Is your underfloor heating messing with your heat pump? This might be why

As more homeowners embrace low-carbon heating, thousands are upgrading to heat pumps paired with underfloor heating. But while these systems promise long-term efficiency, many households are left scratching their heads over unexpectedly high running costs. 

According to home energy specialists at Dwellow, the culprit may be hiding in plain sight. Heat pump expert and Dwellow co-founder Ian McLaren explains that the problem often comes down to how underfloor heating systems are configured, specifically, zoning individual rooms with thermostats and manifold actuators that control water flow. This setup causes rooms to switch on and off frequently to maintain temperature, which works well with boilers. Heat pumps, however, perform best when they can heat a large volume of water steadily rather than constantly cycling on and off.

“People often assume the heat pump is the problem, but it’s usually the underfloor heating setup,” McLaren says. “Zoned rooms and multiple thermostats are what really undermine heat pump efficiency. A heat pump uses the most energy when its compressor starts up, and that happens more often when there isn’t enough water volume to heat because not all zones are open. We see this configuration a lot, and the usual fix is adding a buffer tank, although that isn’t always necessary either. In reality, most systems don’t need zoning or a buffer at all.”

With traditional gas boilers, dividing a home into multiple heating zones can make sense. You can heat certain rooms, turn others down, and save energy and the efficiency is less of a concern given the relative cost of gas. 

Heat pumps work differently. They deliver low, steady, continuous heat. When zones turn on and off, or when multiple thermostats constantly call for heat at different times, the heat pump is forced to ramp up and down repeatedly. The result?

• Short cycling
• Reduced efficiency
• Higher running costs
• Premature wear on equipment

So what can be done about it?

“People are often surprised that the most efficient setup is actually the simplest,” McLaren explains. “Tell your engineer to remove the buffer if your design includes one, take the actuators off the manifold, and let the underfloor heating run in an open loop. That allows the heat pump to operate exactly as intended, delivering steady, efficient heat throughout your home. This is what truly unlocks the performance you were promised.”

Dwellow’s top tips for fixing issues with underfloor heating and heat pumps:

1. Avoid a buffer tank

Many traditional installations, new builds and large home renovations include a buffer because it makes zoning possible. But heat pumps rarely need this equipment and removing it helps the system run more smoothly and efficiently. 

2. Get rid of the actuators on the manifold

Actuators open and close underfloor heating loops based on room thermostats, much like the thermostatic valves on a radiator. But these constant stop-start signals are exactly what undermine a heat pump’s performance. Removing the actuators allows the system to run at a steady, optimised temperature. Instead of shutting loops off entirely, the heat pump simply adjusts the water temperature to maintain comfort.

3. Run the underfloor heating “open loop”

Instead of constantly turning zones on and off, an open-loop underfloor heating system circulates warm water continuously at low temperatures. In this setup, the underfloor heating manifold essentially acts as one large, gentle radiator.

Are you thinking of renovating? Here are Dwellow’s expert advice

If you’re planning a renovation, extension, or a whole-home heating upgrade, keep these points in mind before installing underfloor heating with a heat pump:

• Avoid complicated multi-zone setups because what works for boilers can seriously disrupt heat pump performance.
• Choose installers who truly understand heat pump design and low-temperature systems.
• Ask for low-flow, continuous-circulation underfloor heating without buffers or actuators.
• Use a single, weather-compensated control system rather than multiple room thermostats competing with one another.
• Depending on the size of your property, you may not need the secondary pump on the manifold; and if you have full underfloor heating or correctly sized radiators, you likely won’t need a blending valve either.
• Ensure your home is well insulated so the system can run efficiently at low temperatures.
  

About dwellow

dwellow is a leading UK-based home energy specialist offering nationwide installation of heat pumps, solar panels, and battery storage. With decades of combined industry experience, they support homeowners in making the switch to renewables and accessing government grants. They are accredited by the MCS, TrustMark, HIES, and Which. 

Contact
Emily Allen 07468 416945
emily@dwellow.co.uk
www.dwellow.co.uk