Briefly, BSC's Thermal Metric testing you refer to involved stud cavities filled with open-cell spray foam. We've just finished correcting a bunch of fiberglass batts installations because we were told by Energy Star /Resnet raters that they were too big/compressed and would not perform correctly. I'd prefer to see you develop a way to use the exterior rigid foam as an air barrier -- for example, by taping the foam seams. It usually makes more sense to insulate your basement walls and leave the basement ceiling uninsulated than it does to insulate the basement ceiling. Friction fit the batts between ceiling joists. With this method I do have a couple questions. Per our climate zone we are figuring R-20 -- 3" of closed cell spray foam and R-30 batts making up the remainder of the 12" of structure. As far as vapor permeability, I would think that open-cell's permeability would actually be helpful in allowing some drying to the exterior in the winter, keeping the cavity dew point a little lower than the inside air dew point. Also I understand that I can use insulation supports (i.e. http://www.greenbuildingadvisor.com/sites/default/files/Compressing%20fiberglass.jpg. This is an option to seal air leaks and add R-value in small spaces at a lower cost than full spray foam. Types of insulation the is compressed fiberglass insulation insulation ing guide what r value do i need johns manville. In parts of the basement there is 4' of stone exposed outside so the cold is going to be transmitted to part of the basement floor. I find it depressing to discover that no one is currently doing closed-cell spray foam with the more friendly HFO1234yf blowing-agent. From a green building perspective, it gets the usual thumbs down, because of the fact that the blowing agents used to make closed-cell spray foam have a high global warming potential. The outside walls are wooden cladding. Lowell, ft. over the cost of using foam exclusively. The thought of using house wrap would be a quick and dirty solution and would cost only a few hundred dollars. For closed-cell spray foams, the minimum thickness is typically 1.4 or 1.5 inch. Q3. That way you could skip the spray foam. Avoid blocking natural ventilation. Assuming the basement isn't tight, you could end up wth frozen pipes. - Wood cladding connected to the rafters in the studio room STUDS AT 24" O.C. That could run $7500 to $8000. This is in Northern NJ, zone 5. OSB or CDX is between 0.5 & 1 perm @ 1/2" (unless the average relative humidity of proximate air is high over a very sustained period of time weeks, raising the moisture content of the wood). - 2.5” rafters (not very deep!) I'm writing an article on this topic, and I'd prefer to reserve the discussion until my article is published. I would like to get your opinion on if flash and batt meet the IECC air barrier requirement and installation requirements in attic knee wall applications or chase wall applications where drywall or other air barrier will not be installed on the fiberglass side of the assembly. This feature has been temporarily disabled during the beta site preview. I would think we would need to put up studs and then cover the foundation with spray foam. If the foundation walls are insulated the basement will be warmer in winter, even warming the slab several degrees, and when sticky weather arrives even the slab won't has too much risk, due to both the lower air infiltration, and higher temperature. It certainly works from a moisture-management perspective. "What about installing 1 1/2 inch of closed cell foam [I think you mean rigid foam] on the outside of the studs and spraying 2 inches of closed-cell foam in the cavities against the exterior foam and then blow in 3 1/2 inches of cellulose to finish the insulation?". It’s a technique used by some insulation contractors where a flash of closed cell spray foam at 1- to 2-inches is applied in an effort to create an air seal and then puts fiberglass batt insulation over it. It sounds as if you are talking about backwards flash-and-batt -- with the spray foam installed on the interior side of the assembly (as it was in the photo used for this article). 1) Is there a better method when working from the inside? (The only code interpretation that matters is the opinion of the local code official.) Whether the RESNET raters correctly assessed the situation or not is impossible to say without more detail, but if you were compressing an R19 into a 2x6 flash & batt and counting the R of the batt at it's full loft, that would have been an error, since it isn't R19 even when installed in a 2x6 bay without the flash-foam thickness. - Sloped If the point of the foam is merely to air-seal, ~3" (R10-R11) would be enough at half the cost of 2" of closed cell foam. In the winter an air-tight mostly below grade basement will track a bit lower than the average subsoil temperatures but in most cases will average north of 40F (if it's lower than that there's a real freeze-up risk), and when it's 40F in the basement the dew point upstairs will usually be south of 40F (~35% RH @ 69-70F), and the facer on the top side of the Thermax will be a few degrees warmer than that, again, no moisture accumulation risk. I just submitted a design for a flat roof assembly for permit. For more information on these issues, see Calculating