Crawlspace Construction

[Stattick]

I just purchased a new home in Regina, Saskatchewan, Canada. Built in 1965, original portion of the house has a full basement, the addition on the house (1982) has a crawlspace(unheated). The crawlspace is approx 24". The construction from ground up is natural ground, poly, 6" sand, poly, crawlspace air with concrete perimter walls, 2x10 joist insulated, poly, subfloor.
The crawlspace is humid. the poly layer on top of the sand is badly done. it is laying loose on top of the sand. the sand is very wet under the poly but where the sand is exposed it is dry.

Anyone that knows the weather we deal with knows that the furnace runs strong in the winter and the AC runs strong in the summer.

Is this construction correct? I have a daughter with a lot of allergies and I want to make this right before we move in in about 5-6 weeks.

Thanks in advance for help and advice.

[Wgoodrich]

You have a problem with double vapor barriers. I would leave the vapor barrier under the sand to block out moisture from the earth. Then remove the poly [aka vapor barrier] from on top of the sand, then check the floor insulation. If with a paper back insulation most likely remove that insulation also because that paper on the insulation is also a vapor barrier. Then the poly at the floor level remove that vapor barrier also. The moisture is being trapped. Only one vapor barrier should be installed in an area or you are trapping moisture between the vapor barrier.

Then I would install one crawl space vent for each 150 square feet of crawl space installing at least one of those vents within 3' of each corner of your crawl. I would install the temp sensitive vents that close when the temperature outside gets cold or save the pieces of the styrofoam insulation you cut out for the vents to install each fall and remove each spring.

Then in your area I would install 4" of styrofoam insulation around the perimeter of the crawl space leaving the floor joists open.

This should create warm floors, lack of frozen pipes, greatly reduced moisture in your living area.

YOu basement if utility use I would install a minimum of 3" styrofoam directly against the masonry or 4 1/2" of fiberglass insulation maintaining a 1" air gap between the masonry wall and the fiberglass.

Hope this helps

Wg

[Bumblerazz]

The only thing I would add is have a minimum of two vents to allow for a cross breeze (I am taking your word that the crawl space is 24 inches and not 24 feet). The sand will dry out and stay dry and in winter block the vents with the foam that Wg mentioned.