All the labor that goes into producing tighter houses results in remarkable energy savings and greater comfort. But cooking odors, moisture, and chemical toxins can’t disperse as easily in a house with a tight envelope as in a leaky house. Opening a few windows may yield too much or too little ventilation, with unfortunate effects on comfort in either case. Even in houses where furnishings and building materials have been carefully selected to reduce indoor air pollutants, some arrangement of mechanical ventilation is a prerequisite for healthy inhabitants and a healthy building.
There are two fundamental strategies to produce mechanical ventilation: spot ventilation, which eliminates pollutants and moisture at their source, and whole-house ventilation.
Classic spot ventilation strategies incorporate the use of bathroom exhaust fans and an exhaust fan over the kitchen range. Exhaust fans are available in a assortment of styles, sizes, and price ranges. Control options range from simple wall switches to advanced timers, humidistats, or occupancy sensors.
Whole-house mechanical ventilation systems are created to remove stale air from or provide fresh air to the building as a whole. These systems are more complex and more pricey than spot ventilation systems, but also more efficient.
Use a Variable Speed Furnace Fan
Some ventilation systems utilize the furnace fan to distribute air throughout the house. In these systems, the fan speed used for heating and cooling is more than likely too high in a ventilation-only mode. A variable-speed or two-speed fan is more effective, using less energy for ventilation than for heating and cooling.
Air Sealing Makes a House Healthier
In designing any ventilation system, a few rules of thumb are applicable:
The domicile should be air-sealed carefully, especially when it comes to crawl spaces, basements, garages and other areas where toxins and pollutants are familiar.
Building furnishings and materials that emit the least amounts of pollutants should be a first alternative.
The most effective ducts are straight, smooth, sized correctly, and sealed tightly. Corrugated ducts have considerable resistance to airflow, and elbows and long runs of duct also diminish effectiveness. Duct joints should be sealed with mastic. Ventilation ducts that pass through out unconditioned spaces should be insulated.
Exhaust ducts should always be ventilated to the outside every time, not into attics, basements, or crawl spaces.
Don’t Forget About Radon
Radon, a naturally occurring radioactive gas, is the second leading cause of lung cancer in the U.S., accounting for between 15,000 and 22,000 deaths a year, according to the National Cancer Institute. Radon can migrate through the soil and into basements, or access a building via well water. Some sections of the country are at a far more considerable risk than others, but all families should have their houses tested for it.
Especially in high-risk areas, a vent system created to pick up radon from beneath the basement slab should be installed during the construction of your home. If tests later indicate radon levels are too high, it’s actually quite easy to install a fan and get rid of the the gas before it can do any harm. Installing a radon mitigation system after construction is finished is that much more of a painstaking process.