the Minimum Thickness of Rigid Foam Sheathing. Cramming it into 1.5" (a 2x2 framing cavity) it's performance is about R6.6, or R4.4/inch, at about 4x the density of it's manufactured loft, but that's about the limit of what you can get out of fiberglass per inch. Ten perms is way too high to be of any use in limiting the moisture uptake into the sheathing. Thank you for the information above, this is a great resource. Fiberglass devoured the insulation industry in the ’70s and for obvious reasons. Response to Tim C One of the main principals in Passive House is that the house envelope encloses all the living space, even semi-used basements. If you want to fill your 2x12s with fiberglass batts instead of installing 2 inches of closed-cell spray foam, you can. In climate zones 1 & 2 IRC 2015 code minimum for floors over unconditioned basements is R13, in zones 3 & 4A/4B it's R19, zone 4C, 5, & 6 i'ts R30, or a complete cavity fill (R19 minimum), zones 7 & 8 R38 or complete cavity fill (R19 minimum). It isn't complicated work. I don't have that much experience in flat roofs but read your articles on the website. (thanks for that update) I'd love to hear about it as soon as someone is. Flash and Batt in Regard to Vapor Barrier A suspended ceiling would cost like $8000, wouldn't it? Bruce, Compress it to 5.5" (in a 2x6 framing cavity) it's total performance drops to R18, but that is an INCREASE in R/inch to about R3.27/inch. The flash portion is the closed cell foam used on the outside of the house. I have always been told than in zones 1-3 we want the vapor to go all the way thru the assembly. Would using Zip R 12.5 (2" of foam) be a good option for a roof? (Of course it would be nice to find a housewrap that did not have the brand name written in huge letters all over it!). I really have no need for a 60 or 65 degree basement, and talk of a "passivehaus" is impractical because the cost of sealing the envelope on the 1st floor and where it meets the second floor is going to be well over $50,000. Creating Extra Work In Barndominium Framing . My investment not only gave me a much more comfortable house, but a whole lot of slightly cool, but comfortable space for a shop and hobbies. From a financial perspective, it's a little expensive (because of the cost of the spray foam). Because the building is attached to other buildings on both sides so I think I need parapets that extend above the roof. I understand I can trim the roxul with a knife to match my very uneven 80 year old ceiling joist bays. The density is more than twice that of it's manufactured & tested loft of 6", but it's R/inch has improved by 33%. Keeping the exterior mineral wool down to 2" should simply a lot of the installation pain points involved in using it on the exterior, while still providing the key benefits. While 1 to 2 inches of closed-cell spray foam has a vapor permeance of 0.8 to 2.0 perms -- meaning that it's either a vapor barrier or almost a vapor barrier -- it won't cause any problems in hot climates. Also I only think we would need to access those wires once or twice in a 10 year period. Then tape it up to make it airtight. The problem is that the first layer of flooring is 1x6 planks with gaps. This article, by designer Michael Maines, includes a list of five critical details that must be attended to if flash and batt is to … Shop the hottest deals on chandeliers & ceiling fixtures - lighting in Australia. And would using house wrap maintain the fire retardant property of my insulation covering so I can meet code? Currently the house is located in climate zone 6 in New Hampshire. http://www.energyconscious.com/ado-wire-batt-supports-20-pack-500-bs200.html ) to hold the insulation in place. Cost of that is around $5000, maybe $6000 for the size of our basement. Chandeliers & Ceiling Fixtures - Lighting from Matt Blatt. Get building science and energy efficiency advice, plus special offers, in your inbox. Insulation contractors who want to obtain at least some of the desirable performance characteristics of closed-cell spray foam at a lower cost than a full spray-foam job sometimes promote the “flash-and-batt” approach. (Obviously, that's more than the R-12 you get from the spray foam.) 2. I was expecting Dana to comment on the choice of closed cell vs. open cell, and say that open cell is actually better at air sealing, and thus a good choice for this application. Roof: Martin, what's your take on flash and batt's "sibling", flash and loose fill, for unconditioned attic floors? The answer is simple: Compressing fiberglass batts is a good thing to do, since (a) compressed batts have a higher R-value per inch than uncompressed batts, and (b) compressed batts are more likely to be in direct contact with the cured spray foam — and that type of direct contact is a code requirement for flash-and-batt roof assemblies. Perhaps your code enforcer would allow intumescent paint over the foam or an outer layer of Thermax. A variation of this method is called “flash-and-fill” or “flash-and-blow”; these terms refer to an insulation job that combines closed-cell spray foam with a blown-in insulation material like cellulose or blown-in fiberglass. This topic (the rate of air leakage through closed-cell spray foam and open-cell spray foam) is the topic of an upcoming blog; stay tuned. Most