Fiberglass insulation retains moisture, which can lead to mold and mildew issues in the walls. As I think on it more, would Frank's proposal in effect create a very deep cathedral ceiling -- where the structure begins w/sheetrock on interior ceiling and ends w/roof covering (such as in a hypothetical structure that uses say 48" deep rafters)? In our ongoing efforts to educate homeowners, we have put together this article to explain what flash and batt is, as well as how it works and the pros and cons. Find batt insulation at Lowe's today. A new build home shifts and settles, because closed cell is a rigid foam material it won’t move with your home. The answers to many of your questions can be found in these two articles: How to Build an Insulated Cathedral Ceiling, Q. Fiberglass Batts or Glass Mineral Wool Metal Roof Insulation. The code needs to be updated and have the proper words added. Throughout her career as a journalist, she has won several awards from the The Society of Professional Journalists - Detroit Chapter and the Michigan Press Association. Sprayed-Foam and Foamed-in-Place Insulation – Liquid foam insulation is sprayed where it is needed, then hardens into an effective insulation material. I have toured a house of his in Lake Placid during a cold winter day with a window open. Fiberglass batt & roll insulation options are common because they’re so easy to install. Or is this a case where 2 plus 2 equals 3? Kent, (8-Bags) (26) Model# 690989 $ 634 88 /pallet. The contractor adds the fiberglass just to hit the prescriptive code and in an attempt to cut costs. You write (in direct contact) and the code states DiRECTLY UNDER. “The air impermeable insulation shall be applied in direct contact with the underside of the structural roof sheathing as specified in Table R806.5…. And a Bruce Brownell home is a PGH. Heating the attic takes care of the ceiling but you have relatively rapid heat loss to the exterior due to the 5 rating of the roof. If so, then it would seem he has met the R-38 requirement. spray foam insulation problems | Would the resulting air gap between the insulation and sheathing or drywall add, reduce, or have no impact on the R rating (understanding the thicker wood gives me a little more R)? Flash and batt uses closed cell spray foam insulation as an air barrier, and then a fiberglass batt or blown in fiberglass or cellulose insulation is installed over the top of the spray foam insulation. x 48 in. The performance method helps meet code for insulation materials like foam that creates a total air seal in the home. Peter, you straight out state exactly what the code does NOT state. It typically has 3 variations: bare foam board, one sided sheathing … This hybrid method could work if it was installed properly, but many contractors who recommend this install less than the required 2-inches of closed cell to create an air seal. So would convection airflow and other leakage in Frank's design be an issue or would having insulation against both sides reduce the temp differential enough to eliminate the problem? And someone has to go thru all the details that do not work and get them out of the system. You’ve come to the point in building or remodeling your home where you need insulation and your contractor is recommending flash and batt for your walls. But his plan contains a twist: He wants to spray the underside of the roof deck with foam and install the batts between the joists at ceiling level. Shop batt insulation and a variety of building supplies products online at Lowes.com. Flash and batt is spray foam insulation with fiberglass batts. Now that you have read all about flash and batt insulation, you may be deciding it isn’t the best option for your home. Both are … The code also allows for air-permeable insulation, such as fiberglass or cellulose, to be used under the roof deck as long as rigid foam is used above the roof sheathing. You feel confident in your insulation knowledge, but you aren’t really sure exactly what flash and batt is or how it works. To ensure full coverage and reduce spillage use insulation … The correct R-values certainly changes things. The warm air and cold air will meet in the cavity creating condensation. If you create an air seal with 2-inches of closed cell, you don’t need the added fiberglass because the performance method can be used to pass code. In theory, flash and batt meets prescriptive code for new construction walls. What is Flash and Batt Insulation? We’re going to look at the best insulation options for metal garages and steel buildings. You must be a magazine subscriber to access this feature. - Michael Schrauben. Let me know about my intent, your intent the codes intent. Knauf Insulation R-6.7 EcoRoll Unfaced Multi-Purpose 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. Second: I disagree with your statement that "Unless airtight AND heated, the attic will eventually reach temperature equilibrium with the outside." The problem arises with moisture. But the attic will never be at the same temperature as the outdoors. Although this method is one way to meet code and cut costs, there are problems with this model that we will get into shortly. If less than the required 2-inches of closed cell is installed, an air seal isn’t created, which defeats the whole purpose. You wrote, "My limited experience with inspectors leads me to believe the large majority of them will require continuous insulation (i.e., batts in direct contact w/foam) to meet the R-38 value. One possible design solution involves what is known as “flash-and-batt” where two inches of closed cell spray foam insulation is applied to steel siding interior surface between barn style wall girts, then balance of insulation cavity is fitted with fiberglass … check out the learning center on our website. … "If I install polyisocyanurate on the rafters, does it need to be covered with drywall (to protect against fire), and if so, would using XPS avoid that problem?". "There seem to be gaps in the wood on the roof; is it okay to spray foam on the underside of tar paper, or does the wood need to be continuous?". Foam board insulation can add insulation and eliminate thermal bridging when used in wall and ceiling assemblies insulated with batts… Don’t worry, we’ll break it down for you in a way that you can understand. A comprehensive roofing specification writing tool allowing users to quickly write accurate steep- and low-slope roofing specifications for job submittal packages. A. agreement The cost to insulate the wall cavities in a 2,000-square-feet home with flash and batt would be between one-third to half that cost of insulating properly with spray foam alone. For Martin an insulation technique that combines the air-sealing superiority of spray foam insulation with the cost benefits of fiberglass batts. "What would happen in your discussion of defining an R-20 wall if I used 2x8 or greater studs w/R-19? Flash and batt is a combination of spray foam insulation with fiberglass batts. Uneducated/Inexperienced Point of View Second, if I use spray foam and batts, how thick should the spray foam be (I'm assuming enough to provide airsealing qualities, but not compress the batt insulation). Would the resulting air gap between the insulation and sheathing or drywall add, reduce, or have no impact on the R rating (understanding the thicker wood gives me a little more R)?". She also loves knitting, making art, cooking, and hosting dinner and a movie night for friends and family. Pro: Sprayed foam insulation can be twice as insulating as batt insulation… hbspt.cta._relativeUrls=true;hbspt.cta.load(2621536, '247ee566-4364-41a9-a47a-81b7a75920b2', {}); Amanda previously has worked as a breaking news and crime reporter, TV news producer, and editor in Flint and Detroit. Sure, everyone wants to save a few bucks, but you will need to decide if it is worth it considering the potential long-term problems that can arise when an air seal isn’t achieved. Prior to hanging ceiling drywall, install rafter baffles, to preserve ventilation from soffit vents at eave of roof. Quick and easy online tools and calculators that can help you determine your insulation … While it’s important to understand R-Value, it isn’t always the revered determiner of insulation most people think it is. Michael Maines, an architectural designer, responds: Flash and batt or flash and fill can work just fine in an attic floor. Get building science and energy efficiency advice, plus special offers, in your inbox. The moisture is held in place by the insulation… (12-Bags) (69) Model# 10003-01316 $ 829 00 /pallet. I will also add my two cents to AJ's comment about Brownell. If the outdoor temperature is (for example) 10°F, then the temperature of the attic will be somewhere between 72°F and 10°F. Rigid foam board is just above the roof deck, or an exterior insulation option. You have one barrier of 5 and another of 13. Installed insulation R-value:The installed R-value is approximately R-12 for two inches of high density spray foam (2.0 pcf) and R-13 for three and a half inches of fiberglass batt, totaling R-25. That 2-inches of closed cell is about an R-14 in the walls and prescriptive code in Michigan for walls in new construction is R-21. The Society of Professional Journalists - Detroit Chapter. That insulation would have an R-value of about R-19 or R-20. This will happen if an air seal isn’t created in the wall cavity. Amanda Ringler on February 13th, 2018, fiberglass insulation | Spray foam between the studs can reduce air leaks, but a continuous layer of exterior rigid foam makes more sense than flash-and-batt, Choosing between a conditioned or unconditioned attic hinges on the merits of spray foam insulation, The installation quality of fiberglass batt jobs just isn’t getting any better around here — even in homes seeking LEED certification, This oddly illicit-sounding insulation system is becoming more common. The air gap you describe is undesirable, for two reasons: (1) The possibility of convective looping in the air space, driven by the difference in temperature from one side of the cavity to the other, and (2) The high likelihood that there will be enough air leakage in the assembly to allow outdoor air to reach the cavity, lowering the thermal performance of the wall assembly. 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