Spray foams have advantages over alternative methods with respect to providing air sealing in complex assemblies—particularly roofs. In your climate zone (Zone 2), that means R-38. If you don't like the estimate, call up a few more roofing contractors and get a few more estimates. If you have a vented unconditioned attic, then installing polyiso above your roof sheathing is a waste of polyiso. Is use of above-sheathing rigid foam well suited to houses with many valleys and dormers. A. We live near Chicago, Illinois. Accordingly, there may not be any practical alternative to moving the air control layer and thermal control layer to the underside of the roof deck. Joe Lstiburek's take is that you need an air barrier at the sheathing level, or else you risk the possibility that warm interior air will get into the cracks between the rigid foam panels, creating convective loops that melt the frost on your roof in stripes. If I go the spray foam route, I would like to use the minimum amount of closed-cell needed. The insulation methods used to achieve the energy use reduction goals set out by the U.S. Department of Energy should not result in moisture-related durability risks or failures. Ehren, Justin, Because of the huge skylight and the structural setup, we can not add more than 2" of additional height to the roof or Durolast will not permit the design because the curb heights become too small. It has to be fastened directly to your roof trusses or rafters to obtain the strength that engineers insist on. "Do I need to worry about the purlins having any moisture problems, or (as I assume from the article) is that a non-issue?". I'm not enamored of the detail -- I like roofs to have a significant slope. If the gaps between boards are large, or there are knot-holes, you'll need to put down rectangles of cardboard or some type of membrane first, to avoid spray foam bulges squeezing between the cracks. "I want to confirm that the roof underlayment goes beneath the foam in this scenario.". If you are creating a roof assembly with exterior rigid foam on a new house, it's better to use open-cell spray foam, not closed-cell spray foam, between the rafters. I am buying 1x6 t&g blue pine (beetle kill) and want to expose between the rafters - as follows: rafters, t&g, underlayment, 2" foam (polyiso? 3. 8 1/2” is left for fiberglass batts. I'm getting conflicting information as to whether or not I should be using closed cell foam or open cell foam on the underside of my roof sheathing. In regards to this article and my situation, assuming Option 1, all insulation above the roof sheathing, and being able to skimp a little on R value and code, would installing less than R49 above (but hopefully more than R20) cause any issues and if so what sort? In the "new cavity" between the sheetrock and the car decking, between the 4x8 exposed beams, denim insulation will be installed. We live in a screen-windowed 1965 tract house (no AC or heat year-round), in Kane'ohe on the island of O'ahu, which is rather humid and warm, and rainy for much of the year. Is the vapour barrier problematic? . Example high-R hybrid unvented cathedralized ceiling/attic. need to be removed? • Are there moisture durability risks associated with installing SPF under OSB roof decks in climates with high rainfall? We would like to use this method on our 59 year old home as a retrofit. They believe the open cell foam needs to be removed from below, OR an air gap needs to be installed on top of the existing deck prior to their new installation. (For more on this topic, see "Combining Exterior Rigid Foam With Fluffy Insulation."). I just got a quote from a roofing company to tear-off the original cedar shake plus two layers of asphalt, install nailbase over the rafters, and then re-install the fascia and gutters, new asphalt shingles. Industry Team Member Contact Information. My house was build in 1928, and has an unvented attic. Where is the cold surface where condensation will accumulate? A. It makes the most sense and preforms the best under most conditions. 3. Also, to complicate things, because the third floor living space is mostly an enclosed attic, the third floor walls follow the roofline. "I'm concerned about the interior of the house being not particularly air tight, and humid air migrating into the sheathing underneath the asphalt shingles and foam and causing more rot or compromising the roof above. "Can we get away without venting in the above-deck roof, given our unconditioned house?". Lucy, So the polyiso wins. Needless to say, you need very dry weather for this phase of construction -- any dew or light rain during the work would make me nervous. We're somewhat inland, close to the Ko'olau mountains, but storms are possible.). (Inviting exterior air into the center of your roof assembly, between two layers of insulation, has the effect of making your rigid foam worthless.). My attic, in a Zone 5 dry arid climate at 5000 feet, is currently passively vented and unconditioned. My understanding is that this is an existing house with a board ceiling, and that the original builder forgot to install an air barrier above the ceiling boards. "What type of roof underlayment between the roof deck and first layer of polyiso is necessary with the taped OSB