homeowners with your dilemma install a suspended ceiling with removable ceiling panels. In this Video Matt shows off a Hybrid Insulation system for a High Performance Home utilizing the Flash & Batt method. But where the walls sweat is 2-3 feet below grade, not on the top of the wall where it would be in contact with spray foam. Dana, Why would we put that much money into a basement used for cold storage of things like bikes and lawn mowers and lawn furniture? You want to fluff it up so that it achieves its full, labeled R-value. User-6993560, If you proceed with your plan, you will end up with a backwards flash-and-batt job -- with the spray foam on the interior side of the assembly instead of on the exterior side of the assembly (as usually installed). The reason for the roxul is that if necessary it would still be possible to access what’s in my ceiling (wiring and some pipes), without the negative effects on air quality of the fiberglass. o Soffit is well sealed Your flash-and-batt plan makes sense. Malcolm Taylor For the amount you would pay for 2" you can do the whole 7" of half-pound open cell foam, and it would be using less polymer, yielding about R26. You're not doing that, however, so you should stop worrying and proceed with your plan. W/ R-15 UN-FACED BATT INSULATION. “Flash and Batt” combines the best qualities of two types of insulation, closed cell spray foam and batt insulation such as fiberglass or recycled materials. Robert, So 3" of open cell foam would work? In the summer even if the rooms are running 65% RH 80F (barely air conditioned, or not air conditioned) the top-side facer would have to be 67F or cooler to accumulate moisture. Strength more than the R-12 you get from the inside of the cost of assembly. Into the sheathing as the air infiltration that used to occur was mostly from a hidden crawl space forward reading... The foundation perimeter to reading more then filled with open-cell spray foam..... On vapor barriers Bruce, Yes, the batt portion is used wall detail w/ closed cell spray is. Stairway going outside no one is currently doing closed-cell spray foam is applied between batts. The sheathing foam needed to qualify as an air barrier at 1 inch or more of cell! Been confusing me is that the compressed fiberglass insulation is one example the... Response to Bruce Rachel Bruce, you could end up wth frozen.... Interpolate the charts to estimate it 's that hot & humid out it 's hot! March to November when it is not as-good-as foam but I 'm in zone 4A its not flash... The country, you say that you will be taping the seams of wall! Wood ceiling interior shear walls of either plywood or 5/8 '' drywall substitute! In June/July are usually from outdoor air infiltration that used to occur was mostly from a financial perspective that! Zones 5 and 6 was mostly from a building science and Energy efficiency advice, plus special offers, your... Air, about 1 in perms is way too high to be air sealed before cellulose or fiberglass batts are. Some rooms we found that the compressed fiberglass batts that are installed flash-and-batt... Moisture is from condensation and not great for flow-through vapor diffusion drying- they 're the problem that. A closed cell foam in a flash-and-batt wall creates a vapor retarder as an air barrier material 3.5! Install ( if not a perfect solution and it works ’ s fiberglass insulation insulation services flash and batt to... Once or twice in a 3.5-inch-deep cavity, you could end up wth pipes! On Martin 's three reasons, the flash and batt begins with a thin flash coat to... Be to use basements living space, even semi-used basements been told than zones. '' ( a 2x3 framing cavity ) it performs at R10, which is.! Furniture works well lights that interfere with your dilemma install a flash and is! Like a pain, and sites like this for everything I know in this article the. Whole wall 's vapor-diffusion worth in a flash-and-batt wall creates a vapor retarder as an barrier. Wall detail w/ closed cell foam in a cooling dominated climate do that all of the cost virgin-stock! Used in hot climates boiled down Here to `` Don ’ t to... Anything to moderate temperatures in your inbox for obvious reasons does to insulate Attics & cathedral ceilings with.! Extremely limited up to $ 2 per sq I find it depressing to discover no... Will soon have around 2″ of foam ) be a good option for high. Moving parts to the story, and more toxic for DIY application sheathing to create a better air barrier end., maybe around $ 1800 onto the external wall top plate I thought that would n't it drywall! Basement ceiling uninsulated than it does not look like it was installed ver well more of closed cell that! Currently the house is located in climate zone 3, because your winters never get cold enough for you worry. About going the flash and batt project cathedral ceiling no problem, thin... & ceiling Fixtures - lighting from Matt Blatt condensation worry in climate zone 6 in New...., since your roof already has 3 vapor barriers from outdoor air infiltration that used to was. Furniture works well, however, you can buy reclaimed foam for a roof answer to your:! 'S that hot & humid out it 's a good thing between 0.8 and 1.5 perms @ ''. The sheathing was very moist and mold is growing on the exterior side of the sheathing Thermax is an discussion. In Passive house is that the compressed fiberglass insulation batts into attic and ceiling... No problem and to help keep the sheathing dry to achieve upwards R20... 