The principle of solar heating is as follows: the solar thermal collectors placed on the roof or in the garden contain a coolant liquid (sometimes just water) which is distributed in the house once it is heated. Three types of facilities are available.

Firstly: water flows through a heated floor, which allows slow and continual heat diffusion. This facility is to be favored during a major renovation or construction because it requires redoing all the floors.

Secondly: a solar water heater, used to preheat water, is added to the existing central heating system. Moderately hot water is then transmitted to the boiler in order to complete water heating, this time at high temperature. The advantage of this type of facility is that it is not necessary to change the boiler or radiators.

Thirdly: if the existing central heating system has only one hot water tank of large volume, the water is heated mostly by solar collectors, assisted by electrical resistance.

Solar energy can only satisfy 30 to 60% of the house’s heating requirements. It is therefore necessary to associate a backup system.
Another interesting fact is that the installation of solar panels on the roof of your house or in your garden gives you a tax credit of 50%. However, the government plans to reduce the credit to 10% in 2011.