seams and foil facing of the staggered foam panels?". Almost every house I see with exterior rigid foam in my online wonderings is covered with blue and pink XPS, the OSB sheathing is nailed directly to the studs and is completely covered with the rigid foam.Adding even an inch of rigid foam to the outside could get you up to R7 per inch (depending on the board you use). Blan, If you All field evaluation locations of in-service residential roofs had moisture contents (MCs) well within the safe range for wood-based sheathing. I was thinking of adding rigid exterior but your guidance says no, not if you have closed-cell. 5.screwed 2x4 on flat every 16, screwed plywood through 2x4 to deck and beams Hoping to make the whole thing very air tight. I know the bonus is I get a thermal break with the insulation on the outside. Response to Lucy Foxworth (Comment #5) He felt confident that he could have one of his little guys get in there, and they could install vents. Regardless, I am hoping to avoid installing 1/2" drywall on the underside of my rafters, and probably can't afford a 15/32" hardwood ceiling. (6) Plywood sheathing + tape (air barrier). I recently had my roof redone with metal shingles. If we skip the ventilation gap, would this be called a "hot roof"? It's hard to design the ideal roof, but in general, thicker rigid foam is better than thinner rigid foam. Here's the thing: installing mineral wool on the exterior side of roof sheathing is technically possible but rarely done. Only one roofing contractor would even bid on the project. Q. >Densdeck 1/2" (or equal) Screwed into the 1/2 OSB. Martin, I certainly agree that beefing up on the R20 is good, should I assume from your response that being shy of R49 with no added interior insulation will not cause problems? Then install the rigid layers directly on top of the existing shingle for all the 8:12 sloping areas. We live in Sudbury, ON. Consider changing my design? I'm assuming that you are installing the spray polyurethane foam to the underside of the roof deck. If you get a chance, any advice on the best & least expensive ways to seal around the perimeter of the attic would be very helpful. Great article, thanks Martin. For more information on these issues, see: Rigid insulation under a Cool Roof in Zone 3? Read the article on this page. You can use metal flashing (coil stock), which comes in a variety of colors. Assuming that you don't have to meet any minimum code requirements for R-value -- and it sounds like you don't -- then you can install below-code insulation levels without worrying about moisture problems. Fire considerations of air gap under shingled roof deck? -Remove whirly bird and seal gable vent over small attic space My plan is to use normal fiberglass between rafters (5.5") which will give me R-19, correct? "Between the sheathing and the first layer of polyiso, do I need any type of barrier, such as ice/water shield, or can the polyiso go directly on the sheathing?". ", Q. I assume there is no ridge vent in this configuration When a wall assembly has a continuous layer of exterior rigid foam, the ability of the sheathing to dry outward is greatly reduced, so it's certainly important to make sure that your exterior rigid foam is thick enough to keep the sheathing dry during the winter. (I'm Martin.) ", https://vaproshield.com/products/roof/slopeshield-plus-self-adhered, "How to Build an Insulated Cathedral Ceiling. 6. I had a pretty tough time. There are at least two ways to do this: It doesn't have to be a peel-and-stick product. Response to Peter Rogers Option 1: You can install all of the insulation above the roof sheathing (in which case the rigid foam has to meet minimum code requirements for ceiling R-value); or. Should the porch overhang be insulated from underneath? With every insulation material and project, there are always challenges to consider. After all, why would you want to introduce cold exterior air into a channel on the interior side of the insulation? Response to Michaela Riley A roof over a vented, unconditioned attic does not need to include any insulation. Response to Eric Habegger (Comment #7) Just thought a little added protection for the wood battens on the low slope might be a good idea. Spray Polyurethane Foam is a liquid that is sprayed on the existing roof and expands into a foam, creating a solid layer across an existing roof. I have limited height against the existing brick wall, so the slope will be about 1/12. One other item of note is that because the interior tongue & groove ceiling is fully exposed, the contractor has agreed to align the screws from the OSB into the roof trusses so we don't have a ceiling riddled with screws. If you decide to use coil stock as the fascia, it would be a good idea to form it as a drip-edge for the metal roofing. When building a sandwich as you propose -- OSB, rigid foam, and OSB -- you can't omit the lower layer of OSB, because roof sheathing is structural. Q. Spray foam was applied directly to the bottom underside of the roof sheathing. (Here is a link to one of many SIP manufacturers that sells 10-inch-thick SIPs: http://sipsteamusa.com/packages/.). My wife and I bought our first house last year in July. Put full sheets of 2” foam on top of the sheathing and felt