Foil for floor heating. Need or not?

    Everyone who has encountered the theme of heating floor knows that it needs to be "warmed up". As a thermal insulation often, use expanded polystyrene with foil. However, here is the question, why is it needed? In addition, is it necessary at all?

Picture 1. Example of laying the floor heating loops

Immediately I want to dispel one myth that the foil reflects heat. And it is distributed only in the right heated room. It is not true!

I will explain. In heating, there are three main types of heat transfer - convection, heat conductivity and radiation. The latter method can only work in a transparent environment. Since there is no interlayer between the foil and the concrete, it cannot reflect (radiate) the heat.

However, to give away heat due to heat conduction - yes. Since the coefficient of thermal conductivity of concrete is much lower than that of aluminum foil, the latter contributes to rapid warm-up and uniform heat distribution over the area of ​​the room. To achieve this effect, it is necessary to use aluminum foil with a thickness of more than 50 microns. 

Nevertheless, with a greater share of probability, this film will not be able to serve you for a long time, since the concrete can "eat" aluminum. This is due to the alkaline structure of the cement-sand screed.

Picture 2. Consequences of contact of aluminum foil with screed

And all the effectiveness of having a foil - disappears.

Because it is better to use specialized mats under the warm floor. They have a polymer coating, a convenient system for fixing pipes, are durable and reliable.

Picture 3. Special panels for the "Warm Floor" system