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Step 2A Discussion About Insulation and Vapor Barriers
To borrow from Wikipedia, R-value is a measure of thermal resistance used in the building and construction industry. The bigger the number, the better the building insulation's effectiveness. Given that I was building a passive-cooling system, I needed to maximize my R-value. Also, because I was going to humidify the closet, I needed a vapor barrier to prevent moisture from escaping.
I found an effective solution to both of these issues. Reflectix manufactures a reflective insulation that not only acts as a vapor barrier, it also increases the R-value a little bit.
For the main insulation, I decided on standard fiberglass insulation. I picked up some Owens Corning kraft-faced wall insulation, which has an R-value of R-13. While there are other fiberglass insulations with a higher R-value, this one fits inside a standard wall made with 2x4s.
Kraft-faced insulation is a little more expensive, but a big plus is that it adds a vapor barrier to the cool side of the insulation, while the Reflectix serves as the vapor barrier for the warm side.
Since I couldn't tear out the existing walls (wife's requirement), my plan was to leave the existing walls in place, build new walls, floor, and ceiling using the Reflectix barrier and the Owens Corning fiberglass as insulation inside the new drywall. For the doors, my plan was to apply two layers of 2" thick reflective rigid insulation foam board to the existing doors.
So, I figured my R-values would be:
Floor = existing concrete, existing hardwood, one layer of fiberglass insulation, 3/4" plywood = R-value ~ R-20
Walls = existing wall, Reflectix barrier, one layer of fiberglass insulation, 1/2" drywall = R-value ~ R-25
Ceiling = existing ceiling, Reflectix barrier, two layers of fiberglass insulation, 1/2" drywall = R-value ~ R-38
Doors = existing door, two layers of insulation board = R-value ~ R-26
Of course, I'm writing this website after the fact. The one thing I would definitely do differently is I would have blown in insulation into the existing walls and ceiling before building my new walls. This would have easily increased my R-Value by at least another R-10. Apparently, at Lowe's, if you buy the blow-in insulation, they'll loan you the blower for free. Lesson learned.
On a side note, that Reflectix material is great. I bought a second roll and mounted it on the inside of my garage door. We haven't hit the really hot days yet, but I have noticed a significant reduction in the garage's ambient temperature. I may do up the attic with this stuff.
I found an effective solution to both of these issues. Reflectix manufactures a reflective insulation that not only acts as a vapor barrier, it also increases the R-value a little bit.
For the main insulation, I decided on standard fiberglass insulation. I picked up some Owens Corning kraft-faced wall insulation, which has an R-value of R-13. While there are other fiberglass insulations with a higher R-value, this one fits inside a standard wall made with 2x4s.
Kraft-faced insulation is a little more expensive, but a big plus is that it adds a vapor barrier to the cool side of the insulation, while the Reflectix serves as the vapor barrier for the warm side.
Since I couldn't tear out the existing walls (wife's requirement), my plan was to leave the existing walls in place, build new walls, floor, and ceiling using the Reflectix barrier and the Owens Corning fiberglass as insulation inside the new drywall. For the doors, my plan was to apply two layers of 2" thick reflective rigid insulation foam board to the existing doors.
So, I figured my R-values would be:
Floor = existing concrete, existing hardwood, one layer of fiberglass insulation, 3/4" plywood = R-value ~ R-20
Walls = existing wall, Reflectix barrier, one layer of fiberglass insulation, 1/2" drywall = R-value ~ R-25
Ceiling = existing ceiling, Reflectix barrier, two layers of fiberglass insulation, 1/2" drywall = R-value ~ R-38
Doors = existing door, two layers of insulation board = R-value ~ R-26
Of course, I'm writing this website after the fact. The one thing I would definitely do differently is I would have blown in insulation into the existing walls and ceiling before building my new walls. This would have easily increased my R-Value by at least another R-10. Apparently, at Lowe's, if you buy the blow-in insulation, they'll loan you the blower for free. Lesson learned.
On a side note, that Reflectix material is great. I bought a second roll and mounted it on the inside of my garage door. We haven't hit the really hot days yet, but I have noticed a significant reduction in the garage's ambient temperature. I may do up the attic with this stuff.
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