The EST target u-value for the rafter-level insulation of a pitched roof is 0.20 W/m2K, though much higher values are achievable. Both these variants require different approaches to insulation which will be covered in this guide. If the roof is unvented, there are several ways to efficiently insulate the space either from the exterior, from the interior, or from a combination of both. The cost of taking off the top parts of a flat roof in order to add to the insulation may be costly, especially on larger commercial buildings. Exterior insulation permits high R-value to be achieved without necessarily disturbing interior finishes. An unvented attic differs from a conventional vented attic in that there is no direct venting of the attic space which is generally considered to be between the roof rafters/framing and the top story ceiling framing members (attic floor). Since it’s air impermeable, spray polyurethane foam can be installed alone on the underside of roof sheathing. These levels are rising on an ever increasing scale as the Government strives to meet its targets for reducing CO2 emissions. These assemblies are created by eliminating ventilation openings and moving the thermal, moisture and air control boundaries to the plane of the roof deck. When ductwork and mechanical systems are located in the roof, an unvented roof is generally preferred. Insulating Unvented Sloped Ceilings. Recently, Lorne co-led the development of the Illustrated Guide to R30+ Effective Vaulted & Flat Roofs in … The roof is … Warm flat roof insulation Hot roofs have several problems: Adding insulation to an existing flat roof is a labor-intensive process. We also have insulation boards suitable for more specialist roof applications, for example inverted roof insulation and balcony insulation. Un-Vented Roof Solutions: how to avoid condensation, leaks, attic mold, insulation mold, & structural damage to roof framing when roof venting is not possible - Detecting and Correcting Attic Condensation and Preventing Ice Dam Leaks in buildings can reduce the chances or correct the causes of mold in attics. Note that table R806.4 indicates the amount of insulation above the roof deck or air impermeable insulation below the roof deck required for condensation control assuming minimum required total insulation as indicated in Section N1102 Building Thermal Envelope. Is spray foam the solution? Murmurs and hearsay about open-cell spray foam insulation have been gaining traction for a while. Warm Flat Roofing: Insulation material is placed on top of the roof, rather than in-between the ceiling and the decking. Code specifies the minimum R-value of the rigid-foam layer. Unvented attics are not allowed by the building code yet in Canada but are allowed in the International Residential Code in the US in Section R806, which describes three different insulation strategies for unvented roofs. The 1x roofing boards (which also made up the “ceiling” of the garage) had nice gaps that you could see the ceiling joists … The ventilation allows the heat and moisture from the building to leave the roof, instead of creating moisture problems on the inside. The typical U-value of an existing, uninsulated flat roof is 1.5W/m2K. FHB's 40th Anniversary Tips Video Contest, Micro-Adjust Deck-Baluster Spacing for an Eye-Deceiving Layout. Get complete site access to expert advice, how-to videos, Code Check, and more, plus the print magazine. We agree that avoiding sheathing rot is critical, and that air permeable insulation such as fiberglass or cellulose cannot be used alone. There are typically no supply or return registers fr… Insulation, whether a single type or combination, must at least meet these requirements. Ensure that your new insulation doesn’t impact ventilation to protect your investment in your roof and your property. - M.K. Advice on insulating vented and unvented low-slope roofs applicable to both commercial and residential buildings. Unvented roof assemblies should be insulated either with air-impermeable insulation (rigid foam or spray polyurethane foam) or with a combination of foam and air-permeable insulation. The rule of thumb for foil faced boards (like Thermapitch TP10 or Kooltherm K7) in this scenario is that you can have no more insulation under the joists than you have between the joists. Afterall, it is expensive, particularly on a large commercial roof, to remove the top layer of the roof and then lay down new insulation. In association with. 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