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All basements are subject to high humidity and moisture levels, especially between Spring and Autumn.  Typically, basements are mostly below the ground level.  Therefore, basement foundations and floors are in constant contact with damp soil.  Moisture will typically transmit through these surfaces by way of capillary action, commonly referred to as moisture migration.

This condition is indeed expected and can be controlled by exercising some simple remedies. However, if low relative humidity and/or moisture content in the basement space is required for specific or special purposes, remedial action can be very expensive. 

The following recommendations will assist to reduce high humidity and dampness levels in basements:
  • Cold stroage rooms must be natrually ventilated either with an operating window or a wall vent.
  • Install an exhaust fan in the basement bathroom or shower.
  • Avoid storage of materials directly against unfinished foundations walls or unfinished basement floors.
  • Too much storage of material in a basement, or overfilled closets, will impede air circulation.
  • A small room fan could be operated to encourage proper air circulation.
  • Ensure that all spaces in the basement are ventilated. Undercutting of closet doors, cabinet doors and installing wall grilles may be required in the storage areas.
  • Seasonally disconnect your central humidifier (in April, if attached to your furnace).
  • Position a dehumidifier in a central basement location and operate continuously.
  • Open basement windows whenever possible to allow for a natural air change.
  • Leave the furnace fan on continous operation in houses with a forced-air heating system. Ideally, return-air inlet grilles should be installed low on the wall in a central location. 
  •  WARNING:  For Mold and other health issues please contact
                                                  MIKE BULLER
                                  Greenough Environmental Consulting
                                      1827 Woodward Drive, Suite 110
                                                  Ottawa, Ontario