Are you asking if a vent fan is needed when encapsulating your crawl space? In this article we explain what we recommend per EPA guidelines when it comes to crawl space ventilation.

Foundation Vent Fan

The foundation vent fan is a concept pretty unique when it comes to building practices. Similar to attic ventilation, it is often overlooked and misunderstood. Many homeowners hear conflicting information from pest control and waterproofing companies about crawl space encapsulation vent fans.

Most foundation vent fans are constructed of plastic or metal. Many use computer style fans to move around 100 cubic feet per minute of air. Some place the fan to draw air into the crawl space. Some homeowners have the crawl space air being pushed out.

Whether your fan is pulling in outside air or pushing it out, the effect is pretty much the same in an open or vented crawl space. The make-up air is still being pulled from the air outside.

Vent Fan image

Open Crawl Space Vent Fan

Is having outside air enter your crawl space a bad thing? That depends on the humidity level of the make-up air. If you have an open crawl space in Knoxville, TN or Atlanta, GA chances are you are bringing in hot humid air.

Hot humid air hitting cold, poorly insulated and non-sealed duct-work is a recipe for mold and wood rot fungus. Mold and fungus can affect the sub-floor and cost you money in foundation repairs and floor stabilization.

Perhaps a vented crawl space in Denver, CO or Las Vegas, NV is not that much of an issue in regards to humidity. If the same principle applies with cold ducts in the crawl space, the hot non-humid air can still rob your home of air conditioning.

Using a Vent Fan with Encapsulation

This is where many get confused. For years, crawl space contractors have been sealing all the vents during encapsulation. In fact, many home builders create homes without foundation vents.

Why the drastic change? Research has shown an encapsulated crawl space has less mold, structural issues, and critters than an open crawl space. This doesn't mean all builders are closing crawl spaces but some won't build a vented crawl space.

The problem is soil gases. The crawl space companies and builders that close crawl spaces have created a problem while trying to fix others. When you seal all vents or build with no vents, the soil gases' only route is in your home.

Read our last article:

Crawl Space Encapsulation Dehumidifier

Vented crawl spaces certainly create more mold and structural problems. But, they allow nasty and potentially deadly soil gases to escape.

Installing a vent fan and performing crawl space encapsulation is the best scenario to address both problems. But there is another problem. Many contractors and builders do not include a dehumidifier.

That's like creating a well-insulated home with no heat source or air conditioner. No matter how good the crawl space is encapsulated, humidity, and other moisture problems still find a way to exist.

Crawl Space Encapsulation EPA Guidelines

I actually stumbled across the EPA (Environmental Protection Agency) guidelines by accident. I was researching open vented crawl spaces versus crawl space encapsulation and shocked at what I found.

I find it absolutely appalling that Crawl Space Ninja is one of if not the only company including ventilation and encapsulation.

The EPA says to install a foundation vent fan that will move 1 CFM of air for every 50 square feet of crawl space.

Did you know that? Did the last company that quoted your job tell you that? What about local codes enforcement, do they know what the CFM per square feet rating is?

This is why we look at your crawl space as a whole and try to make it worry-free. We are not just interested in the vapor barrier or a french drain. We don't remove mold without fixing its cause. Insulation and air sealing are not overlooked in crawl space encapsulation either.

When you hire Crawl Space Ninja, we explain how to fix the entire crawl space not just cover up or delay problems. This doesn't mean all homeowners follow or even like our advice. But that's not going to stop us from proposing the worry-free crawl space solution for your family.

I hope you found this information useful. Please comment below if you have any questions or would like to say hello. I am also putting a video for you to watch that could help further explain dehumidification and ventilation.

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About Michael Church

Michael Church has been involved with indoor air quality since 2005 and feels the unhealthy crawl space is one of the major problems causing poor indoor air quality.

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