11/15/2012 9:59:00 PM GREEN BUILDING Poor sealing, insulation can cause a host of problems
PAUL SCRIVENS Green Home Energy Advisors
Question: My energy bills are high, and my home is always cold and drafty. We have condensation on windows, mold and mildew on surfaces and a smell of dampness. Insects are a problem and I keep getting electric shocks. What could be the cause?
Answer: All buildings continuously lose energy in the form of winter heat loss and summer heat gain, and that heat and cooling loss needs to be continuously replaced by your heating and cooling system. This primary energy loss comes from poor insulation, and outside air infiltration through holes in the home's envelope. In reality, up to 40 percent of a home's energy can be lost through air and moisture leakage.
Air leaks are driven by air movement based on air pressure and temperature differences. The earth's atmosphere is continuously changing with low- and high-pressure systems building and declining.
As they do, air movement equalizes pressure in the form of wind. As wind hits a building it creates a high-pressure point, and the opposite side becomes a low-pressure point; holes in the building envelope leak air into and out of the structure, causing drafts and temperature differences.
As temperatures rise in a building the air expands, volume increases and pressure drops; as temperatures drop the reverse is true.
Therefore warm air always rises and cool air sinks. In winter warm air rises and leaks out of a building at high elevations; as it does, cold air replaces the warm air through lower level leaks causing drafts. In summer the process reverses. As an example, a typical home not designed for low leakage leaks around 143 cubic feet of air a minute.
Leaks not only waste energy through air infiltration, they also allow moisture, insects, dust and pollutants to penetrate internal cavities. Moisture vapor molecules are lighter and smaller than air and can go where air cannot. In cold climates the outside air can condense in walls and the attic causing moisture damage. This moisture damage reduces the effect of insulation; it also encourages mold, mildew and fungi buildup that can create health problems for occupants.
Other effects of leakage include internal humidity changes; in cold climates excessive leakage will dry out internal air. This happens as internal warm moist air is replaced with outside cold dry air. A common effect of dry air is static electricity and personal electric shocks when touching grounded electrical appliances. When the cold incoming air is wet it creates condensation buildup on walls and in the attic causing rot and bacterial damage. In summer the opposite exists: The cool dry air is replaced by incoming warm moist air and the hot sticky humidity effect increases; putting more stress on an air conditioning system to remove the heat and the humidity.
When considering energy conservation and living comfort, the air that is being forced in and out of a home through leaks due to wind and convection should be prevented. Sealing a home effectively with an air and moisture barrier will significantly reduce both winter and summer energy losses, improve occupant comfort, significantly reduce pollutants and keep out pests and noise.
Visit www.energystar.gov/index.cfm?c=home_sealing.hm_improvement_sealing for more information.
Paul Scrivens operates Prescott-based Green Home Energy Advisors. Contact him through www.greenhomeenergy advisors.com.