Underfloor heating: is it worth it in Cape Town?

As autumn arrives and the first cold mornings come, underfloor heating is a common request, especially for bathrooms and open-plan living areas with tiled floors. Cape Town winters are mild by international standards, but our houses are often poorly insulated, and tiled floors are cold. Here is what you should know before deciding.

How it works

Underfloor heating warms the floor, which then gently warms the room. Because the heat comes from the whole floor, it feels even and comfortable, with no hot and cold spots and no radiators or heaters taking up space.

Electric systems

Electric systems use heating cables or mats laid under the floor finish.

Installation: relatively simple and cheaper to install, ideal for bathrooms and smaller areas.
Running costs: heat comes from electricity, so running costs can be high in large areas used for long hours.
Best for: bathrooms, en-suites and single rooms.

Water-based (hydronic) systems

Water-based systems circulate warm water through pipes embedded in the floor screed. The water is usually heated by a heat pump or a boiler.

Installation: more complex and more expensive to install, and needs a deeper floor build-up. Usually only practical in new builds or major renovations where the floors are being redone.
Running costs: lower, especially with a heat pump, which uses much less electricity than direct electric heating.
Best for: whole houses and large open-plan spaces.

Which floors work?

Tiles and stone: the best, because they conduct and store heat well.
Polished concrete and screed: excellent, as the heat is stored in the slab (see our post on screed and polished concrete).
Engineered timber: works with suitable products and controlled temperatures. Check with the flooring supplier.
Carpet and thick rugs: reduce efficiency.
Solid wood: generally not recommended, because of movement.

Insulation is essential

Without insulation under the heating, much of the heat goes into the ground or the slab below. Insulation boards under the heating element make a big difference to running costs and warm-up times. In an existing house, roof insulation should come first: a warm floor in a house that loses heat through the ceiling is a waste of money.

Controls

Use a thermostat per zone, with timers. Underfloor heating works best when set to come on before you need it, since it takes time to warm up, especially water-based systems.

Power and backup

Electric underfloor heating draws a lot of power and is usually kept off backup inverter circuits. Plan this with your electrician, especially if you have solar (see planning solar into a renovation).

Is it worth it?

In a bathroom, electric underfloor heating is an affordable comfort that most people love. For a whole house, a water-based system with a heat pump can be worth it in a new build or a major renovation, especially in larger homes. As a retrofit under existing floors, it rarely makes sense.

If you are planning new floors or a bathroom, ask us about including underfloor heating.