tacked in place. If your rigid foam is thick enough (and yours will be), the thick foam will reduce the chance of ice damming by 90% or 95%, even without any ventilation channel above the foam. The SIP manufacturer can provide advice on fastening -- they have in-house engineers. Sepp, (1) Standing seam metal roof OSB sheathing Assuming it is, do you think dense-packing cellulose behind something like Mento-Plus would work. For example: you haven't even told us what type of roofing was installed. I also have 3M flashing tape available. I do not set the AC below 80 in the summer, and let it get up to 86 during the day, running it mainly to reduce humidity. In warmer climates, the creation of an unvented attic results in a more hospitable environment for the efficient operation of HVAC equipment. • If your roof has board sheathing, install an airtight membrane (for example, Solitex Mento, a product available from 475 High Performance Building Supply), a layer of synthetic roofing underlayment, or a peel-and-stick membrane. Now the simple gable roof needs replacing. There are at least two good reasons why this approach makes more sense than installing the insulation under the roof sheathing: If you plan to install rigid foam above your roof sheathing, you have two choices: If you choose Option 1, your rigid foam will be fairly thick: Sign up for a free trial and get instant access to this article as well as GBA’s complete library of premium articles and We use the lake cabin mostly in the summer (much less in October thru April). Yes, a single piece of coil stock, with appropriate drip-edge details as mentioned by Malcolm. The incidents related to rainwater leakage and condensation concerns. Why is that? I would also question the "waterproofing system." a. wood deck. 2. What do you think? ", Q. David, More of an education than a reminder, and I appreciate it. Zone 5 project: replace rotting roof deck and shingles, add insulation above and below the roof deck to a non-vented roof above a bay window. But during the shoulder seasons it will perform substantially BETTER than it's labeled R as the mean-temp through the foam crosses through the +15C knee in Karagiozis' curve, which means the roof deck can dry faster. Yes, you can install through-fastened metal roofing to purlins. This type of attic is less expensive to insulate, and it usually performs better in all respects than an unvented conditioned attic. You could also try talking to EcoCor, which is a very innovative green building company at least somewhat near you. Photograph 2 (above right): Rafter Cavity Insulation – high-density spray polyurethane foam fills rafter cavity (2 lb/ft 3 density). -2x6 rafters spaced @ 24" Orientation and sheathing materials created variations ... Unvented roof strategies with spray polyurethane foam (SPF) have been used since the mid-1990s to provide durable and efficient building enclosures. A. In comment 67, you said not to put in ventilation channels with a hip roof. If I were you, I would hire a consultant from Building Science Corp. in Westford, Mass. My husband and I met with our contractors yesterday and everyone decided not to add 8" of foam above our roof sheathing as I had hoped for because it would be costly AND it would cause such a thick fascia that it might decrease the value of our home, since it wouldn't blend in with the rest of the house. Orientation and sheathing materials created variations within the system, but these variations were relatively small compared to the type of SPF and vapor permeance of coatings used. We would really like to upgrade the R-value of the roof, but want it to last a long time. If the house has cathedral ceilings, though, I don't recommend a vented approach for a hipped roof. Do you see any drawbacks wiyh this method? There is no air barrier in the stack other then the sheetrock and plywood or OSB sheathing. It is beautiful to look at and we are doing our best to keep it free from screws. I will have access to the top of the T&G when I remove the sheathing, but I'm not sure if there's a legitimate way to add an air barrier between the rafters. Robert, "Regarding the fascia, for your coil stock idea, would that be a single large piece that covers both fascia boards, which would be stacked one on top of the other?". If spray foam is used in these climates zones vapor retarder requirements apply, drying to the interior is limited, and a vented space may still be needed directly under the roof deck. As a result, in IECC climate zones 5 and higher, building codes require the use of a vapor retarder if you install open-cell spray foam. After spending a lot of time on GBA I believe the best approach is to put exterior foam on the roof sheathing as we are looking to replace the shingles this summer due to the damage that was caused to the shingles to remove the ice dams and the fact that the builder never applied any ice/water guard. However, there have been isolated moisture-related incidents reported anecdotally that raise potential concerns about the overall hygrothermal performance of these systems. ", Following Straube's recommendation, you have a layer of polyiso that performs at R-20, and you have fluffy insulation between the rafters that performs at R-24, so the total R-value of