A heat pump runs efficiently at a low flow temperature, so the underfloor heating, radiators or fan coils have to be sized to deliver comfort at that temperature. Whether we are designing a new build from plan, a barn conversion, a refurbishment or an existing home, this is the part of the system that decides whether the heat pump performs. Even if we do not supply or install the emitters, we will work with you to check that what you have chosen will operate at the flow temperature of the heat pump we are installing.
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Partnered with Warmup
17+ years
Sizing Standard
MCS uplift factor
We specify
Stelrad · Warmup · Maxa
VAT On Qualifying Work
Zero-rated to 31 March 2027
An emitter is whatever delivers heat or cool air into the room: a radiator, underfloor heating, a fan coil or a combination of all three. Output depends on the difference between the emitter’s surface and the air around it, so output falls as flow temperature drops. In an existing home that is why a radiator sized for a 70°C boiler delivers roughly half as much heat at the temperature a heat pump runs at. In a new build or conversion there is nothing to inherit and the emitters are specified from the heat loss up.
The fabric of each room and the way it is used determine the size and temperature of each radiator, or the pipe spacing for the underfloor heating coils. How you then control that heat room-by-room or zone-by-zone matters just as much for running cost and comfort. Both Ecoforest and Maxa allow cooling to be designed in alongside the heating. Getting that right – heating and cooling, mixed emitters and zones, all at low temperature – is the whole design challenge, and we approach it room by room.
Heat output depends on surface area and water temperature, so we size every radiator against the room’s calculated heat loss at the design flow temperature. In a new build or conversion that means specifying from scratch. In an existing home it means checking what is already there. Some rooms will need a deeper radiator in the same footprint. Others will be fine as they are.
Where the existing radiators are undersized for a low flow temperature you have three options: change the ones that need it, change nothing and accept a slightly cooler room, or specify a high-temperature heat pump that runs hot enough for the radiators you already have. We do the design work and advise you what each room needs. The decision is yours and choosing not to upgrade does not affect your eligibility for the Boiler Upgrade Scheme.
We carry out the room-by-room calculation using Stelrad Compact radiators with the MCS uplift factor applied, so the specification meets the standard. What you then choose to fit is entirely your decision, by us, or by your own plumber for us to connect onto. It doesn’t affect your grant eligibility. Where there’s existing pipework, we drain and clean the system before connecting it.
Underfloor heating can run at the lowest flow temperature of any emitter and that is where a heat pump performs best. It heats from the floor upwards rather than pushing warm air to the ceiling, which suits open plan, double height rooms in barn conversions and new builds particularly well. It can also provide gentle cooling where the floor surface is kept above dew point.
What decides whether it performs is pipe spacing. Closer centres put more pipe into each square metre, meaning more output at a lower flow temperature, and the spacing is varied within a room, tightened under glazing and around perimeters where heat loss is greatest.
We’ve worked with Warmup for 17+ years on exactly this: a CAD layout drawn room by room, with their thermostatic controls hardwired into the system so that zone demand reaches the heat pump directly rather than depending on a wireless link. Our default recommendation whenever floors are being laid or replaced – new builds, barn conversions or refurbishments. Low profile systems also make it a genuine option for existing homes where floor build-up is limited.
Air moved across a coil. Compact, high output for their size, quick to respond, and the only emitter that cools properly, because they manage the condensation that cooling produces. The right choice for heavily glazed and south-facing rooms. Fan coils come in a range of formats: wall-hung high, low, or hidden behind grilles. With the Maxa Grimper range, heating and cooling can be achieved from the same unit, and they’re slimmer with a more contemporary look than a radiator.
Most well-designed systems use more than one emitter type. Underfloor downstairs in an open-plan living area, correctly sized radiators upstairs, fan coils where cooling matters, each zone controlled independently.
Radiators
A UK manufacturer with a wide range of panel sizes and depths, including outputs suited to low temperature radiator design for heat pumps. Depth rather than length is usually what recovers the output needed, keeping radiators within the wall space a room already has.
Underfloor Heating
Covers both in-screed systems for floors being laid or replaced and low-profile systems that go over an existing floor, so underfloor heating is a genuine retrofit option, not something reserved for new build. CAD pipe layout produced room by room, with hardwired thermostatic controls.
Fan Coils
Heating and cooling from the same unit, with proper condensate management, sized against each room’s cooling as well as heating load.
Emitters aren’t funded separately by the Boiler Upgrade Scheme. Where they form part of a qualifying MCS-certified heat pump installation, they fall within the scope of the works and are zero-rated for VAT until 31 March 2027.
Boiler Upgrade Scheme grant towards an air or ground source heat pump, plus 0% VAT on qualifying work.
Rarely all of them. The question is asked room by room: at the design flow temperature, does this radiator still meet this room’s calculated heat loss? For a fair proportion of rooms the answer is yes. We measure it during the survey and tell you which need changing before you commit.
Yes, and most well-designed systems do. Underfloor downstairs where floors are accessible, radiators upstairs, fan coils where a room needs cooling. Each becomes its own zone with its own control, which is what lets the system suit how you actually live in the house.
No. There’s nowhere for condensation to go, and convection doesn’t work in reverse. Underfloor heating can take the edge off a warm day, provided the floor surface stays above dew point (doesn’t drop below the point where condensation can collect). Fan coils are the only emitter that cools properly, because they manage condensate.
It responds more slowly than a radiator, which is a feature rather than a fault. A heat pump is designed to run gently and continuously at a low flow temperature, and underfloor heating holds that steady warmth well. It suits a system that isn’t being switched on and off.
A fan coil moves air across a heated or chilled coil. They’re compact, deliver high output for their size, respond quickly, and are the only emitter that cools properly. We specify them in heavily glazed and south-facing rooms, and anywhere cooling matters as much as heat.
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Whether your existing emitters can stay, need upgrading, or a different approach entirely suits the room better, we’ll tell you properly rather than guess.
Prefer to talk it through first?
We design renewable heating systes around your home and the way you live.
Prefer to talk to us first?
Call: 01271 850 040
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Prefer to talk to us first?
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