Indoor air contains up to 100 times the pollutants of outdoor air. In a state like Minnesota, where people can spend large amounts of time indoors during the winter, clean indoor air is vital to good health. If your house is stuffy, smelly, or very humid, it may be the case that your house is not adequately ventilated.
Proper ventilation removes contaminated air that can cause health issues –smoke from cooking, moisture from bathing, combustion products from heating systems, and volatile organic compounds from household solvents. This initial air removal is necessary –and in fact, some ventilation is required by statute in living spaces –but it is just the first step. Ventilation is a two-way street. Air pulled out of the home must be replaced somehow. In the past, this was accomplished with the air that leaked into the building around windows, doors, or foundation cracks. In a well-sealed home, however, there are very few of these leaks.
Balancing air flow to prevent positive or negative air pressure inside the home is the idea behind thoughtful ventilation.
Pulling contaminated air out from the source
Point source ventilation areas are located near the source of contaminated air, such as in the kitchen, bathroom, or workshop. These are exhaust-only systems –pulling air from inside the house with a fan and exhausting it to the outside through ducts.
Building code requires that bathrooms have either an operable window or a fan to remove odor and excess moisture. A bathroom fan is often quicker and more effective than opening a window –especially during heating or cooling season. In order to minimize moisture buildup and mold, it is essential that bathroom fans be installed properly, using short, insulated ducts with no bends or kinks. Additionally, fans must be air-sealed at the ceiling and insulated to prevent heat loss into the attic. Ducts must also be sealed at all joints and connections, all the way through to the exit point at the roof or wall. Look for ENERGY STAR rated fans for quieter, more energy-efficient options.
Most kitchens have hood fans over the stove top or range. Unfortunately, many are not connected to ducts that lead to the exterior, and are merely recirculating the air through the fan filter. Although this may collect some of the larger particles of grease, these installations will do little to control smoke, odor, or the polluting by-products of combustion. The same requirements for proper installation apply to kitchen fans are to bathroom fans, and ENERGY STAR products will perform best.
Make-up air from point-source loss usually comes in through an insulated duct that enters the house (often through the basement). When properly installed, this duct will only allow the entry of air when needed.
Balancing overall air flow in the home with air exchangers
Air exchangers do exactly what their name implies: they exchange stale indoor air with fresh air from the outside. Although the energy savings available through using an air exchanger are minimal, the benefits are felt in other important ways.