2. Set up strong web-site-developed ventilation baffles in Every single rafter bay before you spray the foam. That way you end up with a vented cathedral ceiling.
You do not need to work with insect screen, mainly because fiberglass batts have to be enclosed by an air barrier on both sides. When the major aspect of fiberglass batts are topic to wind-washing, the going air degrades the overall performance with the insulation.
Most of the knowledge I run across appears to be within the cellulose industry that promises wind-wash is an enormous difficulty with fiberglass; and in the fiberglass business which asserts the cellulose team overstates the issue and that on the extent wind-clean happens it is de facto inconsequential.
Most rafters aren’t deep plenty of to support the insulation necessary to fulfill least R-values necessary by code, particularly when the rafter bays contain a ventilation channel.
Thanks with the suggestions. We won't ever A/C the creating (It'll be photo voltaic powered). The wind is really constant, but it is a humid environment, so dampness Manage is absolutely on my thoughts.
I've a number of queries that incorporate many of the matters that you have covered in these articles or blog posts, but I am trying to apply them in a retrofit situation. We are working on upgrading the Electrical power efficiency, together with extra/updating insulation, for our Pretty much 100 12 months old 2-one/2 Tale balloon frame household (stucco in excess of lathe exterior).
Code interpretations are subject on the resolve of your neighborhood building inspector. In the end, it would not subject what I think -- what matters is exactly what your neighborhood code Formal thinks. So inquire her or him.
As making scientist Monthly bill Rose has proven, code demands for roof venting had been never ever based on research or scientific ideas. In a very properly documented JLC
You say "You don't need an inside vapor barrier," but In addition, you mention that "you need a very good air barrier on both his explanation sides of your respective fiberglass batts." The latter would transform an interior vapor barrier not so?
1. You don't need an inside vapor barrier. In a very sizzling humid weather, the vapor generate is always from the outside towards the interior (assuming click over here now your building is air conditioned). If the setting up just isn't at any time gonna be air conditioned, the vapor travel will nonetheless be from the outside to the inside, but there won't be Significantly vapor drive.
I am a homeowner in Seattle. Have a freshly-framed, vented cathedral ceiling to insulate. Straight bays, 2x12, 24" o/c. The existing prepare is to make use of batts of some sort during the bays, take care to air seal the inside floor, avoid penetrations, air seal the vent channel much too (bays thoroughly sealed), double primary the inside floor for vapor resistance. I've a pair questions about baffling the vent channel: one. Some of the setting up experts I am dealing with experience the jury is still out on baffles and so are recommending leaving the batts open up on the channel besides close to the vents, assuming the one-2" air channel is usually taken care of.
Therefore the query is: seal the stucco vents and incorporate the spray foam roof and Don't fret about condensation? There exists little reduced-hanging fruit inside our sort of design, Specifically on existing houses, Which explains why folks are remaining sucked into the spray foam roof fraud.
. Unvented roof assemblies are Risk-free. The main reason that many people install ventilation channels above the rigid foam is as they reside in places with lots of snowfall, and they prefer a "chilly roof" to minimize ice damming complications. Many thanks to your remark. I'll edit my short article to try to explain any ambiguity on this issue. .
Joe Lstiburek: "A vented attic, the place insulation is placed on an air-sealed attic floor, is Just about the most underappreciated creating assemblies that We have now during the historical past of setting up science."