Should I use rigid foam boards to insulate the garage roof? There will be a gap between the roof decking and the rigid foam boards to allow for proper airflow.
Should spray foam be used on the underside of the roof decking in the garage and also the family room? The attic space will not be used for any purpose.
Should I use 6 mil plastic as a vapor barrier under the rafters before sheet rocking the garage ceiling and having fiberglass insulation R-49 blown in on top of the sheetrock? This garage will become the mini-split heated & cooled master bedroom, bathroom and laundry room in the next 6 months. A new garage & shop will be built to replace this current garage.
I just bought a 2-story 3,000 sq ft home over a finished basement in the Black Hills of South Dakota, USA. It has not been updated since it was built.
The 1.75 car garage (2-car with a mud room of the family room) has sheetrock on the walls but it is unknown if there is insulation in those walls.
The family room and garage have the same roof line and there is fiberboard nailed to the trusses to separate the garage and family room roof/attic areas. The family room has one single layer of batt insulation with plastic sheeting between the sheetrock ceiling and the batt insulation. The garage ceiling was never insulated or sheetrocked.
I am going to have the house reinsulated. Both companies that are providing quotes want to install soffit vent barriers and then blow in fiberglass insulation to get up to R49. This sounds good to me.
This 53 year old house currently has a plastic vapor barrier behind/above the sheetrock. This is based upon us seeing it and cutting it when removing walls and adding LED lights to the family room ceiling. I believed the garage ceiling would also require plastic sheeting prior to sheet rocking the ceiling.
One insulation contractor did not mention it for the garage ceiling; the other contractor said no because of potential moisture issues when I mentioned a 6 mil plastic vapor barrier.
To reasonable the questions:
- Use rigid boards in the garage/future master bedroom, bath, and laundry room?
- use spray foam on the underside of the roof decking above both the garage/future master suite and family room? The attic space will not be used for any purpose.
- use 6 mil plastic under the R49 fiberglass blow in insulation and on top of the sheetrock?
TIA
