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Vented Crawl Space Insulation: Your Ultimate Step-by-step Guide

A crawl space refers to the unfinished, accessible area beneath a buildings first floor. The number one purpose of crawl space insulation is to enclose it in a thermal envelope so as to prevent energy loss. A crawl space that is properly sealed, protected from excessive moisture and insulated can significantly reduce your energy bills, improve your comfort and the durability of your home, and decrease entry of radon and other potential irritants into your home.

How you go about the insulation process depends largely on whether you have a vented or unvented crawl space. In vented crawl spaces, only the under-floor should be insulated. However, if your crawl space is unvented, you need to insulate the perimeter walls. Heres a step-by-step guide on how to insulate your vented crawl space.

How To Insulate Your Vented Crawl Space

As a general rule, only the under-floor should be insulated in vented crawl spaces. Heres a guideline to follow for effective insulation:

1) Seal air leaks between the crawl and your homes conditioned space. High priority should be given to the holes around your bathtub drains and plumbing and electrical wiring penetrations.

2) If you have framed floors, youll need batts with attached vapor barrier for insulation. Cut the batts to the joists full length and slit them to fit around plumbing and wiring. Since complete coverage is very important, ensure that you do not leave any insulation voids.

3) Install the batts tightly against the subfloor in order to eliminate gaps, which may allow cold air to flow between the insulation and the sub-floor. Insulate the area between the floor and the air ducts, water lines and all ductwork in the crawl. Make sure you use mechanical fasteners to fasten the insulation in place and prevent it from falling out in the coming years.

4) Cover your insulation using a vapor barrier or a house wrap.

5) Carefully install the polyethylene vapor retarder on top of the dirty floor, ensuring that you secure and seal all seams. To protect the polyethylene from damage, consider covering it with concrete or a very thin layer of sand. However, be careful not to use anything that can create holes like crushed gravel.

6) The orientation of your vapor barrier will largely depend on your homes climate and location.

7) Close all the vents within the crawl after making sure that the crawl is completely dry, and all construction materials have dried out.

Overall, an effective crawl space insulation strategy goes beyond just installing the right insulation material. You also have to put in place measures to reduce moisture levels, seal every air leak between the outside and the conditioned space, and mitigate radon and other pollutants from entering your home. Implement the above steps and transform your damp, dirty and energy-wasting crawl into a clean, dry and durable space that will reduce your homes energy consumption and improve your interior comfort.

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