Instead of having a forced air heating system we used what is known as hydronic radiant floor heating. In this system, hot water is circulated through polyethylene pipes installed in our concrete slab floor. Heat is conducted to the surface of the floor where it broadcasts energy up into the room. Radiant floor heating is superior to convection heating because warm air will rise wastefully to the top of a room, especially in a large, two-story open space like our dining room. This is not only inefficient, but also tends to heat the head and the upper parts of the body, while leaving the lower parts of the body cold, which can lead to discomfort. Radiant floor heating warms the lower part of the room and the body, making more efficient use of the thermal energy and creating a more “natural” feeling of warmth. Underfloor heating is also more efficient than a traditional radiator system, because the large surface area of the heating element (i.e. the entire floor) means that the boiler water temperature can be set relatively low.

We had hoped to use the solar thermal collectors to heat the water that flows through the floor heating system, but we were unable to do so for permitting reasons. We were told that we would not be allowed to link the two systems because the solar thermal collectors are used to heat the potable water in the building, and the water running through the floors is not potable. So instead, the water is heated using a 97% efficient condensing boiler, which uses half the amount of energy as a traditional water heater to heat the same amount of water.