I hope someone can advise me regarding the following insulation-related issues:
I am purchasing a home in central New Hampshire. The home has a heated addition and, adjacent to that, a 2-car garage. There is also a heated living space above the garage. The heated addition + attached garage with heated living space above were added on to the original house about 15 years ago.
The previous owner did not install a firewall on the interior garage walls and ceiling – a violation of code. Town code requires 5/8” firecore sheetrock on the ceiling and all 4 garage walls (all 4 walls because all 4 walls support the living area above the garage).
The previous owner did, however, install yellow fiberglass batts between the 2×4 wall studs on the wall adjacent to the new heated addition and between the rafters on the garage ceiling to insulate the floor of the living space above the garage. The 3 outside walls of the garage (the back wall, side wall and wall where the garage doors are) are not insulated.
Before the firecore sheetrock is installed I would like to insulate the garage walls in case I decide to heat the garage later on. I also might consider adding additional insulation to the ceiling of the garage to better insulate the living space above the garage.
My questions relate to the proper way (e.g. what type(s) of insulation, need for vapor barriers or not, insulation options, etc) to insulate all walls, and if I can/should add additional insulation to both the wall and ceiling that already have fiberglass batts installed between the 2×4 wall studs and rafters. Specifically, I have the following questions I hope someone can help me with:
1. Is it ok to leave the yellow fiberglass batts currently installed between the studs of the wall adjacent to the house addition and ceiling rafters as is? I don’t know if there is a vapor barrier on the back side (unexposed) of the fiberglass insulation or if there should be one.
2. For the wall and ceiling that already have fiberglass batts installed, would it make sense to add additional insulation (for example, some sort of rigid, non-compressible foam insulation board) over the studs and fiberglass batts and then put the firecore sheetrock over this foam board? If so, should the additional insulation have a vapor barrier or not?
3. For the 3 walls exterior garage walls that are currently uninsulated, what is the correct way to insulate them prior to installing the firecore sheetrock, and what are the appropriate types / features of the insulation? For example, should I use insulation with a vapor barrier, etc?
I appreciate any advice regarding these questions.
NH Homeowner
Replies
Good questions
Although you broke it down into 3 questions, you are asking essentially the same general questions in each. This won't address all of the finer details, and it's not trying to, but will give you an idea of some things to investigate.
First, if the insulation has a vapor barrier, it should face the "warm in winter" side of the enclosure. In NH, that means it should face the conditioned living space. Second, I wouldn't try to compress the existing fiberglass in order to add anything into the bays. A better approach would be to pull out the batts and meticulously seal any gaps, seams, holes, electrical boxes, plumbing penetrations, etc with spray foam, then neatly reinstall the batts. You can add rigid insulation on the interior side of the wall, over the studs or ceiling joists, but this may require the addition of wood furring strips over the foam so that you can tie the drywall back to the structure.
For more on these topics, I highly suggest you visit our sister site, http://www.greenbuildingadvisor.com
Insulation
I do this all the time down here on the Seacoast.
Check my website or contact me if you need more advise
jim
Maintenacemen.com