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Building Science by Norman Aceron Garcia

Condensation issues

by Norman Aceron Garcia

condensationCondensation, or sweating, accumulates on surfaces when the temperature drops below the dew point, which is the temperature at which water must be cooled to reach saturation. Components made of metal are typically the first places where condensation will form because of the metal’s characteristic thermal conductivity.

Condensation can be problematic as droplets can puddle and destroy building materials, like when condensed water recurrently drains from a water closet and deteriorates the washroom tile floor and subfloor. Elevated moisture encourages mould growth, which is a serious health risk. Leaking overhead pipes can be an extreme irritation in a finished basement, as they may destruct appliances, electronics, furniture and carpets. Pooled condensation can also cause electrocution of building occupants and electrical fire. Condensation typically forms in windows, plumbing drains, cold water pipes, water pressure tanks, and plumbing fixtures.

On the other hand, metals that are not in contact with cold water or air seldom show excessive condensation, even though it is unprotected from the same surrounding moisture-laden air. A water supply pipe that transports only hot water infrequently cools below the dew point temperature. Non-metal building materials that are in contact with cold water or air (such as plastic drains and piping) lack the thermal conductivity to become cold enough to trigger condensation. Metals also differ in their thermal conductivity. The metal’s capability to transfer heat and create condensation is approximately equivalent to its electrical conductivity.

Older homes often lack vapour barriers or sealers in the masonry and foundation, which is why condensation is commonly found in the basements of older buildings. The two approaches used to decrease condensation are to keep surfaces from becoming cold and to lower the relative humidity of the interior air. This can be accomplished by doing the following:

  • Turn on the exhaust fans when bathing and cooking. Leave it open for about 20mins after bathing or cooking to expel hot air and prevent it from condensing into walls and ceilings.
  • Ventilate the basement. However, this approach could be counterproductive if the indoor air is less humid than the outdoor air.
  • Use a dehumidifier. This simple and effective appliance can lower humidity because it condenses water vapour into its water tank instead of elsewhere.
  • Insulate cold surfaces such as water pipes and water pressure tanks with plastic foam wraps. Avoid using fiberglass insulation because it is useless when wet and it can be the cause of mould growth.
  • Remove plants from the home interior. Plants are a significant source of water vapour through transpiration of moisture.
  • Increase heat where condensation is a certain problem.

Be cautious that what seems to be condensation may actually be a water leak. Contact a qualified plumber if dehumidification and insulation don’t appear to fix the condensation problem. Condensation can lead to moisture-related problems that can affect structural components and your health.

Norman Aceron Garcia is a registered Professional Engineer and a Certified Property Inspector of Mr. Peg Property Inspections Inc. Please visit for more information on home inspection, building science and home maintenance tips.

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