I will be installing a steel roof on an existing building with a fairly low pitch (4 or 5 in 12) The roof is about 32 square. The interior of the building has a beautiful existing cedar T & G cathedral ceiling (17′) that I don’t want to cover. As far as I can tell, the existing roof deck has maybe 3 ” between it and the top of the cedar ceiling.
I will be removing the two layers of asphalt shingles and insulating from the top, if it’s worth it. I plan on using steel roofing that requires installation clips with as few exposed fasteners as possible. (Haven’t done steel yet.)
What is the best way to go about adding some insulation to this ceiling? If I add sleepers to the existing deck, I would probably run them parallel to the eave with rigid foam between them. How much would you put in there? 1 1/2 or 3 1/2? that’s alot of foam. 30# felt on top of existing roof deck or on top of sleepers? Is it necessary to put decking on top of sleepers? Not worth it at all?
Now here’s the real skinny……. It’s going to be rental property (duplex) when finished with all utilities seperated. I want to avoid my tenants having a $300/month heating bill for the hot water baseboard heat. I live in SW Michigan. Thanks in advance. Any input would be appreciated.
Jim
I don’t have a cute saying to put here. I’m new to this.
Replies
My suggestion would be to carefully mark out all rafter/truss tops so you can hit them with screws, then cover the whole thing (no sleepers) with 2" foam, cover that with 7/16 OSB screwed down to the roof framing you marked out earlier. I'd suggest either a double layer of 30# felt over the OSB.
Next: the cold roof. Run 1x2 laying flat from ridge to eave on 16" centers, then put 1x4 skip sheeting cross ways (perpendicular) to that. Fasten your metal to the 1x4's. The space created by the grid of 1x will allow for ventilation above the new insulation.
Make sure your inspector will accept it!
I've done it this way twice: once on new, once on a re-do. Yes, it's a lot of material and a lot of work.
Got the idea from a FHB article a long time ago. (1981?)