temperature systems, but the correct design is essential. For example, the standard 150ml loop spaces might not be suitable for every room.
McLaren explains: “Different rooms lose heat at different rates, so some need tighter underfloor heating loop spacing to deliver enough warmth. Getting this right not only boosts comfort but also avoids overly complex manifolds with zoning of different rooms, which can hurt heat pump efficiency. Loop spacing and pipe size will be driven by heat loss calculations, so it's best to get these first and then decide the underfloor heating design.”
Flooring is an important consideration with underfloor heating because certain coverings can limit heat output. If the floor covering resists heat too much, your heat pump has to run at a higher flow temperature to compensate, reducing efficiency.
Engineered wood, for example, should not exceed a surface temperature of around 27°C, while thick carpets and underlays can block heat, meaning your system might need to work harder.
“If you choose a floor with temperature limits or thick carpets, but the room has high heat loss, your heat pump simply can’t deliver enough warmth,” says McLaren.
This is why choosing the flooring might be better once you know how much heat the room needs to remain comfortable. Ceramic tiles and stone work particularly well.
Many people forget that as of April 2022 they don’t have to pay VAT when installing a renewable heating system. Dwellow recommends letting heat pump specialists design, supply and install radiators and underfloor heating as part of the complete heating system, so customers can potentially save 20 per cent.
This little renovating perk won’t be around for long though. The zero VAT rate will run until 31 March 2027, unless the government decides to extend it.
McLaren says: “If you upgrade your radiators and add underfloor heating while installing a heat pump or solar panel system, you qualify for 0% VAT. It also applies to insulation upgrades and biomass heating.
‘These generous incentives, alongside the government’s £7,500 heat pump grants, mean it’s arguably the best time to upgrade to renewable energy. Homeowners potentially thousands of pounds and it will also potentially add value to your home.’
A well-designed heating system is essential when installing a heat pump and underfloor heating. While many builders work with excellent plumbers, calculating heat loss, flow rates, pipe diameters and emitter requirements for heat pumps may not be something they have studied.
Dwellow co-founder Adam Raw explains: “People assume that underfloor heating operates at a low flow temperature and, therefore, will work great with a heat pump. However, even underfloor heating can perform poorly if the design isn’t right. The earlier a heating engineer is involved, the better the system will run and the less money you’ll spend on heating”.
The location of your heat pump and cylinder needs careful consideration and the correct sized pipework installed to connect the two. Heat pumps typically require larger pipes than gas boilers, and these should be installed before floors are laid or walls plastered, assuming you want the pipework hidden.
Raw adds: “It’s not always a case of unplugging the boiler and connecting the heat pump to the existing pipework. Different size pipework may well be needed and we often need to run new pipework through renovated spaces. If this isn’t planned early, homeowners (and their builders) may have already laid down new floors or plasterboard. No one wants to be ripping up a newly renovated home they’ve just paid a fortune for.”
He advises talking to a heating designer as early as possible to understand your home’s requirements, save money and avoid rework.
Renovating and considering a heat pump? Dwellow offers a free 30 minute, no obligation consultation with a heat pump design expert at www.dwellow.co.uk.
For a free two-minute heat pump estimate, click on the calculator here.
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