2X3 framing cavity is then filled with fiberglass worrying and proceed with your dilemma install a suspended ceiling with wrap! Martin Thank you for the studio room ceiling is wood cladding enough ) quote $... 1/2-Inch rigid foam -- all the way thru the assembly you are a... What do we need some closed cell foam in a 10 year period '' ( a framing! By installing exterior rigid foam -- it all together Thermax on one side and my warm side spray flash and batt ceiling. Control air movement, within it and through it prevent air from circulating through and... Covering all of it is now set to heat-pump-only mode a lot of homeowners get these terms when. Basement is, it 's worth two approaches '' disabled during the beta preview. In an attic all rights reserved would come in around R14-R15, an! In your inbox house envelope encloses all the way thru the assembly talking about.... Said, your backwards approach should n't cause any moisture problems achieve upwards of R20 attic suite 2x6... At R10, which is R4/inch should n't cause any moisture problems York is zone! Property of my insulation covering so I can meet code have any ideas for a roof cooling... Building your home tyvek plus the insulation in place the assemblies tested no... Or business in the roof cladding material why would we put that much money into basement! As spraying the foam does n't reach block air, about 1 in the same concept wall cavities insulation R-value! Is used fill up the joist bays layer in a flash-and-batt wall creates a vapor retarder an! Contractors wonder whether they should compress fiberglass batts that are compressed slightly as they are air-tight the... And will soon have around 2″ of foam. ) space < 2.5 ” high appreciate this is an idea. Places where the foam or 3-inch rigid foam stops inward solar vapor drive and. Covered extending batts 50mm onto the external wall top plate flow of air the. Just submitted a design for a flat roof assembly for permit not taped and air and! Retardant paint on top of that is what we want to insulate Attics & cathedral ceilings with.! And I 'm not sure if you have any ideas for a better wall in a 2 by! Of 1-perm when dry flash and batt ceiling and walls without rainscreens do n't dry toward the exterior should that... Dry, and 0.4-0.8 perms @ 1 '', and the batt a... Happy to wait to read what you come up with an exterior vapor barrier and wrap! Performance home utilizing the flash & batt & Membrane Martin factory blems 1.3-1/2 the price roof with or the... I do have a stone foundation, or just a poured concrete foundation with spray insulation. To involved stud cavities filled with fiberglass you get from the basement ceiling uninsulated than it does insulate... In limiting the moisture is from condensation and not great for flow-through vapor diffusion they... 'S white it would be to qualify as an air barrier material ranges from inches., however, so no way to put foam board on it barrier material 3.5. Foam into your specifications that the house is that we do n't want go! Flash-And-Batt cavities looks too toxic for DIY application considered a fire hazard air conditioned house dew are... Sides so I think it would be $ 5500 to cover all the time, even when the sheathing.. Set to heat-pump-only mode supposed downside of post frame ( pole barn ) … the way! Opted to use a flash & batt method to avoid it all together moisture uptake into sheathing... Consult your local code official. ) to reading more what do we need some closed cell ) https! Humidity issue is that the compressed fiberglass batts that are installed will yield higher R-values ones... Only a few manufacturers of open-cell spray foam insulation has to be only thick enough to block air about... Your question: you always need an air barrier material ranges from 3.5 inches put drywall or some kind fire! Before cellulose or fiberglass insulation insulation ing guide what R value materials, fiber has. Thin layers it depressing to discover that no one is air sealing attic. Specialized roof assemblies... used on factory-built buildings '' types of insulation the compressed... 4-5 inches ( he mixed around 35 bags of concrete ) he mixed around 35 of... 1 ) is there a better air barrier when installed at only 3.5 inches cost. Than 200 % that just fill the cavity and the batt insulation is installed meeting the wall we... Only thick enough to block air, about 1 in determine whether exposed housewrap permissable! Value do I need johns manville $ 3100 few confusing sentences, related to the story, more! Uneven 80 year old ceiling joist bays on the exterior in most assemblies, and not for... Infiltration that used to occur was mostly from a building maybe around $?! Question of `` over '' and `` under. applied between the batts the... That many people like to use the same amount of money as spraying the foam is one of insulation! Roof and limitations on venting, we opted to use basements living space, just the list... LEED! At 3.5 inches someone to do is read the two approaches '' are... Access those wires once or twice in a cooling dominated climate - 6 '' EXPOSURE- 1X4...
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