Why underfloor heating makes sense in a renovation

Underfloor heating (UFH) has a reputation as a new-build luxury, but it is often a brilliant fit for renovation projects. You are already lifting floors, moving radiators, and rethinking how your home is heated. Installing UFH now can free up wall space, deliver gentle, even warmth, and future-proof your property for a heat pump. The key is to plan around the constraints of an existing house rather than treating it like a blank canvas. With careful attention to floor build-up, insulation and controls, you can enjoy comfortable underfloor heating without runaway costs.

Check your floor build-up and headroom first

Before you fall in love with a particular system, measure the available height. In a renovation, every millimetre matters — especially at door thresholds and under kitchen units. Traditional wet UFH in a new build sits in 65–75mm of screed, which is rarely practical in a retrofit. Low-profile systems have changed the game.

For suspended timber floors, fit insulation and pipes between the joists, then overlay with a thin structural deck. For solid floors, excavate to create a new insulated slab, or use an overlay system just 15–20mm thick. If your renovation includes a rear extension on a sloped garden, a new insulated slab is the perfect place to run UFH from the start. Check that your chosen build-up does not raise the floor so much that doors need trimming.

• Measure from the top of the joists or slab to the finished floor level.
• Allow for floor finish: tiles add 10–15mm, engineered wood 15–20mm.
• Keep pipes away from areas under kitchen units and heavy fixtures.
• Consider door thresholds and any level changes between rooms.

Insulation is non-negotiable

Underfloor heating works best at low flow temperatures — typically 35–45°C, compared with 70–80°C for radiators. That efficiency is only possible if heat goes up into the room, not down into the ground. Insulation is therefore the single most important factor in keeping running costs manageable.

For a suspended timber floor, fit rigid PIR insulation between the joists, aiming for at least 100mm where possible, and seal gaps to prevent draughts. For a solid floor, place 50–100mm of PIR beneath the screed or overlay, with a suitable vapour barrier. In older properties, avoid trapping moisture against original stone or brick. Building Regulations Part L sets minimum U-values for floors, but exceeding them is wise if you want low bills. A well-insulated floor also means your boiler or heat pump can run at lower temperatures.

Wet or electric? Choose the right system for your renovation

There are two main families of UFH: wet (hydronic) and electric. Wet systems circulate warm water from a boiler or heat pump through pipes, usually connected to a manifold with separate zones. They are ideal for whole-house renovations and heat pump systems. Electric systems use cables or mats; they are simpler to install but cost more per kWh of heat.

For a renovation, a low-profile wet system is often the best balance. It can be laid over an existing solid floor or between joists, and it integrates with your existing heating controls. Electric mats make sense for small, occasionally used areas such as an ensuite or a downstairs cloakroom. A hybrid approach — wet UFH in the main living areas, electric in a small bathroom — can be a pragmatic compromise.

• Wet: lower running costs, works beautifully with heat pumps, needs manifold and pump space.
• Electric: minimal build-up, higher running costs, best for small rooms.
• Hybrid: combine both to suit how you use each space.

Controls, zoning and running costs

Even the best-insulated UFH will waste money if it is controlled poorly. Zoning is your friend: divide the house into areas you use at different times. Each zone gets its own thermostat and actuator on the manifold, so you only heat the rooms you need. Smart controls can learn your routine, and weather compensation adjusts the flow temperature based on outside conditions.

Remember that underfloor heating responds slowly. Use programmable schedules with gentle set-backs rather than big temperature swings. Set the flow temperature as low as comfortably possible — often 35–40°C is enough for well-insulated rooms. Avoid overheating: every degree above 20°C adds roughly 5–10% to your heating bill.

Practical installation tips and floor finishes

Installation follows a logical sequence: insulate, lay the pipes or mats, pressure-test, then cover with screed or an overlay panel. Never skip the pressure test — it is much easier to fix a leak before the floor finish goes down. Commission gradually: start low and increase over several days to avoid thermal shock.

Your choice of floor finish matters. Tiles are excellent conductors and work beautifully with UFH. Engineered wood and luxury vinyl tiles (LVT) are also suitable if they are marked as compatible. Solid wood can move and crack, and thick carpets act as insulation, forcing the system to work harder. Always check the thermal resistance (tog value) of underlay and carpet — aim for a combined tog of no more than 2.5. If your renovation involves a sloped garden and differing floor levels, UFH can help create a seamless transition. Plan ahead, insulate well, and control each zone wisely — then underfloor heating will reward you with quiet, even warmth for years to come.