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Mark has been a teacher, lecturer and consultant to the green building industry for more than 25 years. He helps builders and manufacturers put building science to work, creating high-performance homes that are more durable, energy-efficient, cost-effective and more enjoyable to live in.
News from the Field

Monday, January 19, 2009

HVAC: Why Tight is Right

The goal of heating, cooling and ventilating systems is to provide an environment that supports our narrow band of comfort expectations: a conditioned air space with temperatures somewhere between 70 + 71 degrees F and a relative humidity of about 40%.

For an HVAC system to meet these exacting requirements, it is imperative that the building enclosure be tight. Yet if our goal is to improve indoor air quality, reducing the air change rate by building a tight home may seem counter intuitive.

The solution is a properly installed whole house ventilation system to continuously introduce the correct amount of fresh air, and dilute indoor pollutants such as the volatile organic compounds from carpet, stains and furnishings. We also need an effective filtration system to eliminate dust, pollen and other particulates.

Don’t underestimate the importance of correctly sizing the HVAC system. Correct sizing and installation ensures indoor comfort while at the same time saving energy and minimizing the cost of the system itself.

Use Manual J calculations with accurate data obtained by testing the tightness of the house, and by using high quality windows and insulation systems, and employing proper framing techniques.

Correct HVAC installation also requires that the distribution system be carefully sized and that all ducts in conditioned spaces are sealed tightly enough to prevent gasses from unwanted locations like garages and crawl spaces from entering the space.

Last, but not least, there must be simple controls that allow people to interact with the HVAC system to achieve the indoor environment they want.

A properly sized HVAC system, correctly installed, in a weather tight structure, will result in a comfortable, durable, healthy and energy efficient home. A home your customers will love to talk about!