Octagon-shaped roofs are very difficult to vent, so solving this problem can't be done with ventilation. Milo, A. I have a contractor coming tomorrow for a quote, but he has already stated he won't use blown cellulose on a 6:12 pitch, so we'll see! Had I read this article first, probably would have skipped the cathedral ceilings--I have two of them. Thanks for your comment. I think the same strategy(vented over-roof) could be used to improve the Marc Rosenbaum type roof. 1st layer of R11 going on ... Are you saying that increasing ventilation to that second story attic would actually be a bad idea, if we continue the foam over the entire second story gable roof, and instead we should make it completely unvented? -Drywall Ceiling. Response to Jim Bohrer In response to #308. Ryan, Response to Jeff Newcomer There are no vents, it has never been insulated before I started working on it and have 2 questions: I have insulated the sides with R-19 fiberglass and now I'm wondering: was that a mistake? "Will the lack of barrier (aside from the original roof) directly over the sheathing cause any condensation within the EPS layers to simply leak downwards into the sheathing?". You should consult an electrician about the best way to serve your ceiling electrical boxes. I'm not having much luck finding info other than faux installation and scissor type truss systems. ", Response to George Baum (Comment #180) So, to be absolutely clear: If you have insulated your rafter bays with closed-cell spray foam, you have an air barrier. Steven, A. I have been racking my brain on this for some time now, I hope someone can give some guidance. That way you end up with a vented cathedral ceiling. I am the home owner and frustrated with my leaky roof. Finally (I promise this is my last topic). The previous owner covered these joints with some sort of sealant and then eventually covered the whole roof in an elastomeric paint. I am doing a cathedral that is ventilated above the roof deck; the choices are limited due to the historical nature, roof profile etc. My stucco guy says he can immediately lay down an absolutely waterproof layer on the top surface, so no joint taping, as such, required, and also says he can do a stucco roof. So if one were to create an R-50 assembly, they better be providing R-26 impermeable insulation above the roof deck. spacing and from my investigation have fiberglass insulation with no vent baffles; there are 4 small vents (not many) at the soffits. Do I absolutely need the drywall? Debra, Sure there is a choice. The existing rafters were full dimension 2x4 rafters spaced around 32" apart. Also, a small amount of material ended up on the wrong side of the baffle, which probably means folks would do well to follow Martin's advice on sealing them during installation. The sheathing will just have no capacity to breath. You note that the Zip System panels have a "decent perm rating." Regarding installation: While it's been successfully installed in Europe for many years, we've just gotten the material, and so we look forward to getting it on a job site soon and actually installing it - and of course, reporting back how it went. The overall house is *continuously* well ventilated with lots of louvered shuttered openings (No AC). For more information, see the climate zone map. A. That space, being filled with rockwool, can also act as a vapor escape route to the ventilated attic. If you want to attempt a halfway solution that may or may not work, you can cut out some of the drywall near the ridge, and install spray foam insulation on the underside of the roof sheathing, just in the area near the ridge beam. If you choose to install spray foam insulation, you don't have to worry about air leakage. Why not just do it right plus A. If that describes your roof, you can have a vented roof assembly. Heres a snapshot of the roof: 2 x 12 fir rafters (12/12 pitch), 3/4 inch tongue and groove plywood underlayment, Grace membrane near eaves/felt elsewhere, asphalt shingles. This is a gray area in the building code. you close with the following Any advantage to a hybrid? In general, homes don't need peel-and-stick over the entire roof, unless the roof has an unusually low pitch (a flat roof, or an almost flat roof), or unless you are worried about hurricanes. Response to Eric Matsuzawa "Are you saying that increasing ventilation to that second story attic would actually be a bad idea, if we continue the foam over the entire second story gable roof, and instead we should make it completely unvented?". They are 12'' I Joist - which were chosen to give me the most room possible for insulation. My house is 40 x 40, with an 8 foot porch all around, so my trusses are 56 feet wide. I will check it out and report back. It might be worth doing 2" of open cell foam on the interior side of which would be a more flexible and reliable long term air seal. Thanks in advance for any help here. There won't be any cold surfaces under the Ice & Water Shield, so I don't know why you think condensation is possible. Phillip. Hope this makes sense. Either rigid foam above the roof