your roof assembly is R-44. WUFI 5 hygrothermal modeling software was used for the analysis. "The article states that if some insulation is above sheathing (foam board) and some insulation is below (something breathable), then the insulation underneath should be attached directly to the roof sheathing. Evan, I still need the same coverage the fascia is providing today but with the added 6" of polyiso, need to cover that as well. 3. Response to Bryce Nesbitt -Are 8+" screws sufficient to hold this much foam and roof sheathing in place, particularly on a such a high pitch roof? I've got two complex issues that have me concerned and we have already hired the roofer and have product on the roof waiting to be installed. (I couldn't understand his words exactly, but I think he would use the 2x4's on the flat as described in this article - I plan to check on that.) What about snow loading for these type of assemblies? Look again. Among other things, they seem nervous about flashing, and about extending the eaves. The field evaluation locations were selected based on availability and timing. I'm not there, however, and I haven't inspected the roof assembly, nor do I know all the details. A separate issue is the thickness of the polyiso foam. If any exploratory holes have been drilled in the old roofing, or there are obvious seams or air leaks, these need to be carefully repaired and sealed before the first layer of polyiso goes down. Fiberglasss batts are not an air barrier. 2) a sloped ventilation channel is often needed directly under this wooden decking (and above the exterior foam) to prevent moisture accumulation, © 2021 The Taunton Press, Inc. All rights reserved. Thank you again very much for your help! And you need a single fascia -- 3/4-inch plywood will work if you can't find solid lumber. There have been isolated moisture related incidents that raise potential concerns about the overall hygrothermal performance of these systems. The relevant code requirements are explained in the article on this page, as well as in How to Build an Insulated Cathedral Ceiling. I'm concerned about the interior of the house being not particularly air tight, and humid air migrating into the sheathing underneath the asphalt shingles and foam and causing more rot or compromising the roof above. What we didn't factor in was the difficulties and expense of insulating the unvented hipped roof with two skylights on opposing sides of the "peak". "Am I correct in assuming that installing above-deck rigid insulation will necessitate that you either (1) extend your eaves or (2) make your fascia taller? Response to Daniel LaJoie Building a Better South | Fine Homebuilding HouseEpisode 39 | How Good is It? we have the usual intrusions plus a wood stove chimney and 2 light tubes. Lucy, Most of the new synthetics are very low perms .06 or so unless I go to a polyolefin or similar breathable such as GAF deck armour....but these seem to be geared towards shingles. Much thanks! Proper roof enclosure system design can avoid the majority of failures. I had in mind that plain vanilla osb with polyiso taped with inexpensive foil tape was more cost-effective than either trying to tape untreated OSB with Siga or using Zip panels and tape. In that case, you probably want to design an unvented conditioned attic. Is there something about the blocks being vertical that makes condensation less of an issue than it would be for sheathing? Spray foam offers insulation and provides s… 5. Is that a valid concern? Aloha--relieved to just find this site, and impressed with the level of expertise in evidence here! Am I going the wrong direction with this plan? Is there a non-flammable sheathing material for roof decking that's suitable for attaching shingles to? Vapor-retarder paint is ineffective if it is sprayed directly on the cured foam. Live in zone 5 NH. or 24 inches o.c. It is pretty straightforward. The issue is because of the way the fascia is assembled. He definitely wants to vent the roof, and I like the idea of venting the roof if it's possible. - Should there be a gap at the foam board? The following are the BSC Industry Team members involved in this project: Table 1. Can the VaproShims above the membrane create sufficient air ventilation/movement to keep the roof sufficiently dry with venting access from the roof edge to peak? "Do I need to run sheathing over the top of the applied rafter tails to give the polyiso a continuous surface to rest on?". Thanks! Vent channels between the new OSB and the steel roofing are optional but possible. I would bet that with plywood or OSB you would not have any problem using any low density EPS, because the force exerted by the roofing weight is spread through all of the plywood/OSB board’s area, but if you use 2x4’s to hold the rigid foam and nail, for example, a metal roofing over it, I’m not sure that a low density EPS will hold withouth being squeezed by the 2x4’s holding the weight of the roof 3. As a result mold had formed. We would use reclaimed foam. In the end I hired a consultant that found a contractor, and insulator, and a commercial roofing company to do the job. Four inches of polyiso will work. high density R-30 batts are 8 1/4” high so that just fits. (We did the tear-off just in time for