Can underfloor heating be your only heat source?
Can underfloor heating heat a room on its own? How much heat a floor gives per m², how much your rooms need, and when you need a second heat source.
It’s one of the first questions people ask us: if I put in underfloor heating, can I take the radiators out? Ask a few installers and you’ll hear yes, no and “it depends”. The last one is right, but it isn’t a dodge. It depends on two numbers, and you can work both out for your own home.
The first is how much heat your room loses on a cold day. The second is how much heat a floor can give off while still being comfortable to stand on. If the floor can give more than the room loses, underfloor heating can be your only heating. If not, it needs some help.
A note on the numbers. Everything below is an estimate based on typical rooms and typical houses. It isn’t a guarantee for yours. Real heat loss depends on your walls, windows, draughts, climate and how warm you like it. For an answer you can rely on, have a professional do a heat loss calculation for each room. We do that for free: send us your floor plan.
How much heat does a room need?
Every heated room is losing heat all the time, through the walls, windows, roof, floor and every gap around a door. The heating’s job is to put it back as fast as it leaves. How fast it leaves depends mostly on how well the house is insulated.
These are the typical figures we use, the same ones behind our running-costs article. They show roughly how much heat a room needs per square metre of floor on a cold day:
| Type of home | Heat needed on a cold day (approx.) |
|---|---|
| Passive house | 30 watts per m² |
| New build | 50 watts per m² |
| Renovated | 75 watts per m² |
| Partly renovated | 100 watts per m² |
| Older home, not renovated | 120 watts per m² |
These are averages. A corner room with two outside walls and a large window needs more than a room in the middle of the house. So do rooms with high ceilings, a lot of glass or an unheated space underneath.
How much heat does underfloor heating give per m²?
This is the part that surprises most people. How much heat a floor gives off isn’t really decided by the heater underneath. It’s decided by how much warmer the floor’s surface is than the room.
As a rule of thumb, a heated floor gives off about 10 to 11 watts per square metre for every degree it’s warmer than the room, rising slightly as the difference grows. (The European standard for floor heating, EN 1264, sets out the exact curve.) In practice:
- a floor at 27 °C in a 20 °C room gives roughly 75 watts per m². That’s about the limit for most wood and laminate floors.
- a floor at 29 °C in a 20 °C room gives roughly 100 watts per m². That’s about the comfort limit for a floor you walk on all day.
So why not just run the floor hotter? Because it stops being pleasant. Above about 29 °C a floor starts to feel hot underfoot after a while, and comfort standards recommend keeping floors where people stand for long periods between roughly 19 and 29 °C. Wood and laminate have their own, lower limit, which we explain in underfloor heating under laminate, vinyl and wood. The exceptions are edge zones along outside walls, where nobody stands for long, and bathrooms, where people are barefoot and like it warmer. Both can run a few degrees higher.
There’s one more thing to allow for. Not all of the floor is heated. The layout leaves out the floor under kitchen units, built-in wardrobes, baths and showers, and heavy furniture covers some of the rest. The room still gets the heat, but it comes from a little less than the full floor area.
When is underfloor heating enough on its own?
Put the two numbers side by side. On a cold day, with the floor at a comfortable temperature and some of it covered by furniture, it looks roughly like this:
| Type of home | Room needs (approx.) | Can the floor heat it alone? |
|---|---|---|
| Passive house | 30 W/m² | Easily, with the floor barely warmer than the room |
| New build | 50 W/m² | Yes, comfortably |
| Renovated | 75 W/m² | Usually, even under wood |
| Partly renovated | 100 W/m² | Often under tile; tight under wood and in cold corner rooms |
| Older home, not renovated | 120 W/m² | Often not on the coldest days |
So in a reasonably well insulated home, underfloor heating can be the only heating. In a poorly insulated one, it will struggle on the coldest days and something else needs to help.
Why a warm floor needs less than the sums suggest
The table above is a little pessimistic, and here’s why. A warm floor doesn’t only heat the air. It warms you directly, and it warms the furniture and walls around you, so they stop drawing heat away from your body. That’s why people in a room with a warm floor usually feel comfortable with the air two or three degrees cooler than in a room heated by warm air. We explain the science in understanding comfort.
A room kept a couple of degrees cooler loses less heat through its walls and windows, so the floor has less to make up. It’s one reason underfloor heating so often turns out to be enough in rooms where the numbers looked tight.
Why the installed wattage is higher than the floor gives off
On our floor heating page you’ll see SafeTech EGS installed at 80 to 220 watts per m². That’s more than a comfortable floor can give off continuously, and it’s deliberate. The extra power brings a cold room up to temperature quickly. Once it’s there, the floor sensor and thermostat keep the surface below its limit, and the heater only switches on as often as it needs to replace the heat the room loses.
What if the floor isn’t enough?
If the numbers don’t add up for a room, there are three sensible options. They’re listed roughly in order of how much they’ll save you over the years:
- Reduce the heat loss. Insulation, better windows and draught-proofing. Every watt the room doesn’t lose is a watt you never pay for, whatever heating you have.
- Add a second warm surface. A heated wall or ceiling alongside the floor shares the load. Walls and ceilings can run warmer than floors because nobody stands on them. See wall or ceiling heating: which should you choose?
- Accept a little extra heat on the coldest days. A floor that does the job for most of the winter, with something else for a few very cold weeks, is a perfectly sensible design.
If you’re still weighing electric floor heating against a water-based system, we compare the two in electric or wet underfloor heating.
The only way to know for sure is a room-by-room heat loss calculation. Send us your floor plan and we’ll do it for you.
Underfloor heating as your only heating: your questions
Can underfloor heating be the only heating in a house?
In a reasonably well insulated house, usually yes. A comfortable floor gives off roughly 75 to 100 watts per square metre, and new and renovated homes typically need 50 to 75. In older, uninsulated homes it may not be enough on the coldest days. These are typical figures; a heat loss calculation for your rooms gives the real answer.
How much heat does underfloor heating give per square metre?
Roughly 10 to 11 watts per square metre for each degree the floor is warmer than the room. A floor at 29 °C in a 20 °C room gives about 100 W/m²; at 27 °C, the usual limit for wood and laminate, about 75 W/m².
Can I remove my radiators if I install underfloor heating?
Often, yes, as long as the floor can cover the room’s heat loss on a cold day. That is usually the case in new and renovated homes. In older, poorly insulated homes, or rooms with a lot of glass, a heated wall or ceiling, better insulation or a little extra heat may be needed. A room-by-room heat loss calculation tells you which.
Why is the installed wattage higher than the heat the floor gives off?
The extra power warms a cold room up quickly. A floor sensor and thermostat then hold the floor surface below its limit, and the heater switches on and off as needed to replace the heat the room loses.
What if underfloor heating is not enough?
Reduce the heat loss with insulation and draught-proofing, add a heated wall or ceiling to share the load, or accept a little extra heat on the very coldest days.
Does underfloor heating work in rooms with high ceilings?
Yes, and often better than warm-air heating. Warm air rises and collects under a high ceiling, while a warm floor heats people and surfaces at the level where people are.
