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Sealed Crawl Spaces and New Construction

By: Jasna Aleksandrova

The last of our series of crawlspace blogs for the year…

Opinions are divided when talking about vented or sealed crawlspaces. Some of the older building regulations state that crawlspaces need to be vented, but new research shows that the opposite is true, sealed crawlspaces are much more energy efficient than vented ones. That’s why newer building codes allow crawlspaces to be sealed. The questions: Is this necessary? Why not stick with the old building codes? However, everything is done for a reason and over the years new concepts have shown that sealed may be better. It is important for you to know the advantages of sealed crawlspaces over vented ones.

Benefits of sealed crawlspaces

As stated above, many people have come to the conclusion that a sealed crawlspace is more energy efficient than a vented one, however, when you have a sealed crawlspace there are other factors that you should keep in mind which I will talk about below. When you seal your crawlspace, you can prevent moisture from building up thus protecting the wooden structure of your house, on the contrary, traditional thinking is that protection is best done by venting your crawlspace. By venting your crawlspace, moisture will not magically escape but the vents will allow the outside air to come in which can spell trouble. In the summer, when it’s hot and humid, vents allow that air in. When hot air meets the cool surfaces inside your crawlspace, the air condenses and creates moist conditions that are perfect for wood decaying molds and the moisture will also attract insects. The same problem exists in the winter when the cold air from outside meets the warm air inside your crawlspace. Although running air conditioning and heating into your crawlspace can increase your electric bill, it can help maintain temperatures inside your house during the summer and winter making your home more temperatures more comfortable while it keeps your crawlspace dry.

Proper encapsulation of the crawlspace

It’s important to let you know that a well sealed crawlspace can prevent moisture from building up; however here’s something you may not have thought of… there are natural gases in the soil under your house like radon and methane, which you don’t want to enter into your living space above. The crawlspace floor should be layered with a 6 millimeters thick (minimum) polyethylene plastic and the plastic should be taped at the seams and sealed onto the walls of your crawlspace. Perforated plastic pipes should be installed underneath the plastic and directed outside to prevent gases from getting in to your house. Thick insulation must also be placed on the walls of the crawlspace. If you aren’t sure which thickens to choose, the best thing is to use the same thickness that has been used for the upper walls of the house. By doing this, your crawlspace will be better protected from soil gases and will maintain a more steady temperature throughout the year.

Crawlspaces in new home construction

Crawlspaces in new construction make sense for most because all of the fittings, water pipes, drainage pipes and even electrical wiring are stored there making them easier to get to and easier to maintain. Also crawlspaces can prevent pipes from freezing when proper temperature levels are maintained and some people even find their crawlspace to be useful for storage. Remember, when building a new crawlspace as your foundation, it is imperative that it must be left open to dry out and it should then be properly protected as stated above. If not then moisture may appear more quickly after the home construction is finished.

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