Avoiding Mold Growth in Buildings by Controlling Moisture
Control moisture and keep materials dry to avoid mold problems.
TO FIND HUMIDITY & MOISTURE PROBLEMS:
- Watch for condensation on windows, especially if on double-glass.
- Use a relative humidity meter (hygrometer) to see if you have excess humidity.
- Use a moisture meter to find damp spots in ceilings, walls, floors.
- Look for wet or stained surfaces, under basement carpets, or behind baseboards.
- Sniff for moldy or damp odors near carpets, or in air leaking in through cracks.
TO REDUCE MOISTURE CONDENSATION:
Avoid condensation that forms when warm, moist air contacts a cold surface, by:
- Open windows for fresh air to enter, especially bedrooms overnight.
- Increase attic and crawl space ventilation: uncover blocked vents.
- Vent exhaust fans and clothes dryers to outdoors (not into attic or crawl spaces).
- Use exhaust fans when showering (and after), steaming, or cooking with gas.
- Wire fans to run more often with a shut-off timer switch, with the light switch, best with a dehumidistat, or continuously (can be smaller and quieter).
- Connect clothes dryer exhaust vent securely to outdoors; keep vents clean.
- Install filtered fresh air entry vents in downstairs closets for makeup air to enter from outdoors when exhaust fans operate, instead of up through the floor.
- Keep furniture and clothing a few inches away from exterior walls.
- Run a dehumidifier in the dampest problem areas, like basements.
TO STOP MOISTURE PROBLEMS:
- Find and stop any leaks from plumbing, rainwater, or groundwater.
- Dry and clean up after any flooding or leaks.
- Waterproof bathtub/shower tile grout, building envelope, and concrete below grade.
TO IMPROVE DRAINAGE:
- Pipe furnace or cooling coil condensate drainwater outside the foundation.
- Drain the downspouts well away from the building, best to storm sewer.
- Clear drains in the basement, crawl space, and outdoors.
- Dig a groundwater collection and drainage pipe below the foundation footing.
- Cover outside the basement wall with a sealer coating and a drainage membrane.
- Slope soil away from the house.
TO AVOID MOLD GROWTH:
- Wipe condensation from windows, and ventilate more.
- Dry or replace water-damaged carpets and building materials quickly.
- Dry all cellulose products (paper, cardboard, wallpaper, ceiling tiles, wood, carpeting) indoors, and remove such debris from the crawl space.
- Clean cooling coils and condensate drain pans in air conditioners, dehumidifiers, and refrigerators annually.
- Do not use a humidifier (moisture helps mold grow).
- Clean any salt “efflorescence” from masonry to help it dry.
- Remove carpets, and cover concrete floors with a vapor barrier of paint, plastic sheet, or vinyl flooring, then perhaps finish flooring.
- Avoid unglazed clay pots. Replace the top inch of soil annually.
TO AVOID MOLD IN A BASEMENT:
- Add a pint of water, then 1/4 cup of mineral oil to basement floor drains annually.
- Waterproof, ventilate, and heat the basement before finishing it below ground level.
- Operate a dehumidifier if needed to keep humidity below 60%.
- Raise stored items off a concrete floor.
- Avoid placing objects that block air flow near concrete or damp walls.
TO AVOID MOLD IN A CRAWL SPACE:
- Cover all exposed soil with black plastic sheets.
- Seal penetrations from the crawl space through duct joints and floor.
- Keep crawl space perimeter vent holes open and screens clear.
- Dig soil 8 inches below crawl space vents and wood siding.
TO CONTROL AIRBORNE MOLD:
To control mold and other fine dust particles that are indoors:
- Vacuum clean carpets often, with ventilation/filtration running or windows open.
- Use washable floor mats or rugs in entryways and other traffic areas.
- Filter dust particles out of the air, especially when there is much activity.
- Use high efficiency pleated filters that fit well in the furnace cold air return.
- Switch the thermostat to get continuous air flow often, even when not heating.
- Use portable air cleaners with good filters in areas where you spend much time.
NEXT: 6. Mold Cleanup
©2004-2019 Richard Knights, Blue Sky Testing LLC
Salem, OR & Seattle, WA, http://www.inyourair.com