I have an idea of what to do, but the more I read the more I realize I don't want to get this wrong. Four inches of closed-cell spray foam -- the thickness you plan to use -- will work for Climate Zone 6 (or anywhere warmer), but you will need thicker spray foam if you are located in Zone 7 or 8. Thanks Martin, As a result, my exterior walls are 2x4 so I'm looking at mineral wool batts between the studs as well as rockboard 80 installed on the exterior sheathing. There had to be some major air leaks in the air barrier to show this kind of damage. Seth, - rough sawn 1x12 sheathing Another question: we currently have blown-in cellulose to level R-38 on the floor of the attic above the second story bedrooms. Martin, This concerns me...any thoughts? The R5 thermal break on the rafters would improve the framing fraction performance to something comparable to (a bit better than, actually) a 2 x 12 rafter bringing it close enough to code on a U-factor basis (which is anything under U0.026, or R38.5 "whole assembly) and there would still be adequate dew point control at the foam/fiber boundary to be able to use interior latex on ceiling gypsum as the interior side vapor retarder. This means that the insulation in the roof has to project out as far as the external insulation. "Would it be at all possible at all to use something as Loctite TiteFoam (which, as the company rep stated in the HD Q&A section, is closed-cell, although I am not sure if that is correct), or any other one-component closed-cell PU spray foam product for that matter, instead of a 2-component kit?". That's why my article notes, "if the geometry of your roof is complicated â with features like hips, valleys, and dormers â itâs impossible to assure air flow through all of your rafter bays.". It also means that your roof assembly is illegal, because you need an effective ventilation channel above the top of your cellulose layer to meet code requirements. Any rafter bay that can't be vented needs an unvented approach. Then install either 2x4 purlins, 24 inches on center, to support your metal roofing, or a second layer of OSB or plywood roof sheathing above the new rigid foam. I can say we are not selling these products at arms length, we are working closely with the architects and builders on these projects. That's complicated and expensive. ", Q. That's because these hearths reach much higher temperatures and as a result, need the added protection to prevent too much heat escaping from the chimney as radiant heat. Some of the suggestions may also apply to the venting pipes that extend above the roof of a home or business. In this âdry-to-the-interiorâ solution, is this the right place for the underlayment? I'll also request that we get airtight fixtures to minimize air infiltration around the fixtures. Stucco isn't roofing. ", https://www.amazon.com/Lithonia-Lighting-WF6-LED-30K/dp/B01ND1L263/ref=sr_1_3?ie=UTF8&qid=1547220349&sr=8-3&keywords=lithonia+6+inch+wafer+led, "Three Code-Approved Tricks for Reducing Insulation Thickness", https://www.greenbuildingadvisor.com/question/home-brew-wood-preservative, https://www.greenbuildingadvisor.com/article/reconsidering-rot-resistant-framing-material, http://pacificmoldprevention.com/-raise-the-ph.html, https://www.buildsite.com/pdf/owenscorning/Owens-Corning-FOAMULAR-XPS-Roof-Insulation-for-Commercial-Buildings-Summary-Brochure-1235135.pdf, "Combining Exterior Rigid Foam With Fluffy Insulation. I guess the best course of action would be to just do a drywall ceiling and then skin it with 1/4" plywood. Jaime, try to make sure soffits are sealed off from the inside as best as possible. Here is the link to my answer: can I do it with out drywall? I would love hear from anyone who might have experimented with treating roof sheathing or other structural components with borates and/or glycols. The main flaw in this roof looks to be the ice and water membrane at the highest point in the rafter bays. Q. During the winter, the moving cold air pulls heat out of the fiberglass batts as it moves by. That's correct Malcom. The drywall in that area was originally installed using some spacers here and there between it and the rafters. Would this low an R value end up producing condensation on the interior face of the spray foam? If you want to read this code section in detail, here is the link: 2015 IRC - Roof and ceiling construction. Response to Milo Shubat "As little as an inch of closed cell polyurethane (R6-R7) on the underside of the roof deck would be enough dew point control.." - Synthetic underlayment stretched over roof framing I wouldnât want to do it. Many thanks for any input, each time I think I've got a handle on the requirements a little detail comes up that makes me reconsider something else... R. Kirkby, Q. Existing is a fourteen year old roof with 2" of closed cell roofing foam with an acrylic elastomeric coating. Response to Alan B (Comment #181) The GBA website does not provide custom details. We are in Boston area and are adding a family room and master suite with cathedral ceilings, though the bathroom and walk-in closet will have an attic where HVAC is installed.. Ceilings (including ceiling above