Modern crawlspace waterproofing almost always involves complete encapsulation of the crawl space. This means that the crawl space is completely closed off from the surrounding environment. Nothing can come into the crawl space and nothing can leave the crawl space. This goes for air too.
However, is it good to leave the air in the crawl space as it is? One of the biggest arguments for venting crawl spaces is that moisture will build up in the crawl space and cause problems such as mold growth if it isn’t allowed to leave the crawl space.
First things first
Before looking at the argument for ventilating the crawl space, it is important to consider the different aspects of crawlspace waterproofing in order to better understand the air in the crawl space.
First, effective encapsulation of the crawl space involves covering all the walls in the crawl space. This means that air from the outdoors will not be able to move into the crawl space. This is good in a humid climate where the level of moisture in the air is high. You will want to keep out air to prevent the buildup of moisture in the crawl space.
If your contractor is any good, they will ensure that you have installed a vapor barrier in the floor of your crawl space. This ensures that moisture from the soil doesn’t penetrate the crawl space. Some vapor barriers also provide some degree of protection from toxic soil gases such as radon gas.
In many cases, the roof of the crawl space or the floor of your home isn’t covered. You may choose to install insulation in the subfloor to improve energy efficiency of your home. However, encapsulation of the crawl space will already significantly improve the overall energy efficiency of your home.
Where does the air go?
Moisture can still build up in the crawl space even after encapsulation. Sources of moisture include activities in the home such as cooking and bathing as well as utilities that run through the crawl space including HVAC and plumbing pipes. The air may therefore become humid.
If you want to avoid moisture problems in the crawl space, invest in a mechanical ventilation system. This draws moist and stale air out of the crawl space to ensure that moist air does not accumulate in the space. This in turn prevents mold growth and other moisture problems from occurring.
The answer to the question therefore is yes, you do need to ventilate your crawlspace for better results with crawlspace waterproofing.