Out with the Bad Air, In with the Good
With the escalation of fuel costs and the nationwide campaign to conserve energy, many Alaskans are taking advantage of the bargain basement rebates being offered to tighten up and insulate their houses.
In recent months, however, it has begun to leak out from the media that there may be more to the matter than meets the pocketbook. The one item that has received the most attention is that, in tightly enclosed areas with no air circulation, formaldehyde fumes arising from construction materials and insulation may reach toxic levels.
Other undesirable pollutants are cooking fumes, carbon monoxide and cigarette smoke, to name but a few. In addition, high humidity levels in tightly sealed buildings may lead to degradation of building materials and water or ice formation on windows and in insulation.
Given these precautions, the solution appears simple--merely provide adequate ventilation. But now we find ourselves in a Catch-22 situation. If we blow out the stale inside air and replace it with clean (and presumably cold) outside air, we have completely defeated our purpose for insulating and sealing the house in the first place.
The answer? Simple. Just install a heat exchanger. A heat exchanger works something like the radiator on a car or the plumbing in a refrigerator. In essence, they expel air from a building, but use part of the heat that it contains to warm the incoming air from the outside.
Professor John P. Zarling of the Department of Mechanical Engineering at the University of Alaska in Fairbanks has prepared a report for the State Department of Transportation and Public Facilities that explains the operation of such systems in detail.
Dr. Zarling makes the point that heat exchangers can recover sixty to seventy percent of the heat in the air expelled. He explains that, while well-insulated and sealed structures may exchange only ten percent of the air they contain per hour with outside air, some older structures may exchange as much as fifty to one hundred percent per hour. Clearly, in the latter case, a heat exchanger is not needed and would merely be an additional expense. However, in the tightly sealed house, humidity problems can quickly arise. For example, in a house of 2000 square feet which exchanges air at the rate of ten percent per hour, an input level of 0.38 pounds of water per hour would maintain a constant humidity level of 20 percent at 70°F. A single person, however, produces about 0.25 pounds of water per hour through breathing and perspiration. Only two people, therefore, would be sufficient to raise the humidity, and this does not even take into consideration activities such as washing or cooking.
The cost of heat exchangers, not counting installation, ranges from about $800 for commercially available models to about $250 for a build-it-yourself model for which plans are available.
