As we have learned from previous blogs, homes that feature crawl spaces often suffer from moisture damage related to the crawlspace environment.  Your crawl space is sucking up moisture from the ground and your home is sucking up moisture from the  crawl space.  As you know, bad things happen to your house when you mix moisture and wood.  Since indoor airflow naturally drifts upwards, we will show you how using a vapor barrier and a dehumidifier in your crawlspace will significantly reduce the amount of moisture in your home.  This slowly traveling moist air carries with it mold and other harmful particles.   One of our Dri-CrawlSpace^® dehumidifiers has more than enough power to dy out any mold and prevent more from infiltrating your home.  Further down this article, you can read other additional practices that anyone can do to help reduce humidity in the home.

There are four balancing factors that dictate a home’s moisture balance: source strength, temperature, moisture transfer rate and circulation-ventilation rate. If you have a major problem with any of these four factors, you are pretty much guaranteed to have moisture problem in your home.  Identifying a problem basically requires determining if there is a constant source of moisture such a roof leaks, gutter and downspout problems, damp foundations and flat property with inadequate natural drainage.  Source strength of moisture in a crawlspace is often as strong as leaking pipe or HVAC equipment or as mild as water vapor seaping up from underground.  Temperature differences also promote condensation.  Cool ground temperature always keeps your crawlspace signifigantly colder (and damper) than the living space above.  Using exhaust fans when cooking and showering helps reduce moisture and, all dryer vents should be vented outside.  Moisture transfer solutions include sealing all air leaks from vents, windows, doors, duct work and eliminating any puddles of water.  Doing this will ease the load for your crawl space dehumidifier.  The fourth and final factor is the circulation-ventilation rate.  This refers to the rate of fresh, dry air entering the home and flowing through it.  Any areas where air does not move freely can become moisture pockets.  In most geographic areas, fresh outside air is not dry and tends to worsen the humidity problems when it enters the home.  That’s where a crawlspace dehumidifier can save your home.

Optimally, you want to keep the relative humidity level in your home between 30% and 50%.  Ideal crawlspace humidity is 30% - 40%.  In the upper floors, it is ok if the humidity approaches 60%.  It is important to seal the ducts and vents because leakage in the crawlspace can cause pressure imbalances in the crawlspace and house.  Duct leakage allows air to be pulled through openings into the house due to the house pressure becoming negative with respect to the crawlspace.  This air brings with it mold spores and other contaminants that negatively affect your indoor air quality. Many times water gathers in crawl spaces from run-off from improperly graded soil.  The grade should be sloped away from the foundation at least 5%.  Inspect the gutters to make sure they are free of debris and that the downspouts empty 8 to 10 feet from the foundation.  If you’re using vents, trim back any dense shrubs that may be blocking natural ventilation.  Check for leaky plumbing; plumbing leaks can be a primary source of crawl space moisture.

Once you have properly secured your home from the sources of excessive moisture, building a vapor barrier, sometimes called a "vapor diffusion retarder" (VDR), in your crawl space is the next step.  Before you begin constructing your barrier, it is vital to remove all standing water and to clean up any mold that may be present in your crawlspace.  If you have standing water, a shop-vacuum may do the job.  If you have a large amount of water, you may need to place a dehumidifier in the crawl space for several days prior to clean-up.  Place one of our Dri-CrawlSpace^® brand Crawlspace Dehumidifiers on a piece of plywood or cinder block to keep it off the naked ground.  Run your drain hose out the vent and away from the house.  Make sure your hose is gradually sloping downward for the entire length.  The water drains by gravity and cannot go up, over an obstacle.  When the crawl space is sufficiently dry, you may begin cleaning. Depending on how much moisture there is and how dirty your crawlspace is, you may want to wear cheap, throw away painters jumpsuits to protect your clothing.  If a large amount of mold is present, you should at least wear a paper dust mask to prevent inhalation of mold particles that may make you sick.  We recommend using a dust respirator mask with replaceable filters.

When removing mold, you should also wear rubber gloves and eye protection because you will be handling caustic chemicals.  Respirator masks are available that filter dust and gaseous chemicals.  Remember, you will be in a confined space with little air circulation.  Take appropriate safety precautions.  Read all labels and instructions carefully when using chemical cleaners.  Never mix liquid chlorine bleach with ammonia or other household cleaning products.  This could result in the production of hazardous gases.  A good mold and mildew cleaning solution for wood, vinyl and aluminum siding is: one third cup of laundry detergent, one quart of chlorine bleach and three quarts of warm water.  Sponge vigorously all contaminated areas thoroughly and completely.  Let the area dry and use an air freshener if mildew smells persist.  When you are certain all mold is removed and your crawlspace is dry, tightly seal all spaces, cracks and openings with plastic, caulk, spray foam, flashing, etc.  Make sure all air ductwork and vents are properly sealed to eliminate humid air from entering the crawl space.  Mold can be found in the ductwork of cooling and heating systems.  Sometimes there are air leaks in the ductwork, allowing moisture to gather, where mold and mildew can grow.  Check your filters regularly because mold can also grow on dirty air conditioner and furnace filters.

Repairs to hardwood floors damaged by moisture can be very expensive.  EPA suggests spraying icynene insulation on the wood under toe space grilles in the crawlspace to help stop condensation and seal the wood.  Icynene foam insulation provides both insulation and an air barrier…

A vapor barrier is used to prevent the penetration or movement of moisture from one area to another.  It acts as a physical shield that repels moisture and keeps it from entering enclosed cavities of your home.  Vapor barriers must be continuous to be effective. Cover the entire crawl space floor with 6-8 mil polyethylene (plastic) sheeting and overlap all seams two feet and seal with duct tape.  Extend the outside edge of the plastic sheeting up the foundation wall at least six inches above the grade.  Seal the plastic to the foundation wall with concrete tape, construction adhesive or a pressure-treated nailing strip.  The vapor barrier on the insulation should be placed against the heated side or the sub-flooring. The polyethylene sheeting should be layed over the crawlspace soil with a minimum of joints.  It is recommended that you have your crawl space dimensions cut from a roll of plastic rather than using many pre-cut sheets that have to be joined together.  As an additional step, one or two inches of sand or gravel may be placed on top of the polyethylene.  The sand or gravel weighs down the vapor barrier, preventing condensation on the undersurface while absorbing the water droplets that may condense off the top surface.  This also protects the plastic from tearing when you walk on it in the crawl space.

Some contractors sell an encapsulation system that includes what we have described above, plus a mold inhibiting paint job, and an extra thick, 7 layer, 20 mil vapor barrier.  Unless you plan to entertain tea parties in your crawlspace, we feel this system is excessive and often an unnecessary expense when it comes to controlling humidity and indoor air quality in your home.  All joking aside, compare the average cost of an encapsulation system of $12,000 to installing a basic vapor barrier (using inexpensive supplies from a local home improvement store) and installing one of our heavy-duty Dri-CrawlSpace^® brand Crawlspace Dehumidifiers.