See Table 3 in this document, the column labeled " 1" ccSPF + Spray Fiberglass", rows "4A Boston" and "4A Kansas City":Īnd that's at much higher fiber-R levels than you'd be looking at. Protecting the roof deck from interior side moisture drives only takes about an inch of closed cell foam. >"Is there a MINIMUM thickness required to prevent moisture issues?" I can post more photos if needed.īTW, in in SE Pennsylvania. after reading Martin’s numerous warnings…I’m second guessing this.ģ – leave it as its been for 100 years, pay the extra $20-50/month in heating/cooling and spend the time playing w/ my kid….Īny suggestions are appreciated.
#Exposed rafter ceiling iso#
concerns are pretty much as Martin stated above – smell and dust in our open living room as well as trapping moisture in the sheathing should the roof ever leak (thought I’m already taking on this risk on the other side of the house).Ģ – I was considering “cut and cobble” with 2″ of poly iso and spray around the edges, then adhere the same painted 1/8″ paneling on top. this was suggested by a spray foam contractor. trim down to the 2″ then tack up painted 1/8″ paneling and trim. The goal is to provide air sealing and some insulation in between 4.5 deep rafters, while keeping exposed rafters and a smooth finish in between.ġ – nail in 1×3/4 strips along the rafters spaced 1″ off the sheathing, then have 2″ closed cell sprayed in. So now – we are mid construction, the house is getting reroofed next week, the new work is getting all interior closed cell spray foam, but we did not address this part of the house. Maybe I could have done it cheaper if it wasn’t part of a general contracted job – but it couldn’t happen that way. Adding 4″ of XPS was going to be nearly $30k more than traditional insulation for the new addition due all the trim work and window pans required to tie it together. A year into finding a contractor for another addition and reroof – I pulled the plug on the exterior rigid foam. We also have two shed dormers at the front and back.īased on my reading here this would be a perfect application for exterior rigid foam. Between the rafters are (what looks like) tin foil then 1/2 homasote board. Its basically one big 24×24 room with a high (17ft) hip roof “cathedral” ceiling with exposed 2×5 (go figure) rafters (there is also a more traditionally built 1930s addition attached). I have a house that started as a summer cabin around 1900. This would not be a good solution in a cold climate, where you would have to insulate against conductive heat losses from inside the building.I’m not sure if this has been asked before – I searched and couldn’t find it. The space should be ventilated with continuous soffit and ridge vents. The roof would then have about the same insulating value as R-11 fiberglass against downward heat flow. Use either two layers of reflective foil insulation installed back to back, or one layer of a "double-polished" reflective material, which is shiny on both surfaces.
This would prevent the building from absorbing a significant amount of heat, providing the radiant barrier has at least a 1/2-inch air space on either side.
#Exposed rafter ceiling install#
In warm climates, a second possibility is to install a new roof deck on 2x2 sleepers over the existing sheathing, with a radiant barrier between the old and new roof decks. The first method is to install a urethane foam insulation board and a new plywood deck over the existing sheathing (see illustration). There are two ways to handle the insulation problem. Fiber-cement shingles weigh just a little more than architectural-grade asphalt shingles (approximately 400 pounds per square when installed).
These are becoming more widely available and seem to provide a long-lasting roof without adding much weight. If the framing won’t support the weight of concrete tile, my choice of roofing in a hot climate would be fiber-cement shingles.
What is the best roofing and insulation to use on a 20-year-old house with exposed rafter cathedral ceilings? The framing doesn’t seem strong enough for tile, which is common here in the Southwest, and the roof needs substantial insulation to shield against an extremely hot summer climate.Ī.
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