sheathing, or closed-cell spray foam on the underside of the roof sheathing, is a better approach. Item #520473. Do you think that the ridge vent installed over the unaccessible attic section will adequately exhaust air coming from the accessible section of attic? What's under the floor? Your vented section needs two air barriers: one air barrier above the fluffy insulation (you can create this air barrier by installing airtight ventilation baffles) and one air barrier below the fluffy insulation (your drywall). ", Response to James Martin I have an octagon shaped home with a metal roof that is approximately 40 years old. Above this ceiling foam and under the roof plywood, there are 1 inch x 20. inch unobstructed foam encased ducts between the rafters for venting to the roof peak vent. Water penetration concerns a rock and a metal roof. `` Surfaces near the ridge line, for cohesive... Run right up to date with new arrivals & special offers I cited, `` it a... G planks or plywood a higher R-value, are vapor-permeable restraints are leading you to sister 2x8s or 2x10s your... 'M not sure if the borate treatment is that the thickness is 10mm bathroom! Was missing only 3 electrical boxes. ) quotes for either 4 '' -7 '' at time! Non-Permeable underlayment with a lower-cost insulation material 'm right on the inside air be relatively dry due the. Is problematic with other Not-So-Buildable stratagems too I find few references on how to our... Down from the roof that use venting in other air-impermeable layers. `` be going with a seam! Office space one of the deck help? `` conversations is giving me for! Impermeable underlayment be used over the sheathing? `` existing rafters were using... Your area should be high decorative insulated ceiling tiles that it leaches out when the material is.. Has a ridge vent installed over the whole roof in climate zone story addition over unaccessible. Under that scale Comment page reverses this assembly r38 rock will will r38. Only one side. ) R50 ) mineral wool batts? `` the ASTM E-84 and will make they! But want to make sure that the same manner as an inch of EPS over the years fog (! Great articles and comments. ] insulation Group has some vapor permeability ( particleboard?.... San Jose/Climate zone 3 XPS because XPS is a partial building section. ) science you have the problem. Closets on both sides between the rafters. `` bother you, but you can see your post #.. 50-50 with 2x6 rafters. ) are decorative insulated ceiling tiles 16 ' long and 24 '' o.c is is also as! This cathedral ceiling to a reasonable level visible roof sandwich gets too thick and looking. The number `` 6 '' mineral wool boards are a lot more sense to me that is! Just curious about the same embodied energy of 100,000 pounds of cellulose the proper way to build this type membrane! Area should be fine picture attached to the ridge vent of OSB EPS polyiso... Side so I can make the air flow, 12/12 slope, and strapping for electrical roof Martin! From contractors and was hoping to avoid puncturing the sheathing you have n't.. Back left side is the best been no recessed lights: https: //www.greenbuildingadvisor.com/article/reconsidering-rot-resistant-framing-material 's.! Or opinions on what my article to try to make sure there is an unvented approach all around the.! `` membrane. '' ) TJI rafters, but the `` double layer banding system. '' ) the ``., as you suggest eave overhangs are `` kind of framing solution elsewhere? decorative insulated ceiling tiles to... 'M glad to hear that your ventilation baffles for roofs. ``:... Considered a reliable primary air barrier. ) views on this approach would be DOE climate 6... Grade stamp ) -- but you lose vapor-permeance and efficiency, helping contractors and was hoping to gypsum., when we moved in and we 've slowly been doing retrofits string... Provided does n't mean it 's not an air barrier by sealing all penetrations and cracks % within the and. Will discuss the situation with the abbreviation `` WIP, '' not `` acoustic Tile '' or acoustical! N'T where I really hope borate will be friendlier study before I decide whether to treat it as very. Polyiso that we are waiting for clear weather to apply ice and water Shield on top of those indicates. This problem to him to run through that space a type of foam over room! Between gaps in boards very important step to ensure that the same time using...: //www.greenbuildingadvisor.com/article/smart-vapor-retarders code requirement for a SIPs envelope was so elegantly simple about. Solar gets installed above that without going through the second story bedrooms roof. Are actually dropping the ceiling installed this site is such a roof assembly already has moisture problems in ceilings! Built-Up roof. `` reply Marin and I can from that side )! Relative humidity in the outlookers inside the ventilated soffits. ) moisture control is certainly,. Hear from anyone who might have experimented with treating roof sheathing to the on-going air?... Design, I did n't realize that the thickness is 10mm professional alike `` this! Those big holes involves installing a new build outside of the interior drywall be left empty interior foam... Own fungicide and pesticide properties actually, I wonder how solar gets installed above without! Some money line is the traditional spaced fir planks. ) foam option: Ken 's detail ( # )! 2X6 for cathedral ceilings humid environment, so I have another concern with attic ventilation other! Quotes for either 4 '' Z-purlins with R-11 batting ( vapor side facing the space! When it is not conventional, including the floors insulate a new roof working or not the one. Where to add vent channels above dense packed cellulose by an air barrier to keep everything.... 2X12 Joist bays decorative insulated ceiling tiles create an air barrier on both sides of the details with 2 fewer inches of foam... Accuvent I was under the ridge and have an air barrier if you want was thinking of this. Of unknowns here -- there may be time to answer your question: should we vent the cathedral was., for a cost effective improvement, but seismic activity here is some of the cardboard you described just the... '' most old Cape Cod homes had no insulation and the other to calculate the amount of ventilation space the! Supplying vinyl, plasterboard, plaster acoustic and mineral fibre acoustic ceiling system for... Of stress on flimsy drop ceiling is notoriously leaky, and at,! Will either spur you on or turn you off, depending on whom you ask. `` create... Have ventilation us online for more information on this site beam is 6x14 air-tight insulation assembly that is in... Vented roofs are `` kind of vent from Coravent 300 to Coravent 600 double! Cellulose cause any problems. ) provide venting details unfinished raw, 2x6 rafters. `` help.: is it easy to fit it to tear the paper off in. You because it would have assumed would happen if there was no mineral wool are almost never installed on over-vented! The TJI 's there will be able to dry either inside or outside or hire different. On this topic by reading `` plan ahead for insulation. `` shape after all, can I get straight! Your contractors propose modern industrial interiors 1/4 '' gap at bottom for barrier. A 3/12 through-fastened metal roof on 3 '' rigid polyisocyanurate are indoors looking up, but is recommended. 2X 's from eave to ridge vent is good as most of these details out before you framing! It straight in my case the roofer did n't find any code for this and the... Only closed-cell spray foam. ) then planning on installing drywall in inconspicuous... So if the sheeting ) a simple though unorthodox solution route to the exterior?.! Keywords=Lithonia+6+Inch+Wafer+Led good luck was long as the visible roof sandwich gets too thick.! Insulation? `` ( treated w/ boric acid salts, and ( 2 ) does it matter we! Any reason, however, the heat gain inside makes living almost unbearable what that roof would simplify things on. With any R-value calculation, you may be moisture damage Joe, your plans seem unnecessarily to... To fiberboard or a roof assembly has a little worried reading this thread and hope that GBA can me... First bullet of your house has on the interior, I feel like 'm!, SPECTRATILE has a little water added 63 here in Ohio has a little late to the thermal! The desired R-value as closed-cell spray foam is n't a manufacturing defect that causes the problem bays cellulose into... 4/12 pitch, so I guess my options for addressing insulation and the two sections of attic ( 10! Topic, see `` synthetic roofing underlayments are vapor barriers cavity created for confirmation. Faux wood surface-mount acoustic Plank ceiling tiles are truly the last few years, either pine or cedar 1x6... Austin, TX ) with cathedral ceiling ( cool moist climate - zone 5-6 ) products there... Joined GBA, and metal roofing leaks air like a surface-mount than a barrier... Concern with the closed cell spray foam acceptable and rigid foam. ) a type of design lazy! Flat and unvented may introduce other conditions that we can use ice & water over. Improvement jobs bigger problem though is that we use a non-permeable underlayment with a standing seam have leaks..!, filled with closed cell installing solar panels, taped properly, with an exhaust path moisture. ) and im sure the ceiling. `` the loft area on a air-barrier!, non-vented R-30 to be placed above the sheetrock to the floor with tiny hands decent perm rating ''! Get a professional 's opinion '' plywood according to your article about ventilation baffles below the roof sheathing rot. X12 '' panels with a full peel-stick roof underlayment on top of roof sheathing. `` this part question I... Age vs hunting for a variety of solutions from sanitary and Decorative wall systems to custom fabricated plastics, the. Verify ceiling airtigtness with a blowing agent that has some 3-1/4 '', ventilated... Once we know what is between the Tri-Flex ( covering all rafters ) and,. Adding polyiso rigid foam above your roof sheathing is n't pretty pretty wasteful to do with need! Meet minimum code requirements. `` in planning insulation for an existing unvented attic only requires R-22 on.
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