Underfloor heating and aerothermal heat pumps are widely considered the ideal pairing in the renewable heating world — and it’s not marketing. The physics genuinely lines up. Here’s why they work so well together, and a full walkthrough of what installation actually involves.
Why Heat Pumps and Underfloor Heating Are a Natural Match
A heat pump’s efficiency (COP/SCOP) is directly tied to how hot the water flowing through your heating system needs to be — the lower the flow temperature, the higher the efficiency. Underfloor heating typically only needs 30–35°C water to comfortably heat a room, compared to 55–65°C for standard radiators. That gap translates directly into lower electricity bills and a longer-lasting compressor, since the system doesn’t have to work as hard.
Underfloor heating also releases heat gradually across a large surface area (the entire floor), rather than concentrated at a single radiator, which pairs well with a heat pump’s steadier, longer heating cycles — as opposed to the quick blasts of heat a gas boiler produces.
Step-by-Step: How the Installation Process Works
Step 1: Heat Loss Survey
Before anything is installed, a certified installer calculates your home’s heat loss room by room — factoring in insulation, window size, ceiling height, and local climate. This determines both the heat pump’s required output (in kW) and the underfloor heating layout needed in each room.
Step 2: System Design and Sizing
Based on the heat loss survey, the installer designs:
- The heat pump’s capacity (kW)
- Pipe spacing and layout for each room (tighter spacing in rooms with higher heat loss, like those with large windows)
- Manifold placement (the central hub that distributes water to each underfloor loop)
Step 3: Subfloor Preparation
The existing floor is prepared — this varies significantly depending on whether it’s new construction or a retrofit:
- New build: Insulation boards are laid first to stop heat escaping downward, then the pipe system sits on top before the floor screed is poured.
- Retrofit (existing home): Low-profile underfloor heating systems (sometimes only 15–22mm thick) can often be installed without removing the existing subfloor, though final floor height will rise slightly.
Step 4: Pipe Installation
Flexible PEX (cross-linked polyethylene) pipes are laid in a specific pattern — usually a spiral or serpentine layout — clipped to insulation boards or a pre-grooved panel system, spaced closer together in rooms that lose more heat.
Step 5: Manifold Installation
The manifold — essentially a distribution hub — connects to each underfloor loop and controls water flow to each zone independently. This is also where the heat pump’s circulation pump connects into the underfloor system.
Step 6: Screed or Floor Covering
- New builds: A screed layer is poured over the pipework and left to cure (this can take several weeks before flooring can be laid).
- Retrofits with low-profile systems: Floor covering (tile, engineered wood, or specific heat-pump-compatible flooring) can often be installed more quickly.
Step 7: Heat Pump Installation and Connection
The outdoor heat pump unit is installed and connected to the indoor manifold, buffer tank (if used), and hot water cylinder. Refrigerant and/or water pipework is run and pressure-tested, following the process covered in our [monobloc vs bibloc guide] depending on which configuration is used.
Step 8: Commissioning and Weather Compensation Setup
The installer commissions the system, balances flow rates across each zone, and configures weather compensation — the feature that automatically adjusts water temperature based on outdoor conditions to maximize efficiency.
Step 9: Screed Drying and Gradual Heat-Up (New Builds Only)
For new screed floors, the heating system is brought up to temperature gradually over several days, following a specific heat-up schedule to avoid cracking the screed as it finishes curing.
Retrofit vs New Build: Key Differences
| Factor | New Build | Retrofit |
|---|---|---|
| Floor buildup | Full depth available for insulation + pipes + screed | Limited by existing floor height — needs low-profile systems |
| Installation disruption | None — part of original build | Moderate to significant, room by room |
| Cost | Lower, integrated into overall build cost | Higher, due to floor removal/replacement work |
| Design flexibility | Full flexibility on pipe spacing and layout | Constrained by existing walls, doorways, and floor height |
| Typical timeline | Weeks (part of build schedule) | Days to a few weeks per room/zone |
What Affects the Cost
- Home size — more floor area means more pipe, manifolds, and labor
- New build vs retrofit — retrofits typically cost more due to floor modification
- Number of zones — more independently controlled zones means a larger manifold and more design complexity
- Floor finish — tile conducts heat better than thick carpet, affecting both performance and sometimes flooring costs
- Heat pump size — determined by the heat loss survey, not by underfloor heating alone
Common Mistakes to Avoid
- Skipping the heat loss survey and using rule-of-thumb sizing, leading to an undersized system that can’t heat the home properly on cold days
- Uneven pipe spacing that isn’t adjusted for high-heat-loss rooms (like a room with a large bay window), leaving cold spots
- Poor subfloor insulation, which lets heat escape downward into the ground instead of upward into the room
- Ignoring floor covering compatibility — thick carpet with high tog rating can significantly reduce underfloor heating output
Frequently Asked Questions
Can underfloor heating be added to an existing home without lifting the whole floor?
Yes, low-profile retrofit underfloor heating systems are designed for exactly this, though floor height will rise slightly (often 15–30mm).
How long does a full underfloor heating and heat pump installation take?
For a full-home retrofit, several weeks is typical; for a new build, it’s usually integrated into the standard construction timeline without adding significant time.
Does underfloor heating work well with a high-temperature heat pump too?
Yes, but it’s not necessary — underfloor heating already runs efficiently with a standard heat pump, so pairing it with a high-temperature unit (covered in our [high-temperature heat pump guide]) usually isn’t the most cost-effective combination.
Is underfloor heating enough on its own, or do I still need radiators in some rooms?
Most homes use underfloor heating throughout, but some installers recommend a radiator or towel rail in specific spaces (like bathrooms) for faster heat-up or additional drying capacity.