Your prepare to put in eight inches of rigid foam is a superb a person, however you could possibly put in thinner foam if there is a compelling rationale to take action. Obviously, eight inches of rigid foam has the next R-benefit, and will complete greater, than a thinner layer.
The most crucial flaw During this roof looks to be the ice and h2o membrane at the very best level within the rafter bays. Would just frequent felt paper have authorized more than enough moisture to dissipate with the roof sheathing steering clear of rot?, I type of question it.
Until eventually lately, making codes demanded that insulated sloped roofs incorporate ventilation channels specifically beneath the roof sheathing. Numerous builders nonetheless adhere to this time-examined method.
Q. "Ought to I Chunk the bullet and threat of spray foam insulation, or send the builders back up over the roof in December to cut ridge and soffit vents?"
Q. "I've not long ago received access to affordable roofing polyiso -- black backing on both sides. My emotion is usually that putting this backing from the rafters in connection with that vented air might be inviting a mold problem, and when i face it to the space i reduce the radiant barrier."
As I explained in the article on this web page, You cannot use fluffy (air-permeable) insulation within an unvented roof assembly Except you contain rigid foam or spray foam above the fluffy insulation.
A. It is smart to you because it meets your needs. As you are mindful, it isn't really a perfect way to insulate your roof assembly. But you have described it as A short lived quit-hole measure.
The for a longer time that you choose to wait to install rigid foam higher than your roof sheathing just after your rafter bays are filled with fluffy insulation, the larger the chance that your roof sheathing will accumulate moisture. 1 or 2 decades really should be no dilemma, but I wouldn't extend the work out A lot farther than that.
I've a mansard roof with steep sides with gables, and a virtually flat top rated using a rubber roof. There won't be any vents, it has not been insulated right before I began focusing on it and possess two issues:
It is smart to make certain the top layer of sheathing can dry to the exterior when working with rigid insulation on an unvented cathedral ceiling. But what about the proposed waterproof underlayment for valleys, eaves, and minimal-slope sections of roof?
It's Harmless to state that an More Help current house doesn't have very good roof ventilation if there are no soffit vents my website or ridge vents. It's also Risk-free to say that, even though you will find soffit vents and ridge vents, the roof isn't ventilated if it involves valleys, hips, dormers, or skylights.
If We'll put some insulation earlier mentioned the ceiling, then I would like to put The many insulation previously mentioned the ceiling, and steer clear of the Expense and headache of a brand new decreased ceiling. Meaning a Construct-up of 8", utilizing XPS. If we Establish up the roof line higher than the cathedral ceiling in the family members place by 8", we presumably need to create up the remainder of the adjoining gable roof likewise.
During the summer, roof her latest blog ventilation will not substantially decreased the temperature of asphalt shingles or other kinds of roofing.
Very first, could it be simple to recognize whether a roof is ventilated? If no soffit vents or facet vents are visible around the roof from the ground, does that signify the roof just isn't ventilated?