Why moisture is the key to home energy efficiency

February 19, 2014
  |   1 Comment

Home energy efficiency is often dominated by discussions about cooling and heating. After all, heating and cooling (including water heating) account for about 60% of energy expenses in the average single-family home. Yet the discussion often neglects an important factor in home comfort and in heating and cooling usage: moisture.

For example, most people will feel cooler in a room at 75˚F and 25-percent relative humidity than in a room at the same temperature with 40-percent relative humidity. Rooms with higher relative humidities feel warmer, so occupants are less likely to raise their thermostat setting in winter when they have a healthier level of humidity.


Optimal Moisture

Optimal moisture levels depend on many factors: time of year, regional climate, ventilation, vapor barriers, home-heating type, and more. During the summer, optimal indoor moisture levels are between 30 and 40 percent.

There are many problems associated with high or low levels of moisture in a home. Homes that are too “tight” (that is, homes that trap moisture inside without accounting for humidity) can lead to costly mold and indoor air quality issues. Homes that are air-tight, like Passive Homes, employ a vapor barrier and a mechanical, balanced ventilation system with heat recovery that addresses both air-quality and comfort issues by continually exchanging indoor air.


Image of moisture and mold in a bathroom

Excessive moisture can cause mold.


Quick & Easy Tips

  1. Make sure your water spouts point away from your exterior walls, and that your home’s landscaping slopes gently away from your home.
  2. Cover dirt floors in the crawl space or attic with a 6 millimeter poly to mitigate moisture issues.
  3. Speak with a home energy auditor who can give you specific recommendations about humidity based on your home, budget, and climate.
  4. Make sure your roof and attic keep water out of the house. If there is moisture buildup on the cold side of the home, take preventative weatherization measures to ensure moisture isn’t penetrating building materials.
  5. Ensure your home is properly ventilated with exhaust fans in key locations like the bathroom and kitchen. Today’s exhaust fans often produce very little noise, remove odors and pollutants from rooms, and can address humidity levels in the whole house. Make sure that vents lead directly outdoors, and that they don’t vent into the attic or another enclosed space.
  6. Get a properly sized A/C unit. Oversized air conditioners can lead to rapid cooling without addressing humidity levels. That leads to problems with high relative humidity.

Remember, some humidity is important. Contact a home energy professional to best understand your home’s humidity levels and what you could do to improve them.


By David Zussman, Marketing Coordinator, Elysian Energy, a Montgomery County Certified Green Business

Logo of the Certified Green Business program


One comment on "Why moisture is the key to home energy efficiency"

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