Q: I have a cottage on Lake Huron that has a musty smell I cannot track down. It is bad enough that when you walk up to the home, you can smell it through the door before entering. In fact, after spending a weekend there, everything reeks of it, including clothes, bags and hair.
The crawlspace is dry, covered with clear plastic sheeting. There's no mold or mildew growth on either side of the sheeting, nor on the block walls, joists, floorboards or beams. I also had additional foundation vents installed that I open in the spring and close in the winter.
The home is used only during the summer, on the weekends. It is not heated, so all the lines are drained and winterized until spring.
Is it possible that moisture is moving through the crawlspace? Is it possible that there is an improper amount of air movement in the interior during the winter and on summer weekdays? Because of the A-frame design, there are no roof vents, nor any way to install them.
A: The problem with any unattended structure is moisture buildup, which leads to the musty odors you are experiencing. Though mold and mildew are not present on the visible interior surfaces, odor-causing microbes may be inside the walls or ceiling. When the home has no heat source, moisture left over from the previous summer's humidity will condense inside wall and ceiling cavities and become trapped and stored in the insulation.
Trapped mold spores are dormant during cold months but begin to grow and release odors with warmer weather.
1. Open the foundation vents in the winter when the outside air is dry. This will release moisture from the crawlspace to the outside air. When the home is winterized, there is no chance water pipes in the crawlspace will freeze. Close the vents in the summer to keep out the warm, humid air.
2. In cooler climates, air conditioning is not a necessity, however, air conditioning also lowers indoor humidity levels. Use a dehumidifier in the warmer months to reduce the moisture levels inside the home.
3. In the winter, place open bags of charcoal or sidewalk chalk wrapped in cheesecloth at various locations inside the home. The charcoal or sidewalk chalk will absorb moisture and odors. You also can use open boxes of baking soda, but this might become an expensive fix. You can use commercial products such as Damp Rid, but in my experience the water that collects in the container can be acidic. Do not leave it open around children or pets.
4. Air movement is vital to removing moisture and odors. A ceiling or bathroom fan can be fixed to a timer to operate about 12 hours a day.
If following these suggestions fails to remove the odors, then it's time to have a home inspector check for moisture on insulation in the wall and ceiling cavities.
The home inspector will use a moisture meter to probe the walls and ceiling. In rare cases, you'll need to remove portions of the wall covering for the inspection. A home inspector is not a contractor, so any invasive inspection openings will need to be repaired by a qualified contractor. Find qualified home inspectors at http://www.ashi.org.
(Dwight Barnett is a certified master inspector with the American Society of Home Inspectors. Write to him with home improvement questions at C. Dwight Barnett, Evansville Courier & Press, P.O. Box 268, Evansville, Ind. 47702, or email him at d.Barnett(at)insightbb.com.)