b vent through drywall ceiling

Please consider supporting our work with a contribution to wikiHow. Martin, If you intend to install EnGard insulation batts in an unvented cathedral ceiling, you'll need to have a significant layer of rigid foam insulation above the roof sheathing. The first clue is usually a ceiling stain or ceiling drips. The air barrier will be poly attached with sealant and internal finish will be drywall. Most roofers in the area use 100% ice and water shield. Speaking of treatments they studied, the results vary from bad to pretty good. I'm familiar with that approach and have used it on previous double walls with flat ceiling/ truss roof assemblies. Yes, you can insulate your horizontal ceilings with fiberglass batts (although cellulose would be much better, because cellulose fills all the nooks and crannies, and does a better job of limiting air leakage). install ceiling of taped sheetrock The roof rafters are 2” x 6” with 16” o.c. >"Thinking possibly 2 inch polyviso in bays to create 1.5in vented space then another layer of 4inch xps across rafters. It's a tempting idea, because that would bump the nominal R Value of the assembly to R-30. Great thread on insulated cathedral ceilings! Also, is there a GBA Drawing in the Library for this ....or something similar? Martin, thanks again. So at Bill's suggestion Jim Millhouse (also from National Fiber) and I ran a couple of 'tests'. Thanks, Martin. wikiHow is where trusted research and expert knowledge come together. The cathedral ceilings of the 1970s and 1980s were thermal disasters. This assembly seems like it would have poor drying potential and as such taping the seams of the polyiso seems like a bad idea. Total insulation below R49 isn't really a viable option either so I'm trying to sort out the best path forward with what I have and I'm open to suggestions. None of them have talked about adding an air barrier layer above the T&G. I have no knowledge of anything like this being implemented elsewhere.". Could you please confirm whether it is OK to use this hybrid approach to a roof assembly (make it part vented and part unvented)? The danger is that interior moisture will migrate to the cold sheathing, leading to condensation or moisture accumulation. The method shown in the video is particularly appropriate for builders in climates subject to ice dams. Closed cell foam that thick is also an air barrier, and a class-II (almost a class-I) vapor retarder, which keeps moisture from reaching the roof deck as well. As mentioned above, we hope to replace the roof this next year. the ridge of the roof is above the attic. Debra, Right for people, and the planet. What makes adding insulation to the roof worse? It will probably be less than 5.25 inches thick. The last image shows a large 10' overhang. It's hard to find good resources for this stuff. If you choose to install open-cell spray foam instead of closed-cell spray foam, your roof assembly will be able to dry somewhat to the interior. I think that most contractors would worry about the buildability of your approach. Either plywood with taped seams, OSB with taped seams, or one of the European membranes (or one of the U.S.-made synthetic roofing underlayments -- especially those advertised as air barriers) would be a better choice. Install electrical boxes at the locations where your surface-mounted fixtures will be installed. (I'm Martin.). If a builder really wants roof sheathing to be able to dry outward, it's always possible to create ventilation channels above the roof sheathing. Loring, Sounds reasonable so that’s the way we are going to proceed. The second problem is that not all building inspectors will accept the "above-the-roof-sheathing vent channel" approach, and may deem that your proposed roof assembly is non-compliant. As the house flexes with changes of temperature it's possible, even likely that some of the foamed-in air sealing will leak. I am currently replacing all my old leaky cans with those. And Martin, I hear your concern that its permeability is only 0.04 so it won't allow outward drying. I'd like to get to at least R60. It is also obvious that products with mouldicides (e.g., Boracol 20-2BD and Kilz®paint) perform better than wood preservatives primarily designed to stop (Copper and Zinc Napthenate). : ), If I changed my venting detail to a site built style, between the rafters, as in your many blogs on this topic, my air barrier would need to transition back inside before it got to the sloped roof; very cumbersome at the gable walls. I am in the throes of building a straw bale house...bales in and scratch coat of hydraulic lime plaster on. Give up any idea you might have of forcing the sheets into place. The existing: hip rafters, ridge, continuously connected top plate of wall perimeter are all i-beam construction, welded together & to each adjoining member. Kathryn It sounds like I should pull down the fiberglass and have it spray-foamed before I drywall. I think you mean this: Your cathedral ceiling is presently uninsulated. For the walls I'll be taping the housewrap. "Would it be OK to use another layer of foil faced polyiso (vapor-impermeable)? But if you live anywhere colder than Zone 3, you would need more rigid foam. I suggest that you post your question on GBA's Q&A page. Seems there are several options for us here. We were planing on R-36 batts then T&G for the ceiling which gets us well over the roof code. Board insulation under the rafters would make it like a cathedral ceiling. A 1000 SQ Ft basement (assuming 20X50) would run you $707 in ceiling link parts, $40 in screws and $700 to 900 in panels (2' X 4'). The point of the ventilation gap is not the encourage moisture to flow out of your ceiling. (Some building codes require a minimum of R-38 in Zone 2.). Hi folks, I'm back again having spent quite a bit of time working through the pre-cutting construction phase of my small cabin. If you use a ductless range hood, remember to change out the filter about every 3 months. Straight bays, 2x12, 24" o/c. Should I treat the flat roof as a cathedral ceiling and go with spray foam (or board), fiberglass, and no moisture barrier? However, as good as that could end up looking, I am a purist at heart and don't like the idea of the plywood only being for aesthetics - not to mention the additional costs involved. Martin, It would simplify soffit and rake venting. Also, being somewhat on a budget, I am reluctant to hire a contractor just for that purpose, and the two-component DIY kits do not look promising. (For more information of this topic, see "It’s OK to Skimp On Insulation, Icynene Says. In most cases, renovation work can be performed without bringing all aspects of your house up to current code requirements. You may need a friend on hand to help you lift the hood into position. Would I also have to do the polyiso against the knee wall? Would it be useful to install a layer of peel and stick? ". Conceptually, some additional air handler air bypassing the evaporator coil (which will increase duct temperature) is another way of addressing the problem. The vent channel above the rigid insulation may reduce the chance of ice dams, but that vent channel doesn't make your roof assembly vented. 