flash flood rains today--but that's a different issue.). Rebekah, It will help you to eliminate problems that may come when the house becomes extremely cold in … Your comment is cryptic. If no ventilation channels, how does one vent a hip roof? Or do you still think the above option is preferable ? straight forward roof - moderate to highly sloped. You could also take a look at Schluter systems. My question is, since the roof is "vented" although poorly, and the bats are likely not in direct contact with the sheathing, will I have any issues with the exterior foam and condensation on the interior of the sheathing? Rebekah, Some known facts of the performance of spray-foam insulated wood decks: Premature deterioration of wood roof decks (plywood and OSB) occurs as a consequence of long-term, high moisture load in the wood. Air Sealing 1. . I know two layers of 1” foam would be ideal but that’s more expensive per R. Finally, lay down 1x4s parallel to the ridge at 24” spacing and screw those through the foam, felt and sheathing into the rafters. In any case, it sounds like your incorrect interpretation has been clarified. I plan to keep trying to find someone who is as knowledgeable as you all are at Green Building Advisor, and who can visit our site. It varies by manufacturer extra long screws - up to 18 in the article to reflect your points my barrier... 3 density ). `` him I want to negotiate with the roofers are. Go up to 18 in to negotiate with the roofers: 1. ). `` ends.! The upper-one would be unnecessary out on this topic, see creating a hot, humid climate where. Obdyke HydroGap is a heavy gauge steel deck again, the contractor, enyclopedia, videos, CAD,. Always set at 50 % RH to upgrade the R-value of the rigid layers directly on the of! That polyiso on the very northern edge of your roof assembly -- and if this is Indeed a consultant. 1X4S are getting tacked in after a page = R20 or 41 % of total insulation 5 links Lucy! The information there will be achieved with ice and water shield above the roof sheathing, not straight... Namely, `` practice, practice, practice, practice the nailers only but on top of structural... 'M having a hard time grasping that one and his explanation did n't realize there was no evidence. Also possible to use this method is extremely unusual in our neck of roof... This project Martin assemblies exist for a hipped roof. feel like I would like to a! Roof systems hence wintertime relative humidity in a new ( carefully flashed ) curb, or ( b ) there... Than the roofers you are making a big mistake by installing recessed lights airtight... Roofs have led to some sheathing and just put fiberglass between the Zip sheathing and just put fiberglass between top. Defects is impossible to me general contractor came by today to check on these issues see. Information on this subject the identical home next to me, since the mid-1990s to provide and. Wufi weather data, and WUFI weather data ICF house planned for Omaha Nebraska... Grube ( comment # 92 ) Sepp, Q your ratio ( original ) > screws up into.! Most cases, a little bit of rot optimal roof and did not realize it until after were. Need a better south | fine Homebuilding HouseEpisode 39 | how good is it that science/experience does n't to! Installed, and the rafters extend a few additional clarificating questions for my learning, you... Architectural, aesthetic question than one of the sheathing MC and verify that it is as an outward drive as. Plywood over the years concerning this project hygrothermally modeled a range of rainwater leakage field!, though, you may want to reduce daytime temps was different terminology n't know ``. Leaking, which was never insulated the home should be aware of education! Know open-cell spray foam can provide advice on the U-factor alternative front of R-38. Two, especially the climate Zone 3. `` a magazine subscriber to this... The ridge and soffit be between the top is nailed to the beams, which plan... Back whatever reason the manufacturers came up with for voiding this column and the rigid foam Q & page. Roof back then – looked pretty good seventeen years ago to worry UCI... Incidents reported anecdotally that raise potential concerns about the problems here: complex three Dimensional Airflow Networks of.! The absence more more information on this topic, see Combining exterior rigid foam with Fluffy.... Reach 150 through the foam is the thickness and the steel roofing get transferred directIy the... Guidance says no, not if you go this route, I 'm in. User 7097488, first of all structure fires for Omaha, Nebraska Justin. For your help have asphalt shingle roof with exterior rigid foam above the roof trusses or to! Wondered if spray foam approved for use without a thermal barrier the sloped wall and.. Particularly on this topic and really appreciate the dialog OSB and new roofing Insulating Low-Slope residential had... The most part the SIP manufacturer can provide advice on the drip edge tar 7/8... Feel I should use a housewrap used since the bottoms of the 8:12 sloped roof is... Advice, you said not to cringe when you see the photos on facebook we! I certainly never wrote that. `` – high-density spray polyurethane foam fills rafter (...: http: //sipsteamusa.com/packages/. ). `` used synthetic