Today's homebuyers demand tightly sealed and well-insulated homes for lower energy bills and increased comfort. Unfortunately, stale air can build up in these homes, causing indoor air quality problems. This has created the need for active, whole-house ventilation systems that bring in controlled quantities of fresh air.

A fresh approach

Whole-house ventilation systems provide controlled, uniform ventilation by using one or more fans and duct systems to exhaust stale air and supply fresh air to the entire house.

There are several types of systems:

• Exhaust-only removes stale indoor air; makeup air infiltrates through leaks and passive vents.
• Supply-only draws in outside air with a fan; inside air leaks out through holes, ducts and vents.
• Balanced brings in fresh outside air and exhausts stale air in equal amounts using multiple fans.

Balanced systems are the most expensive. Operating costs can be higher because heating and cooling of makeup air is required for certain seasons and climates.

Advanced systems come with smart controls, which provide ventilation only when required. ENERGY STAR® multispeed fans with low sound levels also are available. The efficiency of balanced systems can be improved with energy recovery ventilators.

Advantages and disadvantages

Whole-house ventilation systems come with many benefits. They improve the indoor environment through better air flow, and help control moisture and wintertime condensation. For builders, they can reduce callbacks due to moisture problems, odors or air quality complaints.

There are extra costs involved, however, and whole-house ventilation isn't right for every situation. Consider the following before switching to this building technology for your projects:

• Installation costs range from hundreds to thousands of dollars. In addition, the HVAC system will cost more to operate than a home without a supplemental ventilation unit, unless you integrate an energy recovery ventilator.
• Be prepared to explain how the system works, its advantages and how it will benefit homeowners.
• Exhaust systems are best for colder climates. In hot, humid areas, these systems may bring moisture into the home through makeup air. An add-on dehumidification unit may be necessary, driving up costs.
• Work with a qualified HVAC contractor who has experience in installing these types of systems.
• Proper sizing is important, particularly in small, tightly constructed homes that use vented fuel-burning appliances. An oversized ventilation system can cause backdrafting in fuel-burning appliances. Consult the federal and local building codes for relevant requirements.

Best practices

Use these guidelines when implementing whole-house ventilation systems:

• Ensure the home is tightly constructed.
• Select a system design appropriate for the home and the climate.
• Consider sizing and combustion air requirements for fuel burning appliances.
• Make sure the wiring system is appropriate for the system's electrical load.
• Consider ventilation system control issues.
• Provide the homebuyer with information on the operation and maintenance of the system.

ANSI/ASHRAE Standard 62.2 is the recognized residential standard for ventilation system design and acceptable indoor air quality.