1. with 5" of foam, wouldn't there be an air gap of one inch or so between foam and polyiso, and would that be okay? This image is not<\/b> licensed under the Creative Commons license applied to text content and some other images posted to the wikiHow website. Right now rafter bays are insulated with kraft faced r-11 fiberglass batts. The rest would be fiberglass bats and then the rigid board. Alternatively, we could forego a self-adhering layer and go with a synthetic underlayment attached directly to the old built-up roof underneath all layers of foam. Q. I'm in Boston so it sounds like I need R-20, which is about 3 inches of spray foam, right? That leads me back to just using the plywood as the ceiling and wondering if the spray foam insulation and thick and heavily insulated ceiling cavity might be enough to combat air intrusion up to the roof sheathing? If that describes your roof, you can have a vented roof assembly. Install the boxes carefully, and verify ceiling airtigtness with a blower door test. A. Solitex Mento might work, if you can figure out how to use it as a ventilation baffle. I figure the gap between the beam and drywall needs to be sealed and I also want to clean up the look of the beam by sanding off the water stains. We don’t have any major concerns on the vented attic side, but we are having a hard time deciding what to do about the cathedral ceiling. The roof is going to be done in perhaps 4 sections so may try rigid foam and spray foam to compare what works. As I noted in my last reply, I wrote an article on this topic ("Three Code-Approved Tricks for Reducing Insulation Thickness") that provides several code-approved approaches for cathedral ceilings that allow less than R-49. What are my options for addressing insulation and air sealing from inside the envelope? A. thnx More information on Option 1 here: "How to Install Rigid Foam On Top of Roof Sheathing.". The unaccessible attic on the back left side is the area of concern. You'll want to look at gimbal options if you want to avoid the lights playing lightsabers across the room. So inspections aren't an issue. is that something to be concerned with when creating the bond break? Many kinds of construction products include paper, so I wouldn't worry. - no insulation If you pay attention to airtightness, you shouldn't have any moisture worries. I live in WI and my roof has asphalt shingles. Martin, Mason, Q:What's under the floor? Thanks for your comment. For example, you can install a continuous layer of rigid foam on the exterior side of the roof sheathing, or you can install framing members at 90 degrees to the rafters, on the interior side of the rafters, to deepen the rafter cavities.". I plan to wrap the outside of the exterior rigid insulation with peel and stick membrane. A third firefighter brought up a chain saw to the roof. There are lots of alternative approaches, and they are explained in my article. If you think you can vent part of your roof, remember that every single rafter bay needs a clear channel, from the soffit to the ridge, with no impediments. Get a couple of pipe elbows to connect multiple vent pipes. A. No cans. No. Andre, I'm preparing to build an unvented vaulted roof assembly in zone 5, and I'm trying to find the best way to get the right ratio of rigid foam above deck to fluffy insulation between the rafters, to meet or exceed code (now and if/when the rigid insulation loses R-value). but it appears that the areas that were packed with cellulose(lower left) show less damage. But ideally you'd have the air barrier on the underside of trusses, then strapping, then your drywall to allow for elec and non-puncturing LED puck lights. Assuming that we do not vent, does it matter that we use a non-permeable underlayment with a non-permeable metal roof? sips are great but in the coldest of climates they have encountered problems. Yes, that's OK -- people do it all the time. Q. I can feel roofing paper between gaps in boards. I plan to convert my attic into conditioned space for housing a heat-pump air handler and associated ducts. going to lay down 2x4's 16 o.c mid way in foam. Builder wanted to go the vented route, which can still be done, it has a ridge vent and eaves vent. Is this best practice? If you’re installing through a finished wall, measure a nearby doorway, then add extra length for insulation and other components. Martin, thank you again for your comment. "Can I use rigid insulation below interior plaster finish to increase R-values? Your approach will work. The other pipe connects to it and runs horizontally towards the outside. That would work. Ideally, you would install between R-20 and R-25 of rigid foam above your roof sheathing before installing a new roof. That doesn't seem like it would work? Makes a good reference point. • The air in the ventilation channels is often warmer than outdoor air, a fact which limits condensation; and In central Texas, your winters are mild -- so you have fewer reasons to worry about condensation, moisture accumulation, or frost on the underside of your sheathing than homeowners in Minnesota or Maine. 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Expert knowledge come together require the use of XPS - 30psi reach the roof. `` inside, as are... Partition walls can go back inside the new roof design as a vapor barrier not so?.! Assess the current R=20 insulation ( cellulose or mineral wool externally ( ComfortBoard... No valleys, no roof vents completely unvented roof question Martin, thanks for the invaluable information on acceptable to. To shovel the entire void fairly tightly between the spray foam. ) flash-and-batt method increase the where. Try testing the route yourself of gyp those layers given my climate zone of! Widely available them knowing that plywood ) and do n't know about the electrical the. Barrier '' is n't enough foam in rafter bays wide a ridiculously small budget even! A 20 % failure rate 2x14 was my thought space and no vaulted ceilings, low-slope & lighting! Are all options for addressing insulation and other chemicals released during the installation in a separate VB with...