Heating work: cost of installation per m² and piece 2026, process and costs

When people are unhappy with their heating, the boiler or the radiators are usually not to blame. What is missing is a calculation. The output of a radiator or an underfloor heating circuit should come from how much heat that particular room loses. That depends on the floor area and ceiling height, how good the windows are, how thick and well insulated the external walls are, and whether the room sits next to a heated space.

A corner room, a north-facing room or a room above an unheated cellar or garage needs more output than an internal room of the same size. If you choose radiators by square metres alone, it often happens in practice that one room stays chilly while the others overheat. The boiler runs longer than it needs to, and your bills go up.

The opposite mistake causes trouble too: a heat source that is too powerful. An oversized boiler keeps switching on and off, never settles into the mode where it runs economically and wears out sooner. If you are putting in new heating or replacing the boiler, it pays to have a heating engineer or designer produce a proper heat loss calculation. And if you are about to insulate the house, the calculation should be based on the house after insulation, not before.

A radiator warms up quickly and reacts quickly when you change the setting. It suits older houses and flats where you cannot raise the floor, and spaces you heat only now and then, such as a holiday home. Fitting is simpler, and a repair does not mean breaking anything open. The downside is that heat spreads less evenly around the room, and the radiator limits where you can put furniture.

Underfloor heating warms the room through the whole floor surface. The heat is spread evenly, there are no warm and cold corners, and you feel just as comfortable at a slightly lower air temperature. It reacts slowly, though, because the whole layer of screed has to warm up first. So it suits steady, continuous heating rather than warming a room quickly for a couple of hours.

Why the water temperature matters

Underfloor heating gets by with cooler water than ordinary radiators, and that makes a real difference to modern heat sources. A condensing boiler runs economically when the water coming back to it has cooled enough for the flue gases to condense inside. A heat pump saves more the cooler the water it has to produce. If you fit a heat pump in an older house and keep the original small radiators, the pump has to make hot water and much of the saving disappears. Larger low-temperature radiators or underfloor heating solve this.

With wet (water-based) underfloor heating, insulation boards go onto the structural floor, an edge strip runs around the walls, then comes a system panel or a film with pipe clips, and the pipes are fixed on top. Everything is covered with screed, which spreads the heat and passes it into the room.

• Screed depth above the pipes: there has to be a minimum layer of screed over the pipes, set by the system manufacturer and the type of screed. For sand and cement screed, roughly 4.5 cm is usually quoted in practice, while anhydrite (calcium sulphate) screed can be thinner. Screed that is too thin cracks, and screed that is too thick reacts even more slowly.
• Movement joints: screed expands as it warms up. The edge strip separates it from the walls, and large or awkwardly shaped areas are divided by movement joints. Where a pipe crosses a joint, it runs through a protective sleeve.
• Circuits: each room gets its own circuit. Long areas are split into several circuits of similar length. Along external walls and under windows, the pipes are laid closer together.
• Manifold: a manifold with flow meters lets you set the flow in each circuit. If you want room-by-room temperature control, electric actuators are fitted to it and wired to room thermostats.

The floor must not get too hot. For living rooms, the European standard for underfloor heating (EN 1264) works with a surface temperature of roughly 29 °C at most, while bathrooms and the edge zones along external walls can be a little warmer. A hot floor is unpleasant underfoot and dries the air. This leads to an important point: in an old, uninsulated house, underfloor heating has limited output and may not be enough on its own.

Heating up the screed and choosing the floor covering

Never dry screed by turning the heating straight up to full. The screed has to cure first. For cement screed this usually takes around three weeks, for anhydrite less. Then comes a gradual heat-up following the manufacturer's protocol: the water temperature is raised in steps, held for a while and then brought down again step by step. Before anyone lays the floor covering, the moisture left in the screed is measured.

Ceramic tiles and stone let heat through well. You can also use vinyl or wood, but the manufacturer must approve them for underfloor heating, and they need to be fully bonded or laid in a way that holds back as little heat as possible. A thick carpet, or a floating floor on a thick underlay, can noticeably reduce what the heating delivers.

Panel radiators are the usual choice. How much heat they give off depends on their height, length and the number of panels and fins. Watch out for one thing: the output in the catalogue applies to a particular water temperature. If the water is cooler, for example with a heat pump, the same radiator gives off much less heat, and you need a bigger one.

Why does a radiator nearly always hang under the window? The warm air rising from it stops the cold draught coming off the glass, and the window mists up less. With modern double or triple glazing this matters less, but the space under the window still makes the most sense. Leave a gap between the radiator and the windowsill, and between the radiator and the floor, so air can flow. Do not cover the radiator with long curtains or push furniture in front of it.

A thermostatic radiator valve (TRV) keeps the room at the temperature you set. When the sun shines in or you are cooking, it turns the output down by itself. The head needs room air flowing around it, though. Tucked under a windowsill behind a heavy curtain, it reads the wrong temperature. When you replace radiators, it is worth replacing the valves too and having the whole system balanced, which means setting it up so the water is shared between all radiators according to what each room needs.

