Many homes have musty moldy smell. Inside the home appears to be dry; the floors look good, walls are clean, the windows are clean, the heating and air system is working. So, why are there odors in the crawlspace?
Very few people have ever entered their crawlspace.
What we find more often than not when entering a crawlspace is – Open soil, fallen installation, pooling water, mold starting to grow on wood surfaces such as floor joist in subflooring, condensation on the heating and air-conditioning system in air ducts.
The musty odor inside the home is from the crawlspace.
Each problem noted above contributes to the odor.
Open soil is the largest contributor to elevated humidity and odors. Open soil can breathe up to 15 gallons of water into the air into a 1400 square-foot crawlspace every day. Also open soil breathes gases into the crawlspace and then into your home. The best known soil gas is Radon. Radon is a dangerous gas but because it is odorless we are not as concerned with this gas when trying to eliminate odors. There are an unlimited number of soil gases because depending on where your home is located, the soil composition will create a variety of combinations of different so gases and different odors. Any open soil is not acceptable when your goal is reducing odors and creating better indoor air quality.
Subflooring crawlspace insulation. Insulation placed between the joists in your crawlspace is like placing a giant fiberglass filter under your home. The first couple of years, the crawlspace insulation may be helping prevent odors by trapping moisture and absorbing odors, thus preventing those odors from reaching you. This is temporarily, since once the insulation has filled with odors, the odor start to enter the home . The moisture eventually starts to make the insulation fibers fall, the insulation become stringy and often falls down from the floor joist. Not only does crawlspace insulation eventually increase odors but is invaluable as an insulation product because most crawlspaces are about 60 to 65° most of the year.
Standing water promotes bacteria algae and slime molds. As the water of evaporates the water molecules carry the foul odors upwards into the home. The water molecules in the air also elevate the moisture content and feed active mold growth on porous items such as wood joist and subfloor.
Standing water, even in small amounts, is never acceptable when considering indoor air quality.
When you see mold on wood in a crawlspace, you know that the crawlspace has experienced elevated moisture conditions and or water problems. Mold is a secondary problem to an underlying moisture problem. If mold is allowed to stay on the wood long enough, it will start to digest the wood this is what is commonly referred to as rot. Elevated mold counts inside a home are a health concern. Most people don’t realize how their crawlspace directly impacts the living space above.
When you find condensation on air ducts, it is a condition of too much humidity within the crawlspace. Many people have doubled the insulation on the air ducts and condensation still occurs. Until the underlying moisture and then humidity is lowered the condensation will not stop. We have found many heating and air-conditioning units that have rusted to the point of failure before people realize they had too much humidity and that the condensation was a problem. Humidity problems with in a crawlspace can literally take years of life away from the heating and air-conditioning system.
How is the air in the crawlspace getting into my home?
Pathways from the crawlspace inside the home are many. During construction many holes were drilled in the subflooring and the framing to run wires cables and water pipes. These holes should be caulked, but usually are not. Under bathtubs and showers larger areas are left open for drains, usually 12″ x 12″. The air ducts are not sealed 100% and duct leakage allows the crawlspace hair in and out of the living space. It is nearly impossible to block up all of the pathways that the crawlspace here maybe entering the home, but by sealing up as many of the large holes as possible you will stop some of the cross contamination and make the home more energy-efficient.
When you have elevated moisture humidity or pooling water it provides the habitat to grow bacteria algae and molds. These contaminants combined with soil gases will make a combination of odors from musty to sour to a dead animal like smell.
What should be done?
Remove the bulk water. Others install French drains on the exterior of the home or french drains in the crawlspace with a sump pump. Then install a quality heavy duty moisture barrier that will block moisture from all of the open soil, cover all of the piers, and cover all of the crawlspace walls below grade. Lastly, install a dehumidifier that is designed to be used in a crawlspace and will keep the crawlspace humidity to less than 55%.
If you have a gas furnace, make sure you have enough make up air for combustion.
This base plan is very simple but can be complicated to complete in the real world under a home. Working in a crawlspace is most similar to working in a coal mine. Imagine working under your dining room table for days trying to change environment.
Each crawlspace is somewhat different and a good evaluation and scope of work from a qualified company is the first step in making sure you have a healthy crawlspace and a healthier environment within your home.