GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter 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

How to vapour barrier and insulate?

Bill S | Posted in General Questions on

Hi,

I had originally posted this question on July 5th, 2013. I appreciate and say Thank-you to all of the feed back that has been forwarded.

Please bare with me as I am not savvy to all of the most recent info and building materials available now a days. I have done a pile of reading and studying and am ending up more confused the further I go.

Yes, code is important to bare in mind, but what is the right way and what works. I am no longer interested in building practices that don’t work but are forced down our throats any way. I like to try and do things right the first time and not look back.

Questions,

#1 What would be the best way to Air seal the common wall between the heated basement and sometimes unheated garage. I will be keeping the Garage/Workshop heated slightly to keep the tools from being damaged.

– Would having it sprayed with closed cell foam ,ceiling to floor, do the job of insulating and air sealing to create two separate entities.
– Would this meet code.

– Could I use closed cell rigid insulation between studs and joists and closed cell spray foam around the edges to insulate and create an air seal.

– Would this meet code.

– If I was to use Roxul insulation or glass bat insulation what would I do to air seal on the basement side of the wall, from the floor to the ceiling.

#2 The ceiling in the garage is heavily insulated with glass bats and Roxul bats but there is no vapor barrier any where. What should be done here.

#3 The walls of the garage are going to be insulated and Air barrier-ed, what is the best way to insulate and air seal these outside walls.

Thanks again for all and any information. W.S.

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.

Replies

  1. GBA Editor
    Martin Holladay | | #1

    Bill,
    Q. "What would be the best way to Air seal the common wall between the heated basement and sometimes unheated garage? Would having it sprayed with closed cell foam, ceiling to floor, do the job of insulating and air sealing to create two separate entities? Would this meet code?"

    A. You can use spray foam to air seal and insulate the wall if you want, but it is not the only way to do the work. Garage walls must meet local codes for fire safety; in all cases, you will want gypsum wallboard on both sides, and in some jurisdictions, one or both layers of drywall will need to be 5/8-inch thick. Check with your local building office to find out what is required in your area.

    Q. "Could I use closed cell rigid insulation between studs and joists and closed cell spray foam around the edges to insulate and create an air seal?"

    A. Yes, but this approach is fussy and time-consuming. In my opinion, cutting big pieces of rigid foam into narrow strips and installing the strips between studs is a waste of good foam. It makes more sense to install the rigid foam as a continuous layer on one side of the wall.

    Q. "Would this meet code?"

    A. Only if you used enough rigid foam to meet minimum R-value requirements, and only if the walls were finished on both sides with drywall.

    Q. "If I was to use Roxul insulation or glass batt insulation, what would I do to air seal on the basement side of the wall, from the floor to the ceiling?"

    A. You could use the airtight drywall approach or sprayable caulk. Click the links for more information on these topics.

    Q. "The ceiling in the garage is heavily insulated with glass batts and Roxul batts but there is no vapor barrier any where. What should be done here?"

    A. You don't mention your location or climate, so it's hard to answer your question. But most ceilings do not require a vapor barrier. Air sealing is much more important than controlling vapor diffusion. For more information, see Do I Need a Vapor Retarder? and Vapor Retarders and Vapor Barriers.

    Q. "The walls of the garage are going to be insulated and Air barrier-ed. What is the best way to insulate and air seal these outside walls?"

    A. You can choose from a wide variety of insulation materials. Almost any insulation will work well if it is installed conscientiously. Attention to air sealing is important, no matter what insulation you choose.

Log in or create an account to post an answer.

Community

Recent Questions and Replies

  • |
  • |
  • |
  • |