Exterior Rigid Insulation Best Practices TOP INNOVATOR: BSC, PHI, NorthernSTAR Field studies by Building America’s research teams show the most effective ways to take advantage of the thermal, air, and vapor resistance properties of rigid foam insulation on walls, roofs, and foundations. 1679 Clearlake Road, Cocoa, Florida 32922 Phone (321) 638-1000, Oak Ridge National Laboratory, Building Envelope Programs (BEP) http://www.ornl.gov/roofs+walls/research/ We will be residing the cabin this summer and are wondering if adding 1 inch of XPS rigid insulation on the exterior walls and walk out will cause any moisture issues. If you want to move it out of the framing and sheathing everywhere, you have to add enough foam insulation everywhere to get it into the foam, all the time, regardless the temperature. Some builders use 2 layers of sheathing: a layer of plywood or OSB for structural support plus a seam-staggered layer of rigid foam insulation. When rigid foam insulating sheathing is installed on the exterior walls of a home, the foam can serve as a drainage plane, taking the place of house wrap for time and cost savings. It will take more than 15 years to recoup the cost of oil or natural gas at today’s prices. If the exterior wall sheathing is below the dew point temperature, condensation will form on the sheathing. The braces are only as strong as the nails used at the ends of the brace! Cementitious foam costs about $1.40 to $2 per square foot. This type of insulation can be more expensive than loose-fill insulation. All three types of rigid-foam insulation—expanded polystyrene (EPS), extruded polystyrene (XPS), and polyisocyanurate—are suitable for use on the exterior of walls and roofs, though they do not perform equally. I've been in plenty of these homes and can tell you that when spray foam is installed properly, they outperform 99% of fiberglass batt-insulated, stick-built homes. Use foam that's labeled for window and door insulating. Resource: BSC’s Guide to Insulating Sheathing. Polyisocyanurate products like Rmax Durasheath® (perm 1+/ inch) and Dow Sturdy-R (perm 3+/inch) are available too. The lower level has 2 in of XPS rigid foam insulation on the interior walls. P.O. Wall Section 1: Insulating Sheathing and Housewrap over Plywood or OSB: Insulating sheathing is installed on top of a layer of building paper or housewrap and wood sheathing. upgrade appreciates in value as energy costs rise. Adding Foam Insulation to Existing Walls with Slate Tile Siding. This document established 5,200 pounds as the acceptable base level of racking resistance for wood-framed walls. Some information contained in it may be outdated. This stucco layer goes straight onto a plastic foam board surface. In Stock at Store Today. Another alternative is spray foam insulation. - Housewrap is more exposed to exterior elements such as wind loading and moisture; may not be as durable as other approaches. Wrapping a home with insulating sheathing saves energy and can be cost effective, but the design must consider a host of structural concerns including moisture, shear loads, insects and fire. Each corner panel will resist an ultimate load of 3,120 pounds when nailed with 8d nails, spaced 6-inches at the edges and 12-inches in the field of the panel. Section R602.8 in the International Residential Code (and sections of other building codes) requires fire blocking at the bottom, between stories, every 10 feet, and at the top near the roof in concealed stud spaces, including furred spaces. It keeps the underlying structure warm and as a result drier. Center of Cavity value includes R-value of drywall, osb sheathing and wood siding. 11 Results Interior/Exterior: Interior/Exterior. http://www.wwpa.org/ Adding a layer of rigid foam to the walls of any building is somewhat labor intensive. Weigh the following pros and cons on a case-by-case basis and execute any plan with thoughtful details. Spray Foam’s affect on wall strength In a series of racking tests1, walls with and without spray-applied polyurethane foam insulation were compared. This 'minimal-expanding' type reduces the chance of warping the jamb. Using Building Energy Optimization (BEopt), thermal, hygrothermal and structural analysis, they came up with the optimal framed wall: - 2’ x 6’ advanced framing with 1.5-inch closed-cell spray polyurethane foam in each stud bay - 3 inches of cellulose insulation covered by 0.5-inch gypsum with latex paint finish - Diagonal metal strapping on the exterior - 1.5-inch foil-faced polyisocyanurate board insulation and exterior vertical wood strapping for cladding attachment.This wall had the lowest associated incremental cost, lowest associated air-leakage condensation risk at less than 1 percent of the year in Minneapolis, the best structural performance—based on American Society for Testing and Materials (ASTM) E72—and the second-best annual energy savings at 34 percent in Minneapolis and 29 percent in New Orleans. building paper; Textured plywood siding. Hide