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Top 4 Worst Crawl Space Insulation Practices You Need To Know

Most homeowners interested in insulating their crawl spaces end up searching for that information on the internet. Yes, there are lots of good information online, but there also very bad and outdated advice being given out there. The most common worst practice is using fiberglass to insulate a damp crawl space. This is because fiberglass absorbs and holds moisture from the foundation walls and ground, and when its too heavy it falls. This leads to rot, excessive moisture and mold growth. Here are more worst crawl space insulation practices that youve probably not heard of before.

Adding More Foundation Vents To Your Crawl Space

Due to bad advice and old building codes, homeowners are adding more vents to the crawl spaces with the intention of drying excessive moisture. The thinking behind this practice was that circulation of air (ventilation) would force moisture in the crawl to go outside. However, it has been proven that adding warm and humid outdoor air through the foundation vents leads to increased levels of moisture in the crawl space. Proper encapsulation is the only effective way to reduce high levels of moisture in the crawl space.

Spray Foam On A Damp Crawl Space Foundation

In dry, below-grade crawl spaces, using spray foam insulation is the best for maximum energy efficiency. However, theres only one problem. Many below-grade crawl spaces have ground floors and foundations that are not dry. Hence, choosing this form of insulation for a damp crawl space can lead to moisture being trapped in the wood, causing rot and weakening the structure of your home. So, unless your crawl has a foundation waterproofing membrane, footing drains, foundation sealant and downspout extensions, youre better off not choosing this form of insulation.

Insulating Heat Ducts With Fiberglass

If insulated with fiberglass, ducts in vented crawl spaces are likely to condense, and the fiberglass will absorb this excess water, leading to mold growth around the fiberglass ducts.

Improper Installation Of Drainage Systems

After heavy rains, most crawls usually have standing water on their floor grounds. And as you may already know, you cannot insulate your crawl space effectively without first tackling water and moisture problems. Most homeowners try to solve this problem with a sump pump and a stand -alone pit. But, a sump pump alone is not enough to pump all the water, which collects around the crawls perimeter or center. To intercept the standing water and lead it to the pump, a perimeter drain is necessary.

To protect your home, avoid these unprofessional crawl space insulation practices at all costs if you can. For more information about crawl space insulation head over to


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