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Build Tight, Ventilate Right
by Steve Gramins

Most people intuitively know the importance of fresh, clean air for continued good health–it is an integral part of our well-being. However, unlike Flying Hawk or even our parents and grandparents, we spend a great deal of time inside buildings sealed increasingly tight for energy efficiency. Unfortunately, these buildings are also very efficient at trapping bad, stale air. A health hazard results because indoor air can be up to ten times more polluted than outdoor air, and we are exposed to it for longer periods of time.

The solution is proper ventilation, on which we've relied for hundreds of years. Technological advancements along the way have mechanized the ventilation process, creating a trustworthy system that maintains healthy indoor air without sacrificing energy efficiency.

Ventilation is accomplished by the random infiltration of air through porous building materials and open windows. In homes built as little as 15 years ago, full air exchange occurs approximately every hour. However, research indicates that in newer homes with more advanced construction materials, full air exchange occurs only every 5-6 hours. This rate of exchange does not meet the standards set forth by the American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE), which recommends a minimum of .35 air exchanges per hour. In other words, in one hour, 35 percent of a home's air should be exhausted and replaced with fresh outdoor air. Testing proves that only mechanical systems provide outdoor air reliably through all seasons.

One product that effectively provides proper ventilation for the home is the balanced mechanical ventilation system. This system is designed to exhaust warm, stale air from major pollutant sources such as kitchens, laundry rooms and bathrooms, while at the same time bringing in an equal amount of fresh air to prevent any pressure build-up within the home. The mechanism works well because it allows for an even, balanced, controlled and continuous distribution of fresh air.

There are two types of balanced mechanical ventilation systems—heat recovery and non-heat recovery. The difference between the two systems lies squarely in the names. The heat recovery ventilation system uses a heat exchanger to warm the incoming air. The incoming and outgoing streams of air are passed through the core of the exchanger, where heat from the exhausted air is transferred to the cooler incoming air. Thus, fresh air supplied to the home is pre-heated, eliminating the need for a separate air heater, a necessary component of the non-heat recovery system.

Looking for more? The following resources offer information about ventilation, indoor air pollution and indoor air quality products: U.S. Department of Energy—Energy Efficiency and Renewable Energy Network Air Infiltration and Ventilation Centre Research Products Corporation (800) 545-2219 WEB Products, Inc. (800) 875-3212

Of course, there are several things to consider before installing a balanced mechanical ventilation system in your new home. The climate in which you live or intend to build should factor into which type of system you choose. A heat recovery ventilation system is more helpful in a colder climate than in a warmer one; there's no need to heat incoming air when it's already warm outside. Installation costs should also be considered, as should operational and servicing costs. In older homes, a mechanical ventilation system may be difficult, costly and time-consuming to install due to a number of factors.

Take time to consider the importance of air quality in your home. Research how effective a whole-house ventilation system will be for your home, new or existing. Recall the words of Flying Hawk about the importance of fresh air. Then stay true to the age-old adage: build it tight, and ventilate it right.

Sources: A Guide to Energy Efficient Ventilation, summarized by Martin W. Liddament; Air Infiltration and Ventilation Centre; David Pearson, The New Natural House Book. Fireside/Simon & Schuster, 1989; "Mechanical Ventilation for the Home," Don Stevens, Home Energy Magazine Online March/April 1996; Therma-Stor Products.