Unavailable Products. The conversion of regional wind or seismic exposures into an effective wall design is complicated and should be left to engineers. R-12 cavity + R-4 foam, 3.5” steel 24” o.c. ORNL scientists have developed a method to account for the thermal bridging of all framing and connections used in a typical wall. Depending on your climate, you might consider increasing stud depth and on-center spacing. Vented rain screens are correctly touted as a superior weather barrier system. - Higher risk; should only be used in areas with limited rainfall and exposure, where rainwater management is not as critical. Product Thickness (in.) Substitute insulating sheathing for plywood or osb in new construction and there is virtually no added cost. This creates an air space between the back of the siding and the face of the foam that drains and dries readily. It is graded for appearance. The FHA minimum value reflects the wind resistance provided by wood-framed walls, sheathed with horizontal boards and braced by 1″x4″ let-in bracing, a common construction practice in 1949. If you want to do your exterior wall a big favor, EIFS can come in handy. If you want to move it out of the framing and sheathing everywhere, you have to add enough foam insulation everywhere to get it into the foam, all the time, regardless the temperature. The greatest threat exists where the average annual outdoor temperature exceeds 50 degrees. If the crawlspace isn't ventilated, it may have insulation in the perimeter wall. The best way to minimize ant damage is to follow good ant prevention practices on the building site. Studies conducted by Oak Ridge National Laboratory (ORNL) shows that thermal bridging through the framing elements of a structure degrades the overall energy performance of a wall system. Check if the panels comfortably fit with the installed furring strips. The Vinyl Siding Institute recommends 3/4-inch nail penetration, but the International Residential Code requires 1 1/2 inch nail penetration for vinyl siding. We install the foam over a layer of house wrap using cap nails followed by taping all the seams with an approved foam insulation … hbspt.cta._relativeUrls=true;hbspt.cta.load(309276, 'c8fe45b7-9553-469d-884d-72f066621a26', {}); © 2020, Green Builder Media. Please note: This older article by our former faculty member remains available on our site for archival purposes. This means you must target the underlying studs even when foam overlays structural sheathing. Exterior Insulating Sheathing ScenariosAdding insulating sheathing to the exterior of the assembly is a simple method of increasing the overall thermal resistance of the wall assembly beyond what is possible with cavity insulations, thereby increasing the overall efficiency of the house. Tuomi and Gromala learned that much of a braced wall’s racking strength is owed to the interaction of board sheathing and let-in bracing. Mixed-humid climates: The assembly needs to be protected from wetting from both the interior as well as the exterior. FF-PIR insulation products can be used in exterior walls with various framework materials. As a nation, we spend two-thirds of our annual pest control budget on termites. and Ph.D.), Wood Engineering and Bio-Based Building Materials Specialization, Building Science and Green Building Specialization, UWW Professional Education and Online Courses, Certificate in Sustainable Building Construction, http://www.ornl.gov/roofs+walls/calculators/wholewall/index.html, http://www.ornl.gov/roofs+walls/research/, http://www.dow.com/products_services/industry/build.htm, Tedd Benson speaks about a better way to build in the 21st Century, Heidi Jandris speaks about lowering the embodied carbon of concrete masonry units, Register now for BCT’s Winter & Spring Online Professional Education Courses, Upcoming Talk: Building Operations during COVID (Wednesday Oct. 14th), 3.5” steel 16” o.c. So a wall (2 ends) will resist 6,240 pounds. A 3.5-inch steel-frame wall delivers only 45% (R-6.1) of the center-of-cavity value, just 59% of a wood-frame wall value. Drained insulation boards (ones with vertical grooves cut in the back) or vertically textured (or profiled) housewraps are recommended, to ensure a drainage space behind the rigid board. It was ant-chewed rigid foam insulation removed from the sidewall of a remodel job he was working on. Check your local code on this issue. However, figuring a payback for foam sheathing on a residing project is tricky. - Insulating sheathing essentially replaces the plywood or OSB in a traditional wall assembly. Philosophically, there is no question; saving energy is a good, healthy, enlightened practice. Department. He’s going to gut the room, but doesn’t plan to remove any exterior siding.His goal is to boost the R-value, and improve the air-sealing, in exterior walls by adding a layer of rigid foam insulation on the inside, after filling the walls with cellulose. Building scientists have learned that as airborne moisture leaks into