How can the humidity level be controlled under an entrance room? The entrance to our triple brick farmhouse is a 12 x 11 foot, studwall construction, room built on a rough concrete foundation wall, which in places must be at least 8 feet deep. Under the floor is a large old water cistern, approx 6 feet deep (no longer used) and one end of the holding tank for the septic system. The cover for the septic tank is a 2 inch concrete slab fitted on a concrete lip with a thick rubber seal. The under floor space is very damp. The original floor and beams (probably over 60 years old) were completely rotted and have been replaced with modern PT lumber. The humidity is sufficient that water beads off the metal joist ties, bolts, and inside of the foundation wall in some places. The floor is not yet insulated and the room is not directly heated.
Any suggestions please?
There is a couple things you can do. Since it's not a heated space then put in 2 vents in the walls of the crawl space so that you get a cross flow from the outside when the wind is blowing. The next is to remove or at least fill in the unused cistern, you don't want any water to collect there. The last is to put down a good quality vapour barrier and cover the entire floor of the crawl space. Make sure it's sealed to the walls and around the cover of the septic tank as well as possible. This will keep the moisture in the ground from entering the space.
If you do end up heating the entrance way then insulate under the floor with as much spray foam insulation as you can get in there. All the other recommendations should still stay in place.
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