Cellulose insulation can retail store lots of humidity. This "humidity buffering" ability is cited by some cellulose enthusiasts as A significant advantage, and certainly this capacity can in some cases reduce a small moisture dilemma from creating a lot of rot.
Keep in mind: if you choose to put in rigid foam on top of your roof sheathing, don’t set up ventilation channels under the roof sheathing; both of these tactics are incompatible.
If you decide not to extend the rigid foam above the parts of your roof that have a standard vented attic, your builder (or an architect) can come up with a trim detail which you may be able to Are living with.
A. To reap the benefits of the insulating value of the rigid foam in excess of the attic, you definitely want to seal up any attic vents, therefore you definitely don't desire to make a ridge vent.
It's fine so as to add foam board over the roof deck Despite having the shut mobile foam-board (what kind?) on the inside. Roof decks can't dry to the exterior by way of 0.one per shingles in any case, specifically because in zone five it will devote a major amount of time protected in snow/dew/rain Along with the moisture generate heading inward, not outward.
You will be proposing a vented roof assembly. To get a vented roof assembly, the code will not involve that any foam insulation be positioned in immediate contact with your roof sheathing -- Quite the opposite.
I've a factor for blueskin, as a the two an air and vapour barrier, but additionally it will eventually work as a seal for that screws that maintain everything down. In reference to the vaulted schematics on This website, it exhibits vapour/air barrier in addition to insulation, which bought me wanting to know. As good Resources as I'm setting up supplies, no one is perfect, and an air leak may well create between XPS seams. The moment ANY dampness gets right down to decrease sheathing, it truly is recreation about.
Be sure to put in insulation that provides at the very least the least code necessity for ceiling R-value. Insulation that exceeds the least code requirement is better yet.
Q. "I have lately obtained usage of cheap roofing polyiso -- black backing on either side. My feeling is always that putting this backing from the rafters in connection with that vented air may be see here now inviting a mold issue, and if i confront it towards the home i reduce the radiant barrier."
If I understand effectively, you might have just completed putting in some recessed can lights, and now you need to know the way to insulate close to and over these can lights. Your intention is to set up a new complete ceiling, beneath the rafters, as soon as the insulation is mounted. Is appropriate?
Ensure the roof assembly is as near to airtight as you may make it. For anyone who is making use of fluffy insulation, you require two air limitations: just one underneath the insulation, and additional hints one above the insulation.
As Monthly bill Rose notes, air tightness of your assembly, both equally inside of and out, is of significant worth - we have to halt the air circulation. As a result I might suggest an assembly that makes use of elements meant to supply air tightness whilst also maximizing the drying possible with the roof assembly. The element illustration I've connected demonstrates these an method. Solitex Mento a thousand membrane is used on the skin of your insulation - a vapor open, but water and air-limited product - with vented cavity earlier mentioned - permitting for optimum drying out and preventing any wind/air penetration in the insulation.
I am sorry to generally be the bearer of poor news, although the sections of roof that are insulated with six inches of fiberglass and inside polyethylene weren't insulated the right way. In These sections, the roof sheathing is prone to dampness accumulation and decay.
Having said that, I feel you will be Mistaken regarding your asphalt felt; I question In the event the felt is impermeable to water vapor. Most types of asphalt felt are to some degree permeable -- commonly five perms when dry and around 60 perms when wet.