Radiators in a block of flats

In a block of flats with communal heating, the radiators are part of the whole building's system, and many carry heat cost allocators, the small meters that split the heating bill between flats. Before you replace or move a radiator, agree it with the building management or the owners' association. They arrange for the riser to be drained and, after fitting, refilled and bled. The heat cost allocator has to be moved to the new radiator by an authorised company. The new radiator should have a similar output to the old one, otherwise the balance of heating across the building is upset.

A gas condensing boiler is still a common choice in homes with a gas supply. It is not expensive to buy, it is compact and it is reliable. It needs a flue, which often has to be altered when an old boiler is swapped for a condensing one, and a condensate pipe to the drain.

An electric boiler is easy to install. It needs no chimney and no gas supply, and there are no gas safety checks. However, it turns each kilowatt-hour of electricity into roughly one kilowatt-hour of heat, so at typical electricity prices it is more expensive to run. Before installation, check that your main fuse and the supply capacity of your property can handle the load; your electricity supplier or an electrician can tell you.

A heat pump takes heat from the air, the ground or water and, depending on conditions, produces several kilowatt-hours of heat from one kilowatt-hour of electricity. It does well in an insulated house with low-temperature heating. The upfront cost is considerably higher than for a boiler. With an air-to-water heat pump, think about where the outdoor unit will stand, how the neighbours will perceive its noise and where the condensate will drain in winter without freezing. In some places the outdoor unit needs planning permission or has to meet noise limits, so ask your local authority. Many countries offer grants or subsidies for heat pumps, but the conditions change, so check the current rules before you place an order.

Only a qualified, registered gas engineer may connect a gas boiler to the gas supply. Before the boiler goes into use, the gas installation is tested and the flue is checked, and an existing chimney is inspected as well. The first start-up and setting of the boiler are done by the manufacturer's engineer or an authorised service partner. If someone else does it, you may lose the warranty. If you ever smell gas, do not switch anything on or off, open the windows, leave the property and call the gas emergency number for your area, or 112.

The boiler should be placed so an engineer can reach it easily for servicing. If it does not draw its combustion air from outside, the room has to meet the requirements for air supply. Before you change the heat source or alter a chimney, check with your local building authority and the gas network operator which approvals and documents you will need. Rules differ from country to country and sometimes between regions, so do not assume a simple notification is enough. The building authority will tell you exactly what applies.

A new boiler also needs correctly connected hydraulics: a circulation pump, an expansion vessel, a pressure relief valve and, where there are several circuits, a low-loss header. If you combine radiators with underfloor heating, you need a mixing valve so that water that is too hot does not reach the floor.

Over the decades, sludge and rust settle in older pipework. They clog radiators, valves and the boiler's heat exchanger. A new boiler connected to a dirty system can end up with a damaged heat exchanger after only a few years. That is why the whole system is flushed before the new heat source is connected, and a magnetic filter is fitted on the return, the pipe that carries water back to the boiler. It catches metal particles before they get into the boiler.

Manufacturers of both boilers and heat pumps set requirements for the quality of the heating water. After flushing, the system is filled with treated water, and a corrosion inhibitor is added where needed. With old steel pipework, the installer will also assess whether it makes sense to keep it or to replace it with plastic or multilayer pipe.

Is your radiator warm at the bottom and cold at the top, or does it gurgle? There is air in it. In a house, you can bleed radiators and check the pressure yourself. In a block of flats, if the problem is linked to the riser, contact the building management.

1. Switch off the boiler or circulation pump and wait a few minutes so the air rises to the top of the radiators.
2. Put a cloth and a small container under the radiator's bleed valve.
3. Turn the valve slowly anticlockwise with a radiator key until air starts to hiss out.
4. Close the valve as soon as water comes out without bubbles.
5. Work from the radiator nearest the boiler to the one furthest away, and leave radiators on upper floors until last.
6. Check the pressure on the boiler gauge. If it has dropped below the value in the manual, usually around 1 to 1.5 bar in a house, top up slowly through the filling loop while the system is cold.
7. Switch the boiler back on and, once it has warmed up, check that the radiators heat across their whole surface.
8. Call a heating engineer if you need to top up the pressure often, because there is a leak somewhere or the expansion vessel is faulty.

When a contractor hands over new or renovated heating, check that everything works and that you have all the paperwork:

• You have a pressure test record and, for underfloor heating, the screed heat-up protocol
• For a gas boiler, you have the gas installation test report and proof that the flue was checked
• The boiler was commissioned by an authorised service partner and the warranty card is filled in
• All radiators heat across their whole surface and nothing gurgles in the system
• The circuits on the underfloor heating manifold are labelled by room and the flow rates are set
• Thermostatic heads and controls respond when you change the setting
• You have a pipe layout plan or photos of the pipes before screeding, so nobody drills into the floor blindly later on

During the first heating season, keep an eye on the system pressure and the room temperatures. After the first frosts it is normal to fine-tune the flow rates and controls a little. A reliable contractor expects this and allows for it.