the attic) will be insulated with R-49 faced fiberglass and will be vented. That's just 50 cents per square foot and getting darn close to price of fiberglass batt. Response to Albert Rooks If you want to install an HRV in your attic, why do you need to install a waterproof stucco roof over some type of EPS box? So with that in mind, what are your suggestions for this 3 feet of space? Either method would work, although the use of closed-cell spray foam is often avoided by green builders (unless you specify one of the new types of closed-cell spray foam that uses a blowing agent with a low global warming potential; for more information on this topic, see Next Generation Spray Foams Trickle into the Market). Would I also have to do the polyiso against the knee wall? I would call this an insulated attic. "If you have a wool infill insulation, and you can sheathe it with something that has some vapor permeability (particleboard?)?". If you build your ceiling that way, you will be plagued by air leaks for the life of the house. The reason to put the additional insulation in contact with the underside of the roof is that it's hard to verify that you have successfully closed off all vents to the attic. Thanks for this great discussion! First it is very difficult to stop all airflow, especially with conventional traditional practices (ie chimney and plumbing vent penetrations through the roof) We have several techniques developed over the years to seal the vb at the eaves and gables, but there are still nail penetrations through the vb. If you have vapor-impermeable roofing on the exterior side of your steep mansard roofs, you definitely can't insulate these roofs as if they were walls -- because these assemblies can't dry to the exterior. 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. If it's 2x10 rafters 2" of closed cell (R13-ish) would leave just enough space for an R30 rock wool batt, for R43 total. Thank you for your help and sharing your knowledge! Hello there, Now, as I mentioned, several rafter bays (the longest ones being just over 8') hit the hip ridge on both sides at 45 degrees. One roofing contractor wants to remove the foam completely along with the tar and gravel roof and then install the new metal directly onto the decking. I'm starting to wonder if going with a TPO roof would simplify things. From out to in: Shingles, Membrane, Sheathing, Closed-Cell Spray, Batt, Gyp. Seems that R-49 is R-49, shouldn't matter if blown or closed cell. Would I need to directly connect the chimney pipe to the insert or would the existing exhaust into the zero clearance be sufficient? This membrane needs taped seams. and will 2 layers of R11 be too much to compress in my 4" purlin space (I realize that codes in the US call for more insulation, but I will have a good amount of cool breeze flowing through my house). Will using R-15 CCFoam + R15 Batt meet the requirement. Would be grateful for comments either way as to why not to use mineral wool there, or alternatively how to use it properly to avoid whatever the issues are. First, thanks Martin for the wealth of knowledge this website has. You could skip the tape on the top layer of plywood to same some time and money. I'd like to use the exterior wall and roof sheathing as my primary air barrier; cdx plywood with all seams taped, which sort of forces me to keep the roof venting on top of the roof sheathing, as you describe in paragraph 7 of this article. The t & g has to be thick enough (1x or thicker) to qualify as a thermal barrier against ignition of the foam, but half-inch gypsum board qualifies on it's own. I will look closer into it before I decide whether to do anything extra. If the moisture content of the roof deck is low when re-roofing (measure it- under 20% is good, under 15% even better), put a self sealing peel'n'stick membrane (eg Grace Ice & Water Shield) over the roof deck, and put the rigid foam above that. "That said, there really arenât any reports of failures or problems resulting from the use of vapor-impermeable materials â for example, polypropylene, vinyl, or foil-faced polyiso â to make ventilation baffles. Thanks so much for your feedback. If you go ahead with this plan and end up drilling big holes in your roof sheathing, you had better be meticulous when you air seal around the perimeter of each ventilation baffle. Response to Bill Every rafter bay has a 2" by 24" space that runs from the eves to the peak and then is vented out through the space under the metal ridge cap. Seems like a lot of possibility for problems here. Typically, examples of a good air barrier would be interior gypsum drywall -- which only works if it is continuous (it can't be interrupted by purlins or rafters) -- or peel-and-stick (like the Weatherlock product you plan to use). I am trying to avoid extending the rafter tails to support the eaves as the visible roof sandwich gets too thick and heavy looking. You can now walk on the Plywood/OSB as you work since it is glued (thats why glue + Tape rather than just tape) and also supported by the service cavity (via perpendicular framing lumber). It's also possible to use one of the vapor-permeable European air