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Crawl Space Insulation Best Practices: An In-depth Look At Moisture Control

The ill-effects of poor crawl space insulation include significant energy losses, uncomfortable indoor temperature during summer and winter, excessive moisture accumulation, pests and mold growth. That said, its important to understand that effectively insulation the crawl space goes beyond just installing the right type of insulation material. Other key practices include providing sufficient drainage, choosing the right method of installation, sealing all air leaks and controlling moisture. Lets take a look at moisture control in particular.

Control Of Moisture Accumulation

Moisture accumulation is one of the visible signs of a poorly insulated crawl space. There are two main sources of moisture: the ground, and the outside air. Until youre able to eliminate these sources, you cannot effectively insulate your crawl. Lets look at each of these sources in detail. By the way: if you would like to read even more interesting information about crawl spaces and how you can isolate them, then we advise to take a look at http://www.regioisolatie.nl/waarom-kruipruimte-isolatie/.

a) Control Ground Moisture Using a Vapor Barrier

Ground water is likely to evaporate into your dirty-floored crawl and soak the wooden structures and joists. Additionally, it will also filtrate your floor and concrete walls, making them damp most of the time. Though most contractors and even building codes recommend that you line the crawl with waterproof ground cover to prevent water evaporation into this space, this wont address the problem of water sipping through the walls.

Therefore, to effectively control ground moisture from the crawl space, consider lining the area with something that will completely isolate it from wall and ground moisture. What am I talking about? Line the entire space (walls and floor) using a flexible poly sheet vapor barrier if you leave in an area with a warm climate. If you properly air seal and condition the crawl, you wont need to add insulation. However, if you live in an area with a colder climate, consider using both a vapor barrier together and a foam board to provide thermal protection as well as a vapor barrier.

Many people tend to use 6mil poly sheet to line their crawl spaces, but for better and lasting results, its recommended that you use 10 or 20mil poly sheet liner instead. Be sure to fasten the liner to the walls so that it doesnt tear easily when crawled on during maintenance visits and inspections.

b) Air Seal The Crawl Space To Control Outside Air And Moisture Infiltration

During warmer days, the outside air will cool down, when allowed to enter the crawl via the vents. When this happens, the RH (Relative Humidity) will increase by about 2 percent for every degree that the outside air is cooled. When the RH levels rise above 60 percent, mold will develop, and this occurs quite often during summer.

RH levels arent so much of a concern during winter, but if youve got pipes and ducts in your crawl, some condensation might occur. The biggest problem for most homeowners during winter is the infiltration of cold air into their living space. As you may have already noticed, the floor and overall indoor temperature usually becomes colder during colder months.

This is where air sealing comes in. The main goal of air sealing is to enhance your homes energy efficiency. Without it, crawl space insulation wont be as effective. So, make sure your access to this space is through an outside entry, which you can effectively air seal when not in use.

Overall, moisture control is an important component of effective crawl space insulation that you should never ignore. When done properly, it can eliminate mold problems and rot, thereby protecting your familys health and your homes structural integrity.

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