Crawl Space Drying >> How To Prevent Mold In Your Crawl Space

Conditioned crawl spaces perform better than vented crawl spaces in terms of safety, health, comfort, durability and energy consumption. Conditioned crawl spaces also do not cost more to construct than vented crawl spaces. Existing vented crawl spaces are experiencing serious moisture and mold problems and are costing builder's and How To Prevent Mold In Your Crawl Space homeowners significant  resources to repair. 

Despite the obvious problems with existing vented crawl spaces and the obvious benefits of conditioned crawl spaces there is not a significant trend towards the construction of conditioned crawlspaces. How To Prevent Mold In Your Crawl Space One of the reasons typically cited by builders and designers is "the code does not allow me to build unvented crawl spaces". 

This is both generally correct and misleading. The model codes do not allow the construction of "unvented" crawl spaces – except in very limited circumstances, but they do allow the construction of "conditioned" crawl spaces. How To Prevent Mold In Your Crawl Space The distinction is important and necessary. 

Background Crawl space venting is generally viewed as good practice despite the obvious moisture problems that occur when outside air with a dew point higher than interior crawl space surface temperature is permitted to enter a crawl space. How To Prevent Mold In Your Crawl Space Unvented, conditioned crawl spaces with insulation on the perimeter solve this problem. 

Unvented, conditioned crawl spaces with insulation on the perimeter perform better in terms of safety and health (pest control), comfort (warm floors, How To Prevent Mold In Your Crawl Space uniform temperatures), durability (moisture) and energy consumption than passively vented crawl spaces with sub floor insulation. 

Perimeter insulation rather than floor insulation performs better in all climates from an energy conservation perspective. How To Prevent Mold In Your Crawl Space The crawl space temperatures, dew points and relative humidities track that of the house. Crawl spaces insulated on the perimeter are warmer and drier than crawl spaces insulated between the crawl space and the house. 

Cold surfaces that can condense water are minimized when crawl spaces are conditioned. Crawl spaces should be designed and constructed as minibasements, part of the house – within the conditioned space. How To Prevent Mold In Your Crawl Space They should be insulated on their perimeters and should have acontinuous sealed ground cover such as taped polyethylene. 

They should have perimeter drainage just like a basement when the crawl space ground level is below the ground level of the surrounding grade. Constructing Conditioned Crawl Spaces Crawl spaces should be designed and constructed to be dry. How To Prevent Mold In Your Crawl Space A dry crawl space is less likely to have pests and termites and mold. 

A dry crawl space is therefore safer and healthier than a wet crawl space. Crawl spaces must control rainwater, groundwater and provide drainage for potential plumbing leaks or flooding incidents (Figure 1). How To Prevent Mold In Your Crawl Space Crawl spaces must always have a drying mechanism. 

One of the most effective ways to provide a drying mechanism to a crawl space is to condition a crawl space by heating and cooling the crawl space as if the crawl space is included as part of the home. How To Prevent Mold In Your Crawl Space Crawl spaces must always have a ground cover that prevents evaporation of ground moisture into the crawl space. 

There are many ways to provide a durable ground cover or liner. Most effective is 6 mil sheet polyethylene that has taped/sealed joints and that is attached to the crawl space perimeter walls. How To Prevent Mold In Your Crawl Space This ground cover must be continuous through piers and supports. Crawl space perimeter walls should also be insulated. 

When insulating crawl spaces internally (as well as basements) it is important to not leave concrete or masonry exposed in order to control condensation. It is similarly necessary to control condensation at rim joist areas. How To Prevent Mold In Your Crawl Space This is best done using rigid insulation installed either externally to the rim joist or internally against the rim joist. 

In warmer weather, a sealed crawl space prevents warm air from entering through wall vents and condensing on surfaces cooled by the ground temperature inside the crawl space. How To Prevent Mold In Your Crawl Space Sealing also produces energy savings by preventing the loss of dryer conditioned air (or during winter months, warmer conditioned air) that has been supplied to the space. 

Ventilation openings should not be installed in the crawl space walls (except when an active exhaust fan is located in the wall to provide mechanical ventilation, described below). How To Prevent Mold In Your Crawl Space In addition, the following locations must be air-sealed using caulks, adhesive, air-sealing foam, gaskets or adhesive membranes: Exterior entry hatches or doors. 

Joints between the top of the foundation wall and the mud sill, between the mud sill and the rim joist and between the rim joist and the sub-floor. Around ducts, pipe conduits or other penetrations through the wall or rim joist. How To Prevent Mold In Your Crawl Space Foundation walls may be insulated on their outside, inside or, in the case of insulated concrete forms, both sides. 

Insulating on the outside keeps the foundation wall's temperature and moisture content more uniform throughout the year. How To Prevent Mold In Your Crawl Space If insulation is applied to the interior side of a basement wall, materials that can act as vapor barriers (e.g., polyethylene film, foil-faced paper or vinyl wall covering) should not be used. 

The vapor barrier can trap any moisture present in the foundation wall, creating moisture and mold problems on the wall's interior surface. How To Prevent Mold In Your Crawl Space Moisture and humidity issues are not eliminated once the crawl space is sealed. In the sealed environment, a small amount of moisture or humidity can cause a significant moisture problem.

Unless provisions are made for some level of air exchange with conditioned air. How To Prevent Mold In Your Crawl Space This is accomplished with mechanical ventilation of the crawl space in essentially two ways: An exhaust fan inserted into the crawl space wall removes a small amount of air from the crawl space.

It is replaced by drawing a small amount of conditioned air from the living space (through cracks and other openings in the floor above into the crawl space). How To Prevent Mold In Your Crawl Space If radon-resistant construction is necessary (see), do not implement this option because it can interfere with the operation of the mitigation system. 

A small amount of conditioned air (minimum 1 cfm per 50 sq. ft. of crawl space floor area) is blown directly from the heating and  How To Prevent Mold In Your Crawl Space air-conditioning system (from equipment located in the living space above and ducted to the crawl space, or directly from HVAC equipment located in the crawl space).

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