barrier membranes, as long as you are very conscientious about sealing the seams with a high-quality tape. It insulates the chimney pipe and keeps the surface of the outer wall from becoming too hot. super helpful. They will wound plastic wrap around the pipe boxes to hold them together. Response to John W. 200 yr old timber frame Q. And I came across a resource of paper-back 4" poly iso (damaged) for $16 per panel. So, the liner would go inside the flue outlet. But first, it is necessary to clarify the term chimney pipe. Due to the construction, there is almost no chance of getting adequate air intake via soffit vents. I'm thinking this would be "belt and suspenders" should the standing seam have leaks. As with the gas water heater, an electric water heater has a thermostat (4), temperature and pressure relief valve (5), a drain valve (6), the tank is insulated (7), and it has an anode rod (8). From my subject line you can see I have quite the house. Q. But itâs a time-consuming process (I tried it out today), Iâm still working out how to get all of the seams (like at both ends of the rafter bay) air tight, and Iâm wondering whether to just do the OSB boards. I havenât been able to find any information on insulated floors. A. Thank you! I would like to advise my sister on how to insulate there cottage cathedral ceiling , climate zone 6, on Christian Island, Great Georgian Bay, Canada, The cottage is only used from April until October. "Heating isn't that big of a concern but moisture is.". So, take these specifications into account before deciding on a ventilation system. Hi Martin, Thank you once again for your prompt response and detailed explanation of the thermal bridging. For these, customers can choose between flexible or rigid installations. Originally we planned to install R10 rigid above the sheathing (along with another layer of sheathing to support the standing seam panels), but due to dangerous conditions (steep roof, constant rain / wet / slippery) we would prefer to save the budget and skip the additional work on top. Q. The air/moisture barrier on the walls is external (Delta SA) The only way to create a cathedral ceiling with this type of roof is by using an unvented approach. There are 4 recessed lights in the ceiling on the side of the beam that gets the condensation, but there are also lights on the side that is always dry. Response to Jim Boyd I would make sure the rafters between the batts and the foam at a 45 degree angle are blocked off and the foam is completely sealed on all six sides. Or in other words, can you use two impermeable insulation types? Miles, The most common include back-drafting due to negative air pressure in the room. Codes vary, and your local code may well require only R-38 for a cathedral ceiling. I am with Martin on this one, your detail is labor intensive for little if any gain in my opinion. The overall house is *continuously* well ventilated with lots of louvered shuttered openings (No AC). In the section "Can I use dense-packed cellulose as the only insulation for an unvented roof assembly?" I only knew about that from doing research) the sales person told me that I could either live with it or put up a continuous layer of 1" polyiso against the bottom of the rafters, then strapping, then the drywall. Please advise and thank you! An alternative would be to remove the 2â EPS over the cathedral ceiling and put down 4â total of polyiso or XPS (and and additional 2â EPS elsewhere), but it sounds from your posts like polyiso and XPS are not the best choices in cold climates (and for long-term performance). I really hope borate will be enough considering the conditions. Furring strips 1/2" over XPS aligned with rafters held in place by 8" screws into rafters A material like MemBrain (with taped seams) is one possibility. (Interior air can move through small air channels between your rigid foam and thereby reach the underside of the cold sheathing. Chimneys are typically vertical, or as near as possible to vertical, to ensure that the gases flow smoothly, drawing … x 12 in. "Can I use rigid insulation below interior plaster finish to increase R-values? The cathedral ceilings of the 1970s and 1980s were thermal disasters. Some other inexpensive air barrier besides drywall? Lastly, I kow the recessed lighting is horrible, but what can I do if it is already installed? The ceiling joists are 2" by 12", with the addition of 2" by 4"'s to make for a total space of 15" above the drywall. I would think it would be limited. fill 2X6 bays with R-21 fiberglass bats. thanks And should this run continuously down the whole eve soffit of the house? I donât have the option to insulate above the roof deck. Ground snow load here is about 30lb/sq.ft. Your options are described in the article above--you can add venting by installing baffles below the sheathing to hold back the insulation, or you can install at least R-20 of air impermeable insulation.
Thermador Gas Cooktop Igniter Replacement, Mustang For Sale Craigslist Florida, Hamilton Ohio Apartments For Rent, Animal Cell Labeling Worksheet, Book Recycling Center Near Me, Features Of International Money Market, Puppy Surprise 2020,