- 8 May 2020
- Posted by: Eddy Cruysberghs
- Category: Building physics
Every house makes a bell-jar. Place a transparent bell-jar on the ground and very quickly condensation moisture will appear on the inside. This is because of the vaporisation of the moisture in wet sand and the increasment of the underlying vapour pressure. In addition, the possibly present Radon gas (radioactive harmful gas) will escape from the soil and gather in this bell-jar.
Make some holes in the bell-jar and the condensation will disappear. The high underlying vapour pressure, the moisture and the harmful Radon gas can directly escape.
The picture below clarifies this. In the left bell-jar the moisture and the harmful Radon gas collects at the top. In a house of apartment this is exactly the same. An automatic cumulation on the upper apartment occurs. This is never occupant behaviour.
The floor construction above this bell-jar is not 100% vapour tight (µd > 100), because of which the floor inevitably will absorb the moisture from under the bell-jar. The absorption of this moisture costs 30% on the heating costs.
In the best cases the floor is constructed out of concrete, a pressure layer, insulation material, a screed and a finishing layer with a total vapour diffusion reducing resistance of about µd 15 – 18%. This means that 82 -85% of the underlying moisture is absorbed by the warmer air from the living room.
So how will you get every house, building or apartment energy neutral by tomorrow?
Pay a little attention.