How It Works

Underfloor heating is becoming increasingly popular in New Zealand as a means of having a constantly heated home and a way of improving your living space.

How does underfloor heating work?

Underfloor heating systems can be run using most heating fuels. Underfloor heating provides a mix of radiated and convection heat creating a comfortable and constant temperature between the floor and ceiling.

Underfloor heating systems are located under your floors. Unlike radiator central heating which encroaches on your space in your rooms and determines where you can place furniture, underfloor heating has no impact to your space.

With the push towards using renewable energy for heat sources underfloor heating systems can be run a variety of ways. A conventional gas, oil or solid fuel boiler can be used with a ‘wet’ system. Heat pumps are more efficient at the lower temperatures at which underfloor heating systems operate. Underfloor heating systems do not need to be run at high temperatures as they warm a large area and heat can be lost unnecessarily. A biomass boiler could be used and the system may even be supplemented by a solar thermal panel. Underfloor heating can also be powered using electricity.

“Wet” Underfloor Heating

Using reinforced polythene piping heated water is circulated along circuits. There are separate circuits for different rooms and areas. Each circuit gets connected to a manifold and has regulating valves and a thermostat. This allows different rooms to be heated to different temperatures and at different times, minimising unnecessary energy use.

The manifolds distribute water at temperatures of 35-60ºC which in turn heats the floor to a comfortable setting of between 18-29oC. When the room reaches a pre-set temperature the thermostat signals to a valve on the manifold to close the circuit in that room.

There are three main types of wet underfloor heating:

1) Solid floors
This is the common choice for new build properties. The underfloor heating is permanent as it is built into concrete or screed floors. Insulation is laid first, and then the pipes are put down in a specific pattern before the concrete or screed is poured. Many types of floor finish can then be overlaid including wood, stone, tiles, vinyl or carpet, though careful consideration is needed to ensure it will not be affected by the heat and/or will not insulate against it.

2) Suspended floors
The underfloor heating system is inserted between the joists or battens in the suspended floor, with suitable insulation below. The casing usually consists of a tongue and groove floor board. This allows a range of floor coverings to be fitted, with the same considerations as above.

3) Floating floors
This is the quickest and easiest type of underfloor heating to install as there is no requirement for screed or concrete to set. This system is ideal for retrofitting into existing homes as it can be used above an existing solid or wooden floor. The pipes are inserted into preformed heat plates which rest in grooves in the insulation. You may find though that your floor levels are raised significantly in order to fit the system in.

Electric underfloor heating

Electric underfloor heating uses wires that heat up when electricity is provided. In new builds a screed finish is usually used and for existing builds electric matting or tiles are used.

Electric underfloor heating is often used with retrofitted underfloor heating as it is easier to install than water pipes. It is also likely to be more responsive than wet systems so will warm up a room quicker. The cost of using electricity does need to be considered as it is considerably more expensive as a heating fuel than gas so you will need to factor this into your budget.

Radiator Heating

Radiator systems are an efficient and cost effective form of central heating. They are widely used throughout Europe. They work by circulating hot water through the panels of the Radiator and the warmth is released into the rooms by rising naturally from the metal exterior of the Radiator.

Radiators are a great option if you have a very small or no crawl space under your home. They have rapid heating and cooling times. They have flexibility with their controls in that if you have one part of your home that faces South and is usually cold the Radiators in this part of the home can be set to heat whilst the other Radiators in the North facing part of your home could be turned off and vice versa.

What Else?

Underfloor heating is not for impatient people. It generally takes much longer to heat up and cool down than other forms of central heating. This is partly due to the ‘thermal mass’ of the screed or concrete in which it is embedded combined with the lower operating temperature. If you are considering to retrofit your home keep in mind that it is critical to ensure your property is well insulated first. Many homes in New Zealand, especially older homes, are poorly insulated. You will need to check your insulation is up to current code before installing underfloor heating in order to reap the full benefits of it.

If your home is only occupied for a few hours in the morning and a few hours late at night, underfloor heating might not be the best option for you. Because underfloor heating does not heat instantly it might not be adequate to provide sufficient warmth.