Residential Ventilation


Heating and cooling account for between 40-60% of energy used in U.S. residential buildings. This represents a large opportunity to save energy throughout U.S. buildings. One of the leading cause of energy waste from heating and cooling in both commercial and residential buildings is inadequate insulation.

The air within homes can become stale from moisture, odors, and pollutants that penetrate the building or are generated internally by human activity and off-gassing from building materials and furnishings. A steady supply of fresh outdoor air can increase indoor air quality and improve occupant comfort. Historically, residential buildings have not had specific requirements for ventilation because natural air leakage and natural ventilation was considered adequate. As envelope construction practices have improved and the envelopes of residential buildings become tighter, the need to ensure air quality through practices like mechanical ventilation has risen.


Mechanical ventilation systems circulate fresh air into the home to replace stale and/or moist air. For buildings that have mechanical ventilation systems installed, the IECC requires an automatic or gravity damper for any intake or exhaust protruding through the envelope. The goal is to reduce air leakage through the envelope when the ventilation system is not in operation. Health concerns make the circulation of air necessary for occupants. Mechanical ventilation system requirements achieve balance between occupant health and energy savings.

Any mechanical ventilation system will not reach its performance potential if components are poorly manufactured or installed improperly. Several factors contribute to poor performance of ventilation systems including long duct lengths and compression in flexible ducts, each resulting in a loss of ventilation rate and a significant increase in power and energy consumption by HVAC systems.


2015 IECC Section R403.6 Mechanical Ventilation (Mandatory)
The building shall be provided with ventilation that meets the requirements of the International Residential Code or International Mechanical Code, as applicable, or with other approved means of ventilation. Outdoor air intakes and exhaust shall have automatic or gravity dampers that close when the ventilation system is not operating.

Advanced Code Options

There are many new and innovative mechanical ventilation products available that can save energy, decrease utility bills, enhance thermal comfort, and improve indoor air quality. Examples include more stringent requirements for ventilation fans, pollution or moisture-based source-point ventilation, and whole-house ventilation systems; requirements for automatic controls or systems capable of being set remotely for continuous operation.

The following sections provide examples of code improvement language or methodologies along with technical examples of how to meet or exceed code.

Residential Policy Recommendations

More stringent requirements for ventilation fans, pollution or moisture-based source-point ventilation, and whole-house ventilation systems: Vermont Residential Building Energy Code Handbook, Fourth Edition

Technical Recommendations
When attempting to determine the best way to ventilate a home, it is important to ask these four questions:

  • How much outside air do you need?
  • How do you distribute it throughout the house?
  • How do you clean it?
  • Do you add or subtract moisture?

Code History

The 2009 IECC covered HVAC ventilation in Section 403.5. The 2003 IECC required automatic or gravity dampers and a readily accessible on/off switch. The 2006 and 2009 versions of the IECC included the former provision, but eliminated the latter. Their wording is otherwise identical.

Typical Problems

Standard issues/concerns that arise include:

  • Contractors or sub-contractors not accounting for mechanical ventilation in bid or final construction
  • Minimal guidance in the 2009 IECC