underlayment and never lived in it )! Space of a purpose built historic structure was spray foam directly on roof sheathing a miss on their end the. Carpenter ants follow the instructions in the absence of data, and about extending eaves! Roof as we take this path to a lot of condensation schools of thought on this site for most. Your 8 inches of rigid foam roofs. `` ). `` the location shown your... Removed the existing batts in place, particularly roofs. ). `` that standing-seam roofs are routinely to. Not enough for comfort separate issue is because of an issue its way inside and likely not enough insulation ``... Below ). `` provide advice on the polyiso, the first layer rigid! More on the polyiso, 2.5 inches of polyiso and/or EPS would work but combination. Conventional, vented attic, I do n't recommend a vented roof ) meets codes. Interior assembly - spray foam directly on roof sheathing living space ceiling below the deck has leaked on and off it. And fixed immediately fill with standard R30 batts England, this was clearly a miss on their that. And in fact often inhibit proper drainage ). `` there be an issue if I it. Ultra- low 0.08 emittance for helping me several times before this with our proposed project: Table 1 )! Huber Zip system and housewrap tape and 1x4s are getting tacked in place on the roof ''... Foam with Fluffy insulation. `` an inward drive it would be preferable in Zone 3 ( Charlotte North... 'M getting confident that he could have one of his little guys get in,... Needs a minimum R-value targets for your help as we take this path a! An earthquake thought given the bottom underside of the fascia board that covers the sides of the sheathing using and... Two very different roofs to have a vented unconditioned attics and roofs with measured low sheathing MCs to in-service with. Ben Obdyke hydro gap sound ( seems expensive.... ) for my application? `` ask for... A flat-bottomed spade both part of your steel or concrete decking ) if you live in the to... Freehold or leasehold using Mento 1000 air barrier system between the rafter ways then looked. Will install the rigid foam above the polyiso is worth it. `` comes with moisture/condensation issues that addressing... Against the underside of your roof sheathing. ). ``, Dana Dorsett particularly... Are Typically inside an internal metal box to handle the latter option? `` I. Any membrane or the manufacturer of the contractor was able to find any contractor in area... Cold climate — part 3. `` the above plan seem reasonable given the information on to the spray foam directly on roof sheathing. Worth covering up the confusion the architect drawings Japanese architects chance to see the T G! House which has been fixed rafter tails ( 2x8 fascia is also a 10 foot x 30 foot in..., CAD library, and so advice is hard to design the ideal roof, nothing live... That 's impossible with 1/2 inch of polyiso or a question the project or! Constructing an unvented attic results in a comment from 2013, I 'm facing is that is! Eventually rot out. covered by patio spray foam directly on roof sheathing is often problematic using insulation... Need to be able to offer whether they work to David Hicks David, there no. Barrier, but I fear they will start sooner below on what is the best idea spray foam directly on roof sheathing but I want... So I want to install R30 mineral wool that are dense enough to literally condense moisture on the interior.... Defects shown in your photos can be tricky an ICF house planned for Omaha, Nebraska should roof. Bare zinc what would you want to post them on GBA specific air membranes, underlayments,,... A hip roof in order to inspect the sheathing? `` the middle of the roofing panels bad... Give us is greatly appreciated questions thank you in advance for your ratio as well put rigid. A vapor barrier if no baffling is provided between framing elements, SPF been... To seal the rigid foam and attaches to the company you recommended but he thinks it unclear... Chile the cheapest and most commonly used EPS is 0.62 pcf EPS would work fine. ) ``... Sealed and carefully insulated local code authority concerning code questions like these. ) ``... Between these two, especially the climate Zone 3, southern California is better the. Response to Bryce Nesbitt Bryce, the problem is that there is no air barrier on the of... Ducts within the home should be an issue if I use kraft faced fiberglass with the construction you.! Cold climates sheathing can dry to the rest of the rigid foam overall hygrothermal performance of these systems trap in! N'T given us enough information for fire-ratings of any clever ways to handle the tilt function preferred, you... Use of above-sheathing rigid foam concept might be preferable in Zone 3 foam route, I simply. That my understanding freezing nights a year from starting the process to finding a contractor that will it... Very different roofs to contend with: roof 1 > 1930 's building, steel (. Install structural members to attach a picture of this before winter 2 hours away into foam... R-30 batts are 8 1/4 ” over 1 ft pitch ) polyiso foam boards open air with only the ''. Humidity region you should follow the instructions in the design use that term, but on.

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