xd2005
Member
- Messages
- 36
- Reaction score
- 0
- Points
- 6
I just received my permit from the city on a partial garage conversion to living space. The garage is not ideal for this type of thing, but I've been working through the various issues and had everything nailed down (thus the permit).
I have 2x4 rafters, which I will be sistering with 2x6 rafters to increase the support, as well as adding 2x6 collar ties. My main issue has been height, as the walls are only about 80" tall, so clearance has been a significant issue I've had to deal with. Because of the height issue, I have limited insulation space for about 1/2 of the roof space, until it gets to the collar tie level and opens up to allow more room for insulation.
Before submitting my application for the permit, I talked with the city and they told me that I should be able to fit foam insulation (sheathing) into the space (5.5") and be able to meet R-38 requirements. When I got my permit today, it was noted to use "Foam or Foil R-38." It was also stamped (on another page) "min 1" of air space; extend baffle 6" above batt insulation; 12" above blown WSEC 502.1.4.5."
Considering I have 2x6 rafters and need 1" ventilation space between the insulation and roof, I basically need to find a way to insulate 4.5" of space with R-38. Is this even remotely possible? When I was talking with the person from the city before submitting the application, he had indicated to use the foam because he said it had like r-8 or r-9 values per inch. In actuality, from what I can tell it's more like r-6 per inch (I have seen 0.5" with r-3.2, which at 4.5" would get me to a whopping 28.8 value, not really even close to R-38. So my questions are:
A.) Am I completely missing something with my calculations?
B.) If not, is there an insulation that would allow me to get an R-38 value utilizing 2x6s for rafters?
C.) Related, but different issue. Are soffits a requirement? Currently the garage has no ventilation at the eave level. I have 4 roof vents (2 will be above the "converted" side) and I had planned to put in a gable vent, but hadn't really thought of vents at the eaves.
Thanks.
Brian
Below is a ghetto image of what I am talking about:
I have 2x4 rafters, which I will be sistering with 2x6 rafters to increase the support, as well as adding 2x6 collar ties. My main issue has been height, as the walls are only about 80" tall, so clearance has been a significant issue I've had to deal with. Because of the height issue, I have limited insulation space for about 1/2 of the roof space, until it gets to the collar tie level and opens up to allow more room for insulation.
Before submitting my application for the permit, I talked with the city and they told me that I should be able to fit foam insulation (sheathing) into the space (5.5") and be able to meet R-38 requirements. When I got my permit today, it was noted to use "Foam or Foil R-38." It was also stamped (on another page) "min 1" of air space; extend baffle 6" above batt insulation; 12" above blown WSEC 502.1.4.5."
Considering I have 2x6 rafters and need 1" ventilation space between the insulation and roof, I basically need to find a way to insulate 4.5" of space with R-38. Is this even remotely possible? When I was talking with the person from the city before submitting the application, he had indicated to use the foam because he said it had like r-8 or r-9 values per inch. In actuality, from what I can tell it's more like r-6 per inch (I have seen 0.5" with r-3.2, which at 4.5" would get me to a whopping 28.8 value, not really even close to R-38. So my questions are:
A.) Am I completely missing something with my calculations?
B.) If not, is there an insulation that would allow me to get an R-38 value utilizing 2x6s for rafters?
C.) Related, but different issue. Are soffits a requirement? Currently the garage has no ventilation at the eave level. I have 4 roof vents (2 will be above the "converted" side) and I had planned to put in a gable vent, but hadn't really thought of vents at the eaves.
Thanks.
Brian
Below is a ghetto image of what I am talking about:
Last edited: