A. You need to only use an installation method that your insulation contractor is knowledgeable about. Below within the Northeast, many contractors would likely fill your rafter bays utilizing the dense-pack strategy right after your new roof sheathing was put in.
Okay, I had been figuring that the entire on the rigid foam + cellulose had to be a certain R-benefit together and were thinking about applying much less rigid foam. I have been looking at about diverse forms of cellulose. Since I am installing from over would a thing like stabilized cellulose do the job because it has a bit drinking water added?
The danger is inside dampness will migrate to your chilly sheathing, leading to condensation or moisture accumulation.
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During the absence of an airtight ceiling, roof air flow can perform extra hurt than good, given that air motion in rafter bays can motivate indoor air to leak by ceiling cracks.
Recall: Because your roof assembly is dry, does not imply it is nicely insulated. Your assembly might have huge air leaks that work as thermal bypasses. (Or not. It really is challenging to convey to with out a site pay a visit to.)
It is a code violation to install an air-permeable insulation like fiberglass batts amongst unvented rafters. It's also a bad thought, mainly because humidity can accumulate in your roof sheathing if you are attempting this technique, and you will end up having sheathing rot.
I have created log residences during the Yukon Territory in northern Canada for 30 many years. Most log buildings have cathedral ceilings. Many of the roofs We have now constructed are as follows (from The underside up): log purloins, nominal two" (2x6) t&g decking, 6mil poly, one 1/2" extruded polystyrene foam, 2x10 rafters on 24" facilities, seven" fiberglass, 2x4 strapping, 7/16 OSB, underlayment (fifteen lb paper, 30lb felt, or now we'd even use ice and h2o protect). There might be about an inch of air Place underneath the strapping for both equally why not find out more vertical and horizontal air move. All roofs are vented with strip vents within the eaves and vents in the soffit (2x6 t&g) at the peak at both of those finishes. I would disagree that venting is not wanted in case you stop the airflow on The nice and cozy side, for two motives. Initial it truly is very difficult to halt all airflow, Specially with regular standard methods (ie chimney and plumbing vent penetrations from the roof) We have several methods made through the years to seal the vb for the eaves and gables, but there are still nail penetrations from the vb. General I feel we had incredibly tight seals but just one could in no way say airtight.
I'm unsure in the event you have an interest in the making science response or possibly a code respond to. From a code point of view, this can be a roof that needs to be insulated to R-49.
Not surprisingly, you can expect to continue to have thermal bridging from the rafters. But you won't have any humidity complications.
I've a mansard roof with steep sides with gables, and a nearly flat major having a check my reference rubber roof. There aren't any vents, it has not been insulated ahead of I began engaged on it and have 2 thoughts:
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I am sorry for being the bearer of negative news, however the sections of roof which can be insulated with six inches of fiberglass and interior polyethylene weren't insulated appropriately. In All those sections, the roof sheathing is prone to dampness accumulation and rot.
I am a homeowner in Seattle. Have got a newly-framed, vented cathedral ceiling to insulate. Straight bays, 2x12, 24" o/c. The current program is to utilize batts of some sort inside the bays, consider treatment to air seal the inside floor, prevent penetrations, air seal the vent channel way too (bays entirely sealed), double prime The within area for vapor resistance. I've a couple questions on baffling the vent channel: one. Several of the constructing experts I'm dealing with come to feel the jury continues to be out on baffles and therefore are recommending leaving the batts open towards the channel other than near the vents, assuming the one-2" air channel is often maintained.