Breathing nasty crawl space air makes people sick. Overlapped separate sheets must be lapped at least 6 inches.
Crawlspaces that are constructed to be unvented air-sealed insulated and conditioned can have several advantages over vented crawlspaces see Figure 1.
Crawl space sealed or vented. This closed crawl space intervention consisted of sealed foundation wall vents a sealed polyethylene film liner and 05 Ls 10 ft 3 min of air supplied by the heating ventilation and air conditioning HVAC system for each 28 m 2. A crawl space encapsulation otherwise known as a sealed crawl space is a better alternative to vented crawl space which provides the following functions. But its easier said than done.
The main thing to take-away. The crawl space floor area must be completely sealed with a vapor-retarding material. As an added benefit the conditioned crawl space can provide climate-controlled storage space.
Air from the crawl space rises and flows up into your living spaces. Air quality drastically improves inside the home once the crawl space vents are sealed. Properly sealing the crawl space and removing the moisture from the ground and air is part of the solution that helps provide a mold-free and insect-free environment which leads to a more energy-efficient and healthier home says Waltz.
All crawl space walls must be insulated to appropriate R-values for the regional climate. The answer is all in the moisture and humidity levels. About 50 of the air you breathe on the first floor comes from the crawl space.
To protect your crawl space a closed or encapsulated crawl space is now preferred to an open or vented crawl space. Having a sealed crawl space will prevent the buildup of moisture which can lead to mold mildew and other health concerns. Along with insulation a sealed crawl space can give the homeowner around 18 in savings for heating and cooling costs.
They should provide a minimum of 1 square foot of vent area for every 500 square feet of crawl space area. In an unvented crawl space plastic sheeting seals the ground and keeps most of the soil gases out of the air. An unvented crawl space or better yet no crawl space.
In humid climates vented crawl spaces dont make sense because they increase moisture problems. And because we all know how hot and humid summers in the Midwest can be its likely that a closed or encapsulated crawl space is the best solution for your home. They reduce the opportunity for condensation to form on cold floor or rim joists from humid air entering through the vents.
When crawl space air rises replacement air which consists of outside air comes through the crawl space vents. A good vapor retarder on the crawl space floor is essential to the success of most crawl spaces. Jesse Waltz a foundation engineer votes to seal off crawl space vents altogether.
If designed properly an unvented crawlspace in a house in the eastern United States is drier than a vented crawlspace. Unless the floor between the house and crawl space is totally sealed with polyurethane foam then the building occupants will breathe some air from the crawl space. Its obvious to homeowners with basements that water intrusion is a problem.
Overall while a sealed crawl space might not be as well known as a vented crawl space they provide a number of additional benefits to your home. In this Energy-Smart Details article senior editor Martin Holladay explains how to create a sealed crawlspace. The air-circulating device must move at least 1 cubic foot of air per 50 square feet of crawl space area.
It also protects pipes better from freezethaw cycles and requires less insulation. Encapsulated crawl spaces are consistently better at controlling moisture that enters from the damp earth or from warm humid air that would otherwise intrude from the outdoors. Replacement air also seeps in through leaks in the joists and other unsealed areas.
All water or moisture sources must be dealt with. If the ground is covered with an approved Class I vapor barrier and the vents are situated to provide cross ventilation the requirement becomes 1 square foot of vent for every 1500 square. Common Crawl Space Problems.
Vented crawl spaces dont really work as promised. Some of the structural alterations that will be done to convert a vented crawl space to a closed crawl space involve sealing vents and installing a sealed vapor barrier on the crawl space floor. The seams must be sealed.
The crawl space should be constructed such that vents can be installed on at least 3 sides. It would be nice if all the seams of the plastic were welded together and all the edges were caulkedsealed to the foundation. Prevent water vapor entry with a sealed liner sealing methods can vary in quality and are pertinent to the life of the system Condition and monitor the sealed crawlspace via ducted dehumidifier and indoor humidity meter.
Sealing off the vents insulating the walls and covering the ground with a vapor barrier that is sealed to the walls also helps to reduce potential moisture problems by keeping out humid outside air and moisture vapor from the ground. Weve discussed how air from the crawl space gets into the home and what can be brought along with it when that air is substandard. The crawl space is the lowest point of your home.
Today crawl space science looks a lot different. This moisture barrier is extended up the interior foundation walls of the structure. Provide a method of removal of water intrusion via sump pump or drain to outdoors.
The edges of the vapor retarder must be lapped up against the inner foundation walls. There should be vents on all crawl space walls.