If you would like get it done ideal, you'll want to handle air leaks, tackle your recessed can dilemma, and insert enough R-value to at least meet up with minimum code specifications. It is a great deal of work, but it is not rocket science. Repairing these difficulties could possibly be high priced, however.
My opinion is that the steep facet of the mansard roof can be a roof. This can be very true if the exterior of your sloped assembly is finished with roofing.
U.S. setting up codes do not require using inside vapor barriers, even in chilly climates. Whatever they do demand is an interior vapor retarder. This necessity is usually happy with kraft experiencing on fiberglass batts or vapor-retarder paint.
Again for the vent notion. I really Believe venting a roof that's airsealed in the inside very well and designed without the need of vent chutes is possibly The easiest method to Develop cathedral ceilings.
Martin, I'm grateful for your time and energy, and soon after reading quite a few of your replies, I am able to see you are obsessed with constructing items correct. Suitable for people, and the Earth. Thank you for what you do!! Ryan Nelson
Electrical power codes establish minimum R-benefit needs for roofs and ceilings. There are many probable code compliance paths; most builders choose the prescriptive route, which sets forth minimal R-values for roofs and ceilings in a prescriptive table.
Most professional roof assemblies Do not hassle With all the fluffy stuff. They just meet up with 100% of your R-value requirements for your roof with rigid foam (both EPS or polyiso) and skip the batts totally. That is the way I counsel that you just move forward.
It is smart to ensure the top layer of sheathing can dry to the exterior when using rigid insulation on an unvented cathedral ceiling. But what about the suggested watertight underlayment for valleys, eaves, and reduced-slope sections of roof?
Another way so as to add R-value to your roof assembly is to incorporate 1 or 2 levels of rigid foam while in the roof assembly — both previously mentioned the roof sheathing or down below the rafters.
That you are proposing an unconventional approach to insulating your roof. If I recognize you accurately, you want to put in EPS involving the tops within your roof trusses and also your roof sheathing.
If Recommended Reading you like, you may Find your ventilation channels in addition to the roof sheathing instead of beneath the roof sheathing. If you decide to make this happen, Make certain that any roofing underlayment that you put in above the roof sheathing is vapor-permeable — by way of example, #15 asphalt felt, VaproShield SlopeShield, or Solitex Mento — and that your neighborhood developing Division accepts this method of roof venting.
I've a partial cathedral ceiling from the completed attic of my residence in zone four (TN). Just about every slope on the roof is split roughly in thirds by 3 distinctive cases: knee partitions within the outer thirds, "cathedral" ceiling in the middle thirds, along with a vented "attic" in the middle third with a ridge vent - a common situation with concluded attics, at the least around below. I have a major difficulty in the summertime with overheating. The insulation isn't really Doing work very well because it was inadequately insulated with just R-19 fiberglass batts between the rafters with no air flow baffle or suitable soffit venting and only r-19 blown into the "attic Area". Furthermore, my upstairs HVAC ducts are operate in the really hot "attic" House under the ridge. Dependant on what i haved acquired from numerous posts listed here, my prepared Alternative is always to cathedralize the whole roof, eave to ridge: install continous air-tight web page-designed 2" vent channels working with foil-confronted polyiso board (as advised in ), setting up continuous soffit vents to substantially Increase the airflow from soffit to ridge, developing an air-tight ceiling down below the rafters, and, most significantly, provide the ductwork inside the conditioned envelope.
I've a point for blueskin, for a equally an air and vapour barrier, but will also it will eventually act as a seal for your screws that maintain anything down. In reference to the vaulted schematics on This great site, it demonstrates vapour/air barrier on top of insulation, which got me asking yourself. Nearly as good as I'm installing resources, no person is perfect, and an air leak may develop among XPS seams. At the time ANY dampness will get all the way down to reduced sheathing, it's match more than.
Will it sound right to spray and Slice and cobble 4 inch shut cell foam/board on underside of sheathing followed by fiberglass inside the bays and 1 inch of eps/iso under the rafter (to halt thermal bridging) before ending with drywall? Will I make a vapor sandwich and greater leave the ultimate EPS and settle for the thermal bridging?