Crawlspace ventilation

It is very rare I enter a crawlspace under a home and don’t find some sort of concerns. Let’s face it, it’s nasty underneath most homes. Therefor, homeowners typically don’t go under often and this allows small problems to turn into potentially larger issues.

In our local area we have a large coverage area of good draining sand (close to the beach) and poor draining dirt.

We have entered into a rainy season and the grounds are soaked, thus creating even more problems. More research is being done in closing in crawlspaces and making them essentially “conditioned” spaces, similar to our homes. I really like the idea and have seen only a few homes that are employing this method. These few that I have seen were relatively dry and had few problems.

Some building codes are starting to adopt these changes and I, for one am looking forward to seeing more upgrades to these areas. I recently attended a spray foam school where they showed their approach to keeping a crawlspace dry. It looks like it will work well, time will tell for sure.

I did a home inspection recently and the buyers wanted a thermal image of the crawlspace, so here it is…Remember warmer temperatures are brighter in color. This crawlspace had a very good vapor barrier with open air vents.

Below is one of the building guidelines for closing in a crawlspace. Remember every home and situation is different, do lots of research before making any changes to your home.

Traditional crawlspace designs include passive foundations # wall vents that are supposed to let moisture and contaminants escape outside. Yet field research shows that wall vents may make moisture problems worse. Replacing crawlspace vents with an exhaust fan and drawing house air in to condition the crawlspace reduces moisture problems and can increase energy efficiency. The International Residential Code (IRC) specifically allows crawlspace designs with an exhaust ventilation system instead of fixed ventilation openings through the foundation walls. To comply, a mechanically vented crawlspace design must have a continuously sealed, vapor-retarding ground cover, have no fixed ventilation openings to the outdoors, and be supplied with a continuously operating exhaust fan.