help insulating/ventilating 70’s gambrel
Here is my issue, I have a poorly insulated Gambrel build in the early 70’s. I just finished the roof and trying to eliminate drafts and insulate the crawl space. I have air movement between floors and my crawl spaces are cold and unconditioned. The way my particular Gambrel here on Cape Cod was built, the actual attic rafters overlap at the “kneewall” the crawl space rafters requiring the use of a 1×8 fascia trim to adjoin the upper and lower roofs. The roof has not had any moisture/ventiliation issues in the past. My questions are this: Is it best to keep my storage eaves unconditioned to allow air to travel to the attic? I planned on filling the floor of the crawl space with cellulose over the existing R-13, cutting 2″ foam board and fitting between floor joists at the knee wall and the soffit, thus stopping air flow between floors. And lastly applying 2″ foam over the back of the knee wall which already has R-13 batts and installing foam chutes at the top plate where eaves and the attic join to promote air flow to the upper section of the roof. Will I notice a difference? My plan sounds like it would work but, I can’t imagine cutting all the 2″ foam around the rafters…. Any Ideas ? ? ? ?
Edited 9/17/2008 6:49 pm ET by Bioengineer
Replies
Thanks for all the input....
So what do you want? Would you rather have a fast answer from someone who doesn't really know or wait until someone who does comes along?
I have a story and half house finished in 1972. I just completed almost exactly what you are proposing. I used 2" Thermax mostly because of the fire rating and the biggest issue was just getting in there and doing it. No room to maneuver. I wanted the biggest bang for the buck. Some differences was any ceiling light fixture I put a metal Kitchen bowl bought cheaply at Walmart over . I laid a little foam then placed the bowl in it. This air-sealed the fixture and keep the insulation off the electric box because older wiring won't take the heat build up as well as new wiring. The cellulose will keep the box warmer. I foamed the outside of the kneewall where I saw the existing fiberglass was missing. This was around wall outlets and very small stud spaces. I caulked the bottom of the kneewall to keep air from moving under it in or out. Additionally I discovered the soffet vents were letting air in the unconditioned space and the insulated rafters above were not allowing it to escape. I bought some 1-1/4" carlon pipe and slid it on top of the upper roof insulation which gave the heated air some place to go in the summer. Finally I installed Dormer Doors from http://www.access-doors.net and made a second door for each unit on the outside of the knee wall and glued 2" insulation to it and weatherstriped it also. Some thought are run additional spare electric and cable wiring before you install the cellulose. Once done you won't be able to get back into the space. Do all the work when it is cool outside otherwise the heat is intense. Works best with help. One on the inside and one bringing material to the first as you go. When I finished it made a big difference on my cooling load. Have not had a heating season yet but expect it to work well. It was not easy but I think it was worth it. Good Luck