wall cavities, so does heat that warms walls to safe levels. Adding most anything to the exterior moves the dew point further out. Some builders use 1/2-inch wood sheathing (R-0.6) or asphalt impregnated sheathing, usually called blackboard (R-1.3) to sheath the walls. The pros and cons of building an inside-out wall. When properly constructed, it provides a tight, dry, warm, and durable structure. However, other inspectors disagree and think the code section holds as written. It’s fast and easy, but you should still have an engineer review the plans to establish working design values. Homes that have slate tiles are similar to vinyl or aluminum siding. Adding a layer of rigid foam to the walls of any building is somewhat labor intensive. Interior Wall. The use of insulating sheathing is becoming popular as consumers and energy codes demand energy-smart details. Plastic foam traps heat and moisture beneath the siding. It is highly effective, but here are 2 issues to consider. Insulating power, or R-Value , is only one factor to consider when building or improving a … Will foam-sheathed homes perform as well? The list of variables is long. We will be residing the cabin this summer and are wondering if adding 1 inch of XPS rigid insulation on the exterior walls and walk out will cause any moisture issues. I am looking to add exterior rigid insulation to an existing house that is located right at the border of Climate Zones 4 & 5. What is the Best ‘R’ Rating for Insulation? http://www.vinylsiding.org/ A continuous layer of insulating sheathing applied to the exterior surface of a wall will minimize condensation and moisture levels. They merely use it for shelter. Some professionals argue this level of performance fails to meet at least the spirit of performance dictated by many building codes. Foam Insulation. Windows, doors and trim must be built out and the flashing sealed to the foam sheathing. Half-inch thick sheets can be installed vertically at the corners and overlaid with half-inch thick rigid foam. The lower level has 2 in of XPS rigid foam insulation on the interior walls. So run your rain screen design past the inspector before building the walls. Building codes may not allow you to leave an air space behind the siding. To serve as a drainage plane, the seams in the foam sheathing must be properly taped with sheathing and flashing tapes to provide continuity of the drainage plane at joints between panels. This article is the exclusive property of Green Builder Media. Tel: 503-224-3930, Dow, Building and Construction http://www.dow.com/products_services/industry/build.htm, Owens Corning, http://www.owenscorning.com/, 3M Contractor Sheathing Tape, 3M Construction Markets Division, St. Paul, MN 800-480-1704, TU-TUF 4 Tape, Sto-Cote Products, Inc., Richmond, IL 800-435-2621, INSULTAPE III, Conserv Products, Inc., Oregon, WI 608-835-7299. http://www.pima.org/ If you would like to reprint this content, you are free to extract a short excerpt (no more than 1/4th of the total article), as long as you 1. credit the author, and 2. include a live link back to the original post on our site. Company News. Cut the foam with the mark as guide you may use either a knife or saw to accomplish this process. ), which is a drainage plane that collects and drains water out of the wall. Foam insulation is probably the best retrofit choice in terms of avoiding wall damage. ORNL provides a free on-line calculator to predict the performance of various wall systems at http://www.ornl.gov/roofs+walls/calculators/wholewall/index.html. Remember the old adage, “When in doubt, always ask.” Certainly 1″x4″ let-in braces have worked well in the past. Any switch away from plywood to non-structural sheathing must be evaluated carefully. GBM Research. Furring that is only 3/4-inch thick does not provide the 1 1/2-inch nail penetration required by manufacturers and building codes. This represents an increase of 35 percent effective thermal resistance, with only 15 percent increase in the overall wall thickness. Research by several teams has provided the critical scientific basis for acceptance of foam sheathing by the codes community, and resulted in best practices for installation to ensure thermal performance—as well as air barrier and drainage plane integrity. : This was a lengthy project that involved carefully removing the Aluminum siding off of my house, installing 1inch thick foil faced foam insulation and replacing the Aluminum siding.I have a small house that originally had a stucco exterior… That’s like having one entire wall of a home with no insulation. One-inch thick foam can be used to sheath the remainder of the house, leaving the exterior wall surface flush. Termites can tunnel from the soil up behind the foam panels and attack the structure of a house without being noticed. Corrosion Resistant Exterior Insulation Finishing System Office bulding external wall decorative & insulation system. x 24 in. 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