I live in Minnesota where the temperature ranges from -20F to +90F for an average year. I’ve seen as low as -40F on rare cases and as high as 100F also in rare cases. I would like to completely finish my attached garage complete with a furnace and an air-conditioner.
The garage currently has sheet rock. When I stuck a sheet rock knife into the wall, I was able to pull out some insulation on the knife bevels, so I know it is insulated. I tested all the walls in this fashion. I did NOT however pull out or hear any plastic vapor barrier.
I plan to keep the garage at a minimum of 45F over the winters, while heating it to 70F when entertaining (maybe once or twice per month). The air conditioner will run once or twice per month in the summer only when entertaining.
Question 1: Should I remove all sheet rock to put in vapor barrier? Why would the garage have been built finished without it?
Question 2: The ceiling is also sheet-rocked and there is no insulation above it. Should I:
a) Run vapor barrier over each truss, stapling it to the sides and tops, so that it can run along the sheet rock that makes up the ceiling, and then put insulation over this?
b) Put insulation down between the trusses and then vapor barrier over the top?
c) Something else?
You would have to do a little research to find out if it’s what you need but they do make vapor barrier paint. I have only seen it used in bathrooms but you may find it could work for you.
You need to be super careful with vapor barriers–locate it in the wrong spot and you will have condensation where you don’t want it. I would suggest you NOT do the vapor barrier paint in general but depending upon the winter conditions where you live it might be applicable. There is no one size fits all solution since the climate varies so much in this country. I am not familiar with Minnesota climate but I know I wouldn’t use it here in the NW.
Call the local development office and talk to someone there. They will know how the garage should have been built originally by the year of construction and will tell you what you need now. You will probably have to get a permit if you are installing a furnace anyway.
Kraft faced fiberglass batt does not qualify as sufficient vapour barrier in my municipality (Calgary). When we insulate an unheated garage here we still install vapour barrier.
If he heats in the winter & air conditions in the summer which is the warm side? In winter the interior’s the warm side and in summer the exterior’s the warm side.
in a predominantly heating environment (Minnesota is that) the interior is the warm side. the house is closed with less air exchange, trapping moisture, for about four months.
in the summer the house would likely be ventilated for much of the time. being closed for air conditioning might go for days or a week periods.