Can a house be too airtight?

Indoor Air Quality Facts

“Once upon a time, there was a house that was SO well-insulated that it was TOO airtight.” The famous first four words here are key when discussing indoor air quality. Modern building science tells us that times have changed, making this little scenario nothing more than a “back-in-the-day” fairy tale.

The true story? Your home simply cannot be too airtight.

Properly applied open cell spray foam between wall joists.

Spray polyurethane foam, known for its unbeatable contributions to comfort and energy efficiency (not to mention a host of other benefits), is increasingly becoming the insulation of choice. Its many “talents” hinge upon making homes more airtight than was once even thought possible – something that people used to worry might be bad news for air quality. However, most modern industry professionals agree that an airtight home is a total plus, as long as builders, HVAC contractors, insulation experts – and even homeowners themselves – work together, and understand that the various components of the home must work together too.  

  • Select a ventilation plan that complies with ASHRAE standards for indoor air quality.
    (Remember that new homes built with spray polyurethane foam insulation throughout typically need mechanical ventilation.)
  • Follow the EPA’s ENERGY STAR® standards for selection and sizing of HVAC systems using Manual J.
  • Choose sealed combustion or power-vented equipment for homes with spray polyurethane foam insulation. (That means no “naturally aspirating” or open-combustion furnaces, water heaters, or appliances.)
  • Perform a blower door air test to ascertain a home’s air quality (in regard to ASHRAE standards) and help assess ventilation effectiveness, both before and after installation of spray polyurethane foam insulation.

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When it comes to this last point, Sunlight Contractors always has you covered. Conducting  blower door air testing is just another example of our commitment to professional service, with all of your best interests at heart.


The professionals at Sunlight Contractors are dedicated to making your home airtight, while keeping it “air-safe.”

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