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Imagine you are sitting in front of a fire. The high temperature of the fire emits waves directly to you, without heating the air. Those waves will keep you warm. And those waves are called radiant heat. However, the majority of heat of a fire is actually given out via heating air. As air brushes past the fire, it heats up and rises, allowing more air to heat. Radiant heaters heat up bodies, that reflect heat back into the surrounding air. This is a more comfortable and natural way to heat (same as the sun), that is comfortable at a slightly lower air temperature than air heaters (between 1-2 degrees Celsius).

 

According to the master plumbing organisation in NZ, underfloor radiant heating devices that we will cover soon, warm bodies with radiant heat to about 60% and heat the air with about 40% of the energy (1). All radiant heaters tend to be more efficient than air heaters because of the way the heat is distributed.

 

Underfloor heating

Underfloor heating is one of the types of available radiant heat. Underfloor heating is considered to be one of the most comfortable ways to heat your home or building. Reason for this comfort is threefold:

• Underfloor heating works on a low temperature coming through the floor, creating thereby only minimal airflow

• Underfloor heating creates very few hot of cold spots in homes, as the heat is evenly distributed

• Underfloor heating has the warmest air temperature on the floor. As the warm air rises off the floor, it mixes with its surrounding air and cools slightly down, creating comfort

 

In New Zealand, there are different versions used in underfloor heating.

Many people choose to install the pipes for heating in the actual concrete slab. Fitting in the slab has the advantage of adding thermal mass, a storage battery for when you need it. This means that if you have a warm floor and for a couple of days no fuel to power your heating, you stay warm most of the time.

 

The disadvantage of installing in the slab is the speed of heat. It will take a few days for the floor slab to be heated up properly to heat your home. Another advantage or disadvantage is that it is difficult to regulate the heat: even if you turn off a valve in one room, some of the heat from the neighboring pipes will go to colder places in the concrete slab and thereby lost. Also, it is vitally important that if you do use a floor slab underfloor heating system, to use a fully insulated floor slab. In NZ, there is as of the beginning of 2020 no regulation for the sides to be insulated.

 

Another version is to install them on top of the concrete slab and pouring a so-called screed on top of the pipes. The screed acts as a smaller thermal mass, storing less heat that the floor slab. The advantage of this method is that here you can heat different rooms as you please without heat loss. The time it takes to heat a room is also faster. However, as said, you will not be able to store as much heat as by installing the pipes into the slab.

 

A third option is electric underfloor heating. Here, wires are installed underneath tiles. Whenever you turn on the heating system, the wires heat the tiles to give you warm feet. Electric underfloor heating is usually used in bathrooms. The advantage of those is that the heat is going through very fast and with minimal heat loss. The disadvantage is that it is expensive to create heat purely with electricity. Using a heat pump, gas, diesel or wood are cheaper forms of heating in most areas.

 

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