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

Garage ventilation

peter2022 | Posted in General Questions on

I have an attached gable-roof garage that is uninsulated.  I’m retrofitting the house’s roof with R-20 exterior foam insulation, that will extend over the garage as well.  The only benefit I expect for the garage is to reduce peak summer temperatures.

Currently the garage has 3 passive roof vents, no soffit or gable vents.

My 1st thought is to replace the passive vents with a single active (fan) vent.

– Is there any downside to this?  Do I also need passive roof ventilation? Soffit openings?

– Also, the roof sheathing over the house will be taped as the primary air barrier (below the foam), any downside to continuing that over the garage?

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. walta100 | | #1

    I do not care for the powered vent fans in attic. Generally, they tend to depressurize the attic and pull conditioned air from the home putting more of a load on the AC unit.

    If you have no ceiling in the garage and you only wanted to operate the fan when the overhead door was open seems pretty harmless.

    The only reason we vent attic is to prevent warm moist air that escapes into the attic from building up and condensing in the attic. The amount of venting we do has almost no affect on summer attic temps.


    1. peter2022 | | #2

      Thanks, I was not thinking about how the lack of the humidity problem in the garage changes the ventilation requirements.

      Our garage has no ceiling but it also does not share any attic space with the house so I'm not too concerned about depressurization.

      I'll have to think a bit more on whether I want to have an active or passive strategy - I suppose I can just put in an exhaust vent cap designed for fans and then decide later whether I want to leave it passive or hook up a fan.

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |