How to avoid condensation under the floor?

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Condensation has formed under the floor. The structure is as follows: Strip foundation 60 centimeters above the floor (underneath sand), Beams (150x100) on the foundation, the beams laid insulator Paroc, under the beams punched a bar 50x50, which is also laid insulator to the total thickness of insulation to 20 cm, then Ondutis SA 115 wind moisture barrier and lath-inch to lie on top of the insulation.

As a result, the water is located in large drops on the entire windbreak. The insulation is dry at the same time (the wind barrier keeps water out).

The air holes are made in the foundation (110mm, 4 pieces for each part of the house 8 to 4 meters), and near the air holes foil is dry, but literally in a radius of 1 meter.

Now I force a fan near one of the vents to let fresh air into the house. But that's not the solution. How do you deal with condensation?



Moisture appears from temperature differences.

If the temperature of the basement and the living space are not much different, there will be no condensation. The source of moisture in the basement may be upward flows from the ground beneath the house or moist air driven from the street by your ventilation system. Or both. In order to calculate the cause.

1. Seal your vents. Make the air communication between the basement and the room above-align the temperature (sometimes simply opening the lid (hatch) or organize the air vents through the adjacency of the floor to the wall. You can equalize the temperature by heating the air in the basement with an electric heater.

2. If after the alignment of temperatures the moisture remains-the source of upward flow from the ground. Cut them off by waterproofing the soil (floor cellar) and waterproofing of the foundation.

A common mistake is to first let the moisture into the basement and then heroically air it out through the holes in the basement, while launching new portions of moisture.


If the sand under the house is dry, the condensate – this from the temperature difference, as a bottle of water from the fridge in the heat.

Option of occurrence: the house is heated, it is warm inside and under it, under the floor, is also warm (may be little insulation), and the cold air penetrates into the air vents at night.


Your vents are obviously too small.

If the floor insulation is already done, then only increasing the size of the holes will be the cheapest option. And probably put a film on the ground.


Start by buying a weather station with a remote sensor. Place the sensor in the basement, in the dampest place. Start observing.

Try to change the position of the fans in the vents, the heat fan inside the basement, by lifting the pipes through the corner of the vents along the wall on one side. On the basis of the indicators you will be able to draw conclusions

There may be differences in winter and summer. The humidity of the basement is a purely individual value and many components can affect it.

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