The good news is that many of the measures that you can undertake to solve moisture problems can also save energy, thereby helping to pay for themselves. This section includes some examples. For further details, refer to one of the publications listed on page 11 of this fact sheet.
Reduce moisture sources inside the home
Getting at the source of excess moisture makes more sense than having to rely on a lot of ventilation. Ventilation removes moisture, but it also removes heat. Here are some tips on reducing moisture sources:
- Avoid drying clothes indoors. Vent dryers to the outside.
- Cover any exposed earth in the crawl space or basement with heavy polyethylene, sealed and weighted down.
- Slope soil away from foundations to keep the basement walls and slab dry. Patch any foundation leaks.
- Don’t use humidifiers, unless humidity levels are below 30 percent R.H.
- Avoid drying firewood indoors.
- Operate bathroom exhaust fans during a bath or shower. Use a range hood exhaust when cooking. Make sure fans are vented to the outdoors.
- Avoid steam cleaning carpets in winter.
Add insulation to cold surfaces
Areas that are un-insulated or poorly insulated – such as exterior corners or foundation walls – can be improved with additional insulation. This may be expensive by itself, but can be incorporated as part of a renovation. Don’t forget to install an air/vapour barrier (usually polyethylene) on the room side of the insulation to prevent hidden condensation behind the insulation.
1) thermal bridge at exterior corner in closet
2) add insulation (plus polyethylene and drywall)
Advisory
Some vermiculite insulation, which can be found in attics and walls of homes, may contain asbestos fibers. If you find vermiculite insulation in your home, do not disturb it and consult the Health Canada publication It’s Your Health – Vermiculite Insulation Containing Amphibole Asbestos by calling 1-800-O-Canada, or visit www.hc-sc.gc.ca.
Reduce uncontrolled air leakage
In the upper part of your house, air leakage outward carries moisture into the attic and wall cavities, causing long-term deterioration. In the lower part of your house, air leakage inward can chill window frames and door sills, causing frost to form. Air leaking in through foundation walls and the floor can be a source of moisture. Seal all cracks, joints and openings for services and around sump pump lids. It’s a good strategy to reduce this uncontrolled air leakage and rely more on controlled mechanical ventilation for fresh air. Seal hidden openings into the attic, tighten the attic hatch, weather-strip and caulk around windows and doors, install gaskets on electrical outlets, caulk baseboards and seal the top of foundations. (Natural Resources Canada has published another fact sheet of this series entitled Air-Leakage Control.)
Sealing air leakage into an attic
1) plumbing stack
2) attic hatch
3) electric wiring
4) tops of partition walls
5) electrical boxes
Install effective ventilation systems
If indoor humidity levels are high and moisture sources cannot be reduced any further, increase ventilation rates. Ensuring adequate mechanical ventilation is especially important if you are air tightening your home. Ventilation has the added benefit of improving your home’s indoor air quality.
Many older exhaust fans make a lot of noise but don’t move much air. Replace these with more efficient (and quieter! – that is, they produce less than 53 decibels or 2 sones when working) units and use them to remove moisture from bathrooms and kitchens. Make sure the air is being exhausted to the outdoors and not into your attic! Remember to check the ductwork from the exhaust fan – it’s usually hidden in the attic. The best approach is to provide a balanced ventilation system with a heat recovery ventilator (HRV). An HRV provides the opportunity for continuous ventilation without wasting a lot of energy by transferring heat from the exhaust air to preheat the fresh air.
Schematic of a ventilation system with an HRV
1) kitchen
2) living room
3) bedroom
4) cold-air return
5) fresh air
6) exhaust air
7) HRV
8 ) furnace
9) bathroom
10) laundry
Three additional points about ventilation are worth noting:
1) When outdoor conditions are mild and damp, such as in coastal areas or on a rainy day in the spring, ventilation will not be very effective at removing moisture because the outdoor air is saturated and has little drying potential.
2) A new house or newly renovated house needs lots of extra ventilation for the first year because construction materials – particularly wood and concrete – will be drying out.
3) Homes soak up moisture in the summer and gradually release it back into the air in the fall. To assist in “drying out” your house before the cold weather arrives, provide more ventilation and open up the windows on warm, dry fall days.
The use of air conditioners on muggy summer days can also help.
Clean and maintain mechanical equipment
Humidifiers, dehumidifiers, air-conditioning units and filtration systems can be a source of mould growth. Regular cleaning has the added advantage of improving the equipment’s efficiency.
To be continued February 1, 2012
http://oee.nrcan.gc.ca
