The longer which you hold out to setup rigid foam over your roof sheathing following your rafter bays are stuffed with fluffy insulation, the increased the danger that your roof sheathing will accumulate moisture. A few many years need to be no issue, but I would not stretch the workout Considerably farther than that.
It seems like you posted your inquiries on two various webpages. I have furnished an answer on the other webpage where you posted. Here is the website link to my solution:
Perfectly the roof is going on with the 1st layer of insulation (on-best the purlins, beneath the roof sheeting). There seems to get enough Place still left inside the 4" purlin cavity for the second layer of R11 being mounted with none modification.
This is the typical response for individuals who ought to adjust to most setting up codes (the answer comes from an write-up by Mike Guertin):
Hi Absolutely everyone. I see I'm slightly late to the get together on this thread but I hope someone can continue to assist me. From my issue line it is possible to see I've quite your house. I'm the home operator and frustrated with my leaky roof. I are in WI and my roof has asphalt shingles.
Problem just like Eric, earlier mentioned. If shut cell foam is sprayed or "cobbled" from xps, do It's important to fill the entire space, or only to thickness for preferred R value?
If at all possible, incorporate a ventilation channel higher than the highest of your insulation layer. The air flow channel will supply low-cost insurance policy in opposition to moisture Make-up, and will reduced the prospect of ice damming.
(d) There may be visit homepage adequate air leakage within the "soffit" and ridge to supply air move that acts just how a air flow gap ordinarily would.
The roof was shingles on t&g pine decking. Insulation was correct up versus that pine decking considering that 77 and is also 2014. Stuff looks like it was set up yesterday. Not a foul place any place, no roof vents absolutely unvented roof.
Your program to put in a stack of rigid foam rectangles in Every single rafter bay is called the "Slice-and-cobble" approach to insulation. It can be a way typically picked by homeowners, but never ever picked by insulation contractors.
If you intend to produce a ventilated insulated sloped roof assembly, select a style of air flow baffle that can be installed within an airtight fashion. Web page-constructed baffles are best.
The code constraints on the use of air-permeable insulation involving rafters had been created to circumvent the roof sheathing from rotting. When fiberglass batts are set up in unvented rafter bays, the batts allow for moist indoor air to reach the chilly roof sheathing.
The Risk is the fact inside humidity will migrate to the cold sheathing, bringing about condensation or moisture accumulation.
Must i totally aid sheathing seams parallel to your ridge line, for sheathing higher than an air gap? Would not that isolate the air less than Each the original source individual sheet of sheathing, and is usually that alright?