Whole House Ventilation

Purpose of Whole House Ventilation

Many people have heard the saying “a house has to breathe” and become very nervous when recommended to seal the house up tighter.  That saying is only partially true.  Fresh air must be brought into houses for two primary reasons:


  1. To provide air for the people in the house to breath
  2. To remove odors, excess moisture especially near bathrooms and kitchens, and to remove air pollutants given off by products like hard wood floors, carpets, and furniture

So, in reality, as long as enough fresh air is brought into the house to satisfy those two requirements, a house can be made tighter.  There are two main methods for ventilating a house:

Natural Ventilation

All homes naturally bring fresh outside air into the house unintentionally through air leaks in the exterior shell of the home. For most homes built before 2000 this is the only way fresh air is brought in. Air is driven through these gaps and cracks by wind and by the natural flow of hot air rising through the house.  The problem with this type of ventilation is that it is uncontrolled, on very windy days or very cold days too much air flows through the house that has to be heated or cooled depending on the season. On very calm temperate days very little air moves through the house.

Mechanical Ventilation

Fresh air can also be brought in to the house through intake or exhaust fans.  Intake fans bring air directly into the house from a vent on the outside of the house and this air is typically distributed in one location or through the HVAC duct system.  An exhaust system pushes air out of the house which forces air to flow through the gaps an cracks in the exterior shell of the house.  Either system can be set to a specific ventilation rate to ensure proper amounts of ventilation for the home.


Proper Amount of Ventilation


Ventilation at a specific rate determined by the size of the home and the number of occupants.  A mechanical ventilation system is required if a house is measured below a threshold based on the size of the home.  During every Home Energy Audit, we determine if your home is above or below the threshold and if the recommended air sealing work will push it below the threshold.  We can help design the ventilation system for your home based on the results of this test, and typically the most cost effective system is an exhaust system using a bathroom exhaust fan running continuously at a low speed or intermittently at a high speed.


An Atlas Energy Auditor can determine if your home needs a whole house ventilation system and which system is best to meet your comfort and energy efficiency goals.