Re: Crawl Space Under House
Kathy ...... is water from outside getting into the crawl space?
If so then you need to take care of proper drainage by ensuring the landscape slopes away from the foundation and down spouts drain as far away as possible.
If the water is extreme you might need to have some sort of drainage system that include a sump pit and pump to discharge any water entering the crawl space.
If the crawl space has a dirt floor and the moisture is from that then completely cover the floor with a minimum of 6 mil poly. This will prevent the moisture from migrating up from the dirt floor.
This is something you Don't want to do.
If it is just moisture from being damp I would insulate and cover the insulation with plastic, sort of a vapor barior, it will keep the insulation dry and avoid mold and mildew.
By covering the insulation with plastic on the underside of the insulation will trap moisture causing mold,mildew and rot.
You would better to cover the insulation with a house wrap material. This product will allow the moisture to breath out, minimizing any trapped moisture.
It's difficult to tell what your conditions are over the internet.
In some cases the vents can be contributing to the issue. Having passive vents open all the time can allow humid air inside the cooler crawl space and condense. If the winter temperatures are cold enough this humidity can freeze within until warmer temperatures thaw turning things into wet conditions.
One method .... depending as to the requirements in your area ..... is closing off the vents at least in the winter ..... and insulating the perimeter walls of the crawl space with rigid foam insulation. Doing this will raise the temperature within the crawlspace helping to keep the floor above warmer and minimizing condensation issues. If you live in an area with very cold winters also insulate the underside of the floor to assist with keeping things warmer.
If you have the budget then having 2 lb closed cell spray foam applied to the underside of the floor would be an excellent product and is immune to moisture issues.
If vents for the crawl space are needed or required you might consider having fans installed ina a push pul configuration controlled by a humidstat. Basically one fan would draw outside air in and the other fan would blow air from the crawlspace out. These would only turn on based on a set humidity level selected on the humidstat controller.
Hope this makes sense and helps
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