Underfloor heating contributes to sustainable living

Energy efficient invisible and comfortable!

In new construction projects and renovation of existing housing there is a strong focus nowadays on comfort and low energy consumption. As a result, underfloor heating in becouming increasingly popular. Ideally suited in combination with Low Temperature Heating, underfloor heating provides a comfortable indoor climate and is also energy efficient.

A good example is the Underfloor Heating Lake District project from Cumbrian Homes:

(image by Interior Photographer Glasgow)

Invisible

The main advantages of underfloor heating are the even heating of the living space and, thanks to the radiant heat, a high comfort level at a much lower air temperature (19 to 20 degrees) than with conventional heating. Thanks to this lower temperature there is less heat loss, the return is higher and sometimes there are substantial energy savings. Also aesthetically underfloor heating is an asset, because it is invisible. The sometimes very ugly radiators can be ditched. Furthermore, underfloor heating generates less air and therefore less dust displacement. This makes this way of heating healthier and more hygienic than alternative systems. And as last advantage we can mention that with a underfloor heating system there is also the (optional) possibility to cool the House down in the summer. This is achieved by using chilled water from for example, a chiller, a heat pump, or with water from the deeper surface (aquifiërs).

Hot water and electricity

There are basically two ways of underfloor heating: by means of hot water and electric systems. With a hot-water underfloor heating system, the heating pipe (with a diameter of 16-20 mm) runs through a special control unit, the Manifold. The Manifold is connected to the existing boiler or other other heating source such as geothermal energy combined with a heat pump. An alternative to the system with an underfloor heating manifold is through a tube connecting it to the return water of a radiator. This is widely applied in areas where both are present such as bathrooms. For new buildings the pipes are usually embedded in the concrete subfloor in the form of a spiral or meander. The advantage of the spiral form is that supply and return are always next to each other, resulting in a more even heat emission. For existing construction screed can be applied on top of the existing floor or boards are used. Here are the pipes directly in the surface and this will warm the floor faster. Downside is that the floor will also cool down quicker. An electric floor heating consists of thin mats on/in which the heating elements are mounted. Advantage of an electric underfloor heating is that this is easy, fast and relatively inexpensive to install. On the other hand, the power consumption is higher.

The manifold

The manifold is, as it were, the traffic regulator and has the function to distribite the hot water from the central heating boiler or other heat source into the heating pipes. The water circulates in the pipe system to this extent that the thermostat has cooled down, add hot water is released again. There are multiple types of manifolds in circulation, but the most important is the open manifold with circulation pump and preset mixer. On the maniufold multiple groups (2-12) can be mounted and it has a mixing scheme with which the connection to the central heating system is managed. The different heating groups can be individually adjusted and also switched on and off. In this way, the temperature in each room can be set separately very accurately.

Low temperature heating

Underfloor heating is excellent for interfacing with low temperature heating. This is possible with the normal central heating boiler, but it is better in  combination with geothermal heat and a heat pump. With low temperature heating with a boiler the supply and the return temperature of the boiler water is significantly lower than the usual values of conventional heating systems with radiators. The flow temperature will not exceed 55 degrees and the return temperature is somewhere in the region of 45 gaden. When geothermal heat in combination with a heat pump is used, the supply temperature can be as low as 30 degrees. Also cooling is possible with underfloor ‘heating’ systems. Obviously that requires a custom installation and usually involve closed manifolds who do not mix and special thermostats are required as well. The water is usually indirectly cooled through ground water from the primary circuit of the heat pump. We call this a free cooling. It goes without saying that the energy consumption with this method of cooling is significantly lower than with air conditioning. A major point of concern is of course that you don’t allow the floor to get too cold, otherwise condensation can occur.

Electric underfloor heating

An alternative for low temperature underfloor heating is electric underfloor heating. We distinguish three different forms: embedded cables in the floor, thin heatingmats of textile or fiber with a curled pattern of thin (2-3 mm) insulated resistance wire, covered with conductive foil carpet or laminate. 

Electric underfloor heating is fitted directly under a tiled floor or under another thin finish and the floor hardly increases in thickness. In most cases, people are advised to use electric underfloor heating only in small spaces as additional heating, although it can also serve as the main heating system. That, however, requires a capacity of at least 190W/m2 when about half of the floor area consists of electric underfloor heating. 

Finally, it is worth mentioning the principle of infrared underfloor heating. This heating technology is based on amorphous metal, a metal alloy that submits infrared radiation. The heating elements of the underfloor heating system consist of Ribbon elements, metal strips of just 25 microns thick that produce heat through infrared radiation. These ultra thin metal strips are processed in mats or panels.