What types of underfloor heating are there in NZ?
Updated: 4 days ago
There are three main types of underfloor heating used in New Zealand: electric cable or mat laid under the final floor covering, electric cable or water pipe cast into a concrete slab, and hydronic systems that circulate heated water. Heatwell installs and services only the electrical cable style. Each suits a different kind of project, and the difference that matters most is whether the floor is already built.
Electric cable or mat under the floor covering.
The most common method in New Zealand, and the only one that works as a retrofit.
The heating cable is fixed to the prepared subfloor, fibreglass mesh is laid over it, and self-levelling compound or screed is poured on top, encasing and protecting the element. It adds about 4mm to the floor height — budget 5mm. The floor covering goes over that.
It suits small and medium areas, which is why bathrooms and ensuites are where most of it goes, and it is the method of choice for renovations because it goes on top of what is already there rather than inside it. It is controllable room by room, it responds within an hour or two, and if a thermostat fails it is a wall-mounted part that gets swapped.
Electric or water cable cast into concrete.
Heating installed inside the concrete slab when the slab is poured. This is a new-build decision and it is usually chosen when the whole floor is being heated. It uses the thermal mass of the slab, so it is slow to warm and slow to cool, which suits continuous heating and does not suit heating a room for a couple of hours in the morning and evening.
In slab floor heating needs to be careful planning. Once the concrete is poured nothing can be changed, and a fault is difficult and expensive to find and fix. Heatwell does not install or service in-concrete systems.
Hydronic, or water-based underfloor heating.
Pipes circulating heated water, traditionally from a gas boiler, sometimes from a heat pump.
It was more popular in New Zealand than it is now. Two things changed: it adds at least 10mm to the floor build-up, which is a lot in a renovation, and gas prices have risen substantially, which has taken away much of its running-cost advantage. It also brings a boiler, a manifold, pumps and valves — more equipment to maintain than an electric system has.
It still makes sense for whole-house heating in a large new build, particularly one running it from a heat pump. Heatwell does not install or service hydronic systems.
What about foil mats and thermopads?
These are a variant of electric heating sold as a thin foil mat laid loose under the floor covering rather than screeded in, and Heatwell does not recommend them.
The reason is crushing. A foil mat or thermopad should not be installed in a high-traffic area or under heavy furniture, because the heating cable in them is likely to be crushed. A crushed foil mat or thermopad creates a fire risk very similar to the way a damaged electric blanket does.
The mesh and screed method avoids this entirely. Once the cable is locked into a reinforced concrete structure, heavy furniture and high traffic will not damage it — which is why Heatwell is comfortable recommending underfloor heating under a bed, and foil mat suppliers are not.
Which type should I choose?
| Electric under the covering | Cast into concrete | Hydronic |
Retrofit possible | Yes | No | Rarely |
Added floor height | About 4-5mm | None | 10mm or more |
Response time | Fast | Slow | Slow |
Repairable | Yes | Difficult | Moderate |
Best for | Bathrooms, bedrooms, renovations, room by room | Whole floor in a new slab | Whole house in a large new build |
Heatwell installs | Yes | No | No |
Can I mix types in one house?
Yes, and it is common — a slab system in a new living area, electric under the bathroom floor.
Which is cheapest to run?
It depends far more on insulation, floor construction and how the system is scheduled than on which type it is. An insulated floor on a sensible schedule beats an uninsulated one of any type.
Does Heatwell service other companies' systems?
Heatwell installs and services electric cable under the floor covering, and does not work on in-concrete or hydronic systems.
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