Are there risks with negative pressure ventilation of slab on uninsulated ground
We have a 1970s house with an uninsulated slab on a gravel bed (not gravel or washed gravel). Spike battens were cast into the slab. We've had some problems with ground moisture, but now we had a water leak due to a screw that was once driven through a cold water pipe. The water leak has been found. Floors, battens, and spike battens (which were embedded in the slab) have been removed, and now everything is drying out with a dehumidifier.
Now that everything has been removed, we're considering installing Nivell's subfloor ventilation system with Nivell's batten system during the reconstruction.
- Are there any risks with installing subfloor ventilation? I understand that it's very important to seal against exterior walls, interior walls that are not part of the ventilation, against penetrations of water and electrical lines, and against holes and cracks in the slab. This is to prevent drawing in new moist air and to avoid disrupting the airflow across the slab.
- Is there a risk that warm indoor air, which can have quite a high vapor content (g water/cubic meter of air), is cooled when it is drawn down under the floor to the slab and condenses there?
- Is there a risk of a crack in the slab that isn't visible, where you draw in moist air from the underlying gravel bed?
- What could happen in the worst case if all seals are not airtight?
- What are your experiences with installations of subfloor ventilated floors?
Now that everything has been removed, we're considering installing Nivell's subfloor ventilation system with Nivell's batten system during the reconstruction.
- Are there any risks with installing subfloor ventilation? I understand that it's very important to seal against exterior walls, interior walls that are not part of the ventilation, against penetrations of water and electrical lines, and against holes and cracks in the slab. This is to prevent drawing in new moist air and to avoid disrupting the airflow across the slab.
- Is there a risk that warm indoor air, which can have quite a high vapor content (g water/cubic meter of air), is cooled when it is drawn down under the floor to the slab and condenses there?
- Is there a risk of a crack in the slab that isn't visible, where you draw in moist air from the underlying gravel bed?
- What could happen in the worst case if all seals are not airtight?
- What are your experiences with installations of subfloor ventilated floors?
Nivell floors are recommended for uninsulated slabs. It's certainly a bit of a task to get sealing and airflow right in an old house. Any smell from the slab should not be led up if the construction is correct. Interior walls can be a problem if there is embedded material under them. The walls remain unventilated unless the floor is laid underneath (difficult to chisel under walls). It might be worth considering the overall situation if you later plan to install ventilated flooring in other rooms as well, in terms of where the air should be ventilated and the placement of the fan.
Check the websites for the systems and call and talk a bit with them. Besides Nivell, there are Jape, Granab, and Platon that offer similar solutions.
Check the websites for the systems and call and talk a bit with them. Besides Nivell, there are Jape, Granab, and Platon that offer similar solutions.