If you'd like to put in a mix of rigid foam in addition to your roof sheathing and air-permeable insulation involving your rafters, you'll want to make certain that your rigid foam is thick ample to maintain your roof sheathing higher than the dew position.
What received me started within the "air tight walls and roof sheathing" was your report of precisely the same title; particularly South Mountain Company's fantastic report on the Martha's Vineyard housing enhancement. I saw Marc's presentation on Individuals homes at BBD also.
Also, would not the website-designed plywood baffles concerning the rafters hold the same difficulty; slow drying through diffusion? ( I suppose I could use fiberboard for baffles)
I happen to be making use of rigid breadboard design expanded polystyrene inside the rim joists and thought precisely the same might be place under the sheathing among the rafter bays, and with any gaps sealed having a urethane spray foam for instance Fill and Seal. Is there a high quality which makes spray foam appropriate and rigid foam unacceptable?
If you want to produce a ventilated insulated sloped roof assembly, opt for a kind of ventilation baffle that can be put in in an airtight fashion. Web site-created baffles are very best.
Martin, Thanks on your reply. Those people content articles are both equally pretty informative. I am receiving the feeling that SIPs can be done nicely, but may be beat in rate with exterior from this source rigid foam programs while you've suggested, with equivalent or much better performance (with emphasis on air-tightness).
I'm not a fan of whole peel-and-adhere roofs, for a variety of good reasons. But your program will most likely be great. Just Make certain that your roof sheathing is dry to the working day you install spray polyurethane foam -- as the sheathing won't be drying greatly in either direction following it's encapsulated among peel-and-stick membrane and spray resource foam.
A. There's a code prerequisite for a vapor retarder in certain varieties of assemblies, but there's no necessity for just a vapor barrier. Your layer of rigid foam is presently a vapor retarder. No further vapor retarding layer should be installed.
1. It's always a foul plan to set up an HRV within an attic. HRVs have to be accessible ample to the homeowners to routinely alter the filter.
"R-19 batts are really air permeable, and on lengthy unobstructed rafter bays you have got very a stack influence. It would not have a enormous amount of air leakage to offer some drying there. Also, If your batts are unfaced or kraft-confronted, the drying towards the inside might be sizeable.
My view would be that the steep side of a mansard roof is a roof. This is often especially true if the outside in the sloped assembly is completed with roofing.
. Unvented roof assemblies are Protected. The primary reason that a number of people put in air flow channels earlier mentioned the rigid foam is given that they are in spots with many snowfall, and they like a "cold roof" to attenuate ice damming complications. Thanks for your remark. I will edit my write-up to try to clarify any ambiguity on this issue. .
If you're picking out to develop a vented roof assembly, don’t fail to remember to incorporate soffit vents and ridge vents.
We have made a decision to insulate on the outside from the roof sheathing the many way across both sides from the gable roof, as a way to match up the roof strains.