GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter X Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

Air quality issues from air sealing attic?

AtticAdventures | Posted in Energy Efficiency and Durability on

If I air seal the ceiling plane of a client’s attic using canned spray foam, caulk, rigid foam, etc., what is the chance I’ll cause an indoor air quality issue because the house no longer has sufficient ventilation?

Most of the homes I work with are at least 15 years old. I realize in an ideal world you would do before/after blower-door testing and all the combustion appliances would have dedicated air intakes but that just isn’t a financial possibility for my clients.

My gut feeling is that these homes are so leaky in other areas other than the attic plane that they still won’t be “tight” in any real sense after attic air sealing. Interested to hear if anyone else has any experience with this.

Thank You for your advice.

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


  1. stuccofirst | | #1

    You can't really judge what will happen, or what kind of improvement is made without measuring. i.e. blower door. Every house is different, with its own unique infiltration issues whether its 2 years old or 100 years old..

  2. GBA Editor
    Martin Holladay | | #2

    Your question is common, and it is hard to answer. If you are willing to perform a blower-door test, you can follow the advice of John Straube: When is a house tight enough to need ventilation?

    If the house won't be tested with a blower door, I think there is nothing wrong with using common sense. If the house doesn't exhibit any of these problems, you probably don't need any changes to the mechanical ventilation system (or lack of same):

    1. The house has odors that can't be blamed on bad housekeeping.

    2. The house has persistent mold problems on ceilings, walls, or window sills.

    3. The house has noticeable problems with window condensation.

    If any of these conditions exist, start by running the bathroom exhaust fan(s) for a longer period of time each day. If problems persist, it may be time for a more elaborate ventilation system.

    Remember, overventilation incurs an energy penalty.

  3. stuccofirst | | #3

    make sure CO detectors are installed and operating.

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |