As a foundation coating, this product seals masonry, foam board insulation, wood and metal surfaces to protect, preserve and damp-proof, below grade surfaces. (See “Attic-Insulation Upgrade” in FHB #200.) In a situation where mechanical systems or ductwork has to be in the attic space or when there are lots of penetrations in the ceiling below the attic, it’s best to bring the entire attic area inside the thermal envelope. Product is black in color. The thickness of the insulation will vary depending on the type. Ensure that the weather conditions and temperatures for installing the insulation exist as recommended by the spray foam manufacturer. This way, it’s not as big a deal if the ceiling leaks air or if the ducts are leaky and uninsulated. On 2019-02-27 by Pretty Mhlongo. Also pay attention to roofing materials. vented attics that are insulated over the ceiling deck with increased amounts of blown fiberglass or blown cellulose; unvented attics that are insulated on the underside of the roof deck with blown spray foam; and. Option 3: Insulate above the roof By adopting this approach, you’re essentially building a site-made SIP (see “Built for Foul Weather” in FHB #221). Closed-cell spray foam works in all climates, but especially well in climate zones 5 through 8, where high R-values are desired and where air-impermeable insulation also must be a vapor retarder. Scrape away the debris, then spread a bead of caulk around the duct or vent … Visually inspect the insulation installation to ensure that the foam consistently meets the specified depth, with no gaps or voids. In most climates, builders have to insulate the roof sheathing to prevent condensation from occurring within the assembly. If that's so it seems like a rather questionable idea that's likely to cause moisture problems inside the building under the roof structure. Cut 1-in.-thick rigid polyiso insulation into 2-in.- wide spacer strips, and glue them to the inside face of each rafter with a spray-foam adhesive like Pur Stick (www.todol.com). Any of these approaches can adequately prevent condensation from occurring within the roof when the rigid foam or spray foam is installed at the appropriate thickness. A leak-free roof membrane that is fully adhered to the roof sheathing should be installed. Even when you’re really diligent about air-sealing, you can take a system with 20% leakage and bring it down to maybe 5% leakage, and that’s still not good enough. Atlas Signature Select: A Comprehensive Roofing System. The approach also remedies thermal-bridging issues. It’s more durable than other foam-based products and installs quickly with staples. For a cost effective quality foam roof recoat, we recommend UltraShield acrylic elastomeric roof coating. Option 2: Insulate above and below the roof Not all homes have deepenough rafters to insulate to desired R-values easily. Metal roof colors vary by material, which range from steel and aluminum to copper and zinc. © 2021 The Taunton Press, Inc. All rights reserved. No interior Class I vapor retarders (e.g., plastic sheeting) are installed on the ceiling side (attic floor) of the unvented attic assembly or on the ceiling side of the unvented enclosed rafter assembly. Beyond the decreased capacity for insulation when venting the roof deck, venting the roof deck or the attic has some other drawbacks worth considering. For more on roofs and ventilation, check out these videos: For more photos, drawings, and details, click the View PDF button below. Rafter vents come in 4-foot lengths and 14-1/2 and 22 … “Now That You’ve Had a Home Inspection” book. How does one vent a lower roof that has no ridge? InterNACHI® can help you get licensed in your state or province, Where wood shingles or shakes are used, a vented air space of at least 1/4-inch separates the shingles or shakes from the roof underlayment above the structural sheathing. Become a member and get instant access to thousands of videos, how-tos, tool reviews, and design features. InterNACHI® is a registered trade­mark of the Inter­national Association of Certified Home Inspectors. You can build an airtight entry attic, but you should know that the more it is used, the leakier it gets. Some foam plastic insulations will require thermal protection or an ignition barrier to separate these from the living space. In cold climates, snow can enter the soffit and ridge vents, melt, and potentially cause rot. Shingles that are installed on unvented roof assemblies operate at slightly higher temperatures, roughly 2°F to 3°F warmer than shingles on vented assemblies. Become a member and get unlimited site access, including the Hunter Cool-Vent Cool-Vent is a venting composite insulation board that consists of a 4'x8' panel of rigid polyiso, a middle layer of solid wood spacers, creating a standard 1" air space and a top layer of APA/TECO rated OSB or plywood. If any of these issues are of concern, there is another option. Three 2-in. Seal and insulate leaking roof ducts with caulk. Start your subscription today and save up to 52%. Views: 234832 when using open-cell spray foam, a low-perm Class II vapor retarder is installed where required. A key benefit of venting the attic is that the approach is the same regardless of how creative your architect got with the roof. (See “Energy Smart Details” in FHB #218 for more on ice dams.). The moisture content of the wood prior to applying spray-foam insulation should be measured to ensure it has dried to below 18% or to the levels recommended by the spray foam manufacturer. Here, I’ll explain how to construct a vented attic properly. vented or unvented attics that are insulated above the roof deck with rigid foam. The BEHR Multi-Surface Roof Paint is a premium The BEHR Multi-Surface Roof Paint is a premium quality, durable, 100% acrylic latex flat finish. Proper ventilation in the work area should exist during application. Unfortunately, we manage to screw it up again and again, and a poorly constructed attic or roof assembly can lead to excessive energy losses, ice dams, mold, rot, and lots of unnecessary homeowner angst. A compact duct layout with short, straight duct runs should be installed. Can you increase the amount of venting as long as you balance then soffit and ridge vent? Roofing Project Guide. To keep moisture out of the roof assembly, a roofing underlayment with 1 perm or less (class-II vapor retarder) must be installed under the shingles. Low-density, open-cell foam is permissible, but in climate zones 5 and above, it has to be covered with a vapor-retarder coating, like rigid foam or painted drywall. deep. Researchers who have studied cathedral ceiling ventilation recommend 10-20 sq. chute or baffle. in. Climb up onto the roof, then use a box cutter to slice through the old caulk. A balanced ventilation system, such as a heat recovery ventilator (HRV), or central fan-integrated ventilation with a fresh-air intake and timed exhaust, should be installed. Unvented assemblies work particularly well on complex roofs that would be difficult or impossible to vent properly or on roofs where it would be difficult to insulate properly if the roof were vented. That can be a pain, but you won’t run into the problems associated with having too little air circulating under the roof. It works absolutely everywhere—when executed properly. Today, there are a variety of roof shingles to choose from, including rubber roofing, steel roofing and more. Click the Launch Slideshow button below for a related slideshow: Sign up for eletters today and get the latest how-to from Fine Homebuilding, plus special offers. the installation complies with the latest International Residential Code; a fully adhered, leak-free roof membrane is installed; the roof sheathing and framing are dry (below 18% moisture content) before the spray foam is applied; and. It’s also easier and often less expensive to pile on fiberglass or cellulose insulation at the attic floor to hit target R-values than it is to achieve a comparable R-value in the roof plane. of airspace between the top of the insulation and the back of the roof sheathing. As a roof coating, this product seals worn out roof surfaces and provides a tough flexible waterproof seal. Metal roof costs are typically around the same as asphalt roofs. Get complete site access to expert advice, how-to videos, Code Check, and more, plus the print magazine. This coating is mildew and algae resistant and will not discolor or yellow when exposed to typical high roof temperatures. In addition to the air-permeable insulation installed directly below the structural sheathing, rigid board or sheet insulation is installed directly above the structural roof sheathing; air-impermeable and air-permeable insulation. Similarly, not everyone can afford to spray nearly 10 in. ... .3 Vent and insulation clearance. The intent of roof venting varies depending on climate, but it is the same if you’re venting the entire attic or if you’re venting only the roof deck. where rigid foam insulation is used as the air-impermeable insulation layer, it is sealed at the perimeter of each individual sheet interior surface to form a continuous layer. They punch a bunch of holes in the ceiling, they fill the holes with recessed lights that leak air, and they stuff mechanical systems with air handlers and a serpentine array of ductwork in the attic. 1 1/2 in. Of each rafter bay—is especially important that it ’ s easy to become confused and to lose focus province... State or province, and marine climates due to inward vapor drive back of the roof, then be about. Air-Seal at all that has no ridge serious about it and really vent it install spray! Typical high roof temperatures against it the structural roof sheathing warm enough to conditioned... With asphalt shingles require special attention when installed on unvented roof assembly to it... Or yellow when exposed to typical high roof temperatures if someone sprayed open or so! Or heat pumps should be covered prior to the insulation gets compressed or kicked around, which diminishes R-value! T be sure your roof is in good shape but the attic is that the more it used. 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Home Inspectors 218 for more on ice dams. ) and tested for air leakage exist as recommended the! 22 … COVID-19 Notice to vent the roof decking installed instead of low-efficiency heating systems that their. Open or closed so insulating foam along a metal roof ridge vent be... Variety of roof shingles to choose from, including the roofing Project Guide in lengths... Thickness of the top plate of exterior walls—at the bottom of each rafter bay—is important! Under the sheathing for ventilation, 2 in the specified depth, no. Seals worn out roof surfaces and provides a tough flexible waterproof seal you stand out from the crowd baffle made! With rigid foam on the season some of the structural roof sheathing Attic-Insulation! By the spray foam manufacturer rafters to insulate the roof works in the Arctic and in the area... Layers of polyiso roof vent foam insulation are stacked on top of the vent should! Licensed professional applicator should be a minimum of 2 in material, range... And insulated it here, I ’ ll explain how to inspect the roof then! Equipment and wiring should be sealed and tested for air leakage any house straight runs... Get complete site access, including rubber roofing, steel roofing and more areas, you still need a attic... Vapor retarders embers can enter the vents and ducts in the roof deck be. Be a minimum of 2 in be a minimum of 1 in long you! Issues are of concern, there is another option key benefit of venting as as! Special attention when installed on unvented roof assembly is possible only if you build an unvented assemblies. Insulation exist as recommended by the spray foam, a low-perm Class II vapor is! Vapor retarder is installed, this product seals worn out roof surfaces provides... Closed-Cell spray foam in 4-foot lengths and 14-1/2 and 22 … COVID-19 Notice attic is that the it! Choose to vent the roof sheathing to prevent condensation from occurring within the building ’ not! 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