All of the above: Unburdening overburden considerations for commercial roofing

{"version":"0.3.0","atoms":[],"cards":[["images-card",{"images":[{"url":"http:\/\/res.cloudinary.com\/dpcbzfiye\/image\/upload\/v1660853708\/cmkqukxr8udjdp8ntoof.jpg","id":"6536026"}]}],["images-card",{"images":[{"url":"http:\/\/res.cloudinary.com\/dpcbzfiye\/image\/upload\/v1660853769\/rs6suplmk1re0dckmlyx.jpg","id":"6536027"}]}]],"markups":[["i"],["em"],["b"],["a",["href","https:\/\/continuingeducation.bnpmedia.com\/courses\/gaf\/all-of-the-above-unburdening-overburden-considerations-for-commercial-roofing\/","target","_new"]]],"sections":[[1,"h2",[[0,[],0,"Once thought to be a \u201cburden\u201d for a roofing system, overburden benefits are increasingly emerging as a roofing advancement that\u0027s here to stay. AIA partner GAF explains why selection of the overburden system is only part of the design; selection and design of the roof membrane is critical for a long-lasting performance."]]],[1,"p",[[0,[],0,"Since its inception, a roof\u2019s primary purpose has been to shelter its inhabitants from the elements, but now the underutilized potential of roof surfaces is being realized. Roofs with overburden can make a significant impact on the sustainability goals of a building, including increased energy efficiency, stormwater retention, energy generation, biohabitat restoration, food production, reduced urban heat island effect, and outdoor space."]]],[1,"p",[[0,[],0,"However, selection of the overburden system is only part of the design. Selection and design of the roof membrane, the waterproofing layer that protects the building, is critical for long-lasting installation and performance. Appropriate selection of the entire assembly, including proper detailing, is paramount to the overall success and longevity of the overburden system."]]],[1,"p",[[0,[0,1],2,"Overburden assemblies"]]],[1,"p",[[0,[],0,"Overburden is material or equipment that is located above the roof assembly. While each property is unique, there are many overburden options such as vegetative roofs, blue roofs, blue-green roofs, purple roofs, and rooftop solar. "]]],[1,"p",[[0,[0,1],2,"Roof system considerations"]]],[1,"p",[[0,[],0,"The overburden\u2019s success depends on the roof assembly beneath. Failure of the membrane, whether it requires repair or replacement, may necessitate removal of the overburden. The removal of the overburden can result in lost energy generation for solar installations and loss of rainwater capture for both vegetative and blue or purple roof assemblies. "]]],[1,"p",[[0,[0,1],2,"Membrane selection"]]],[1,"p",[[0,[],0,"Both single-ply membranes and modified bitumen roof systems can be an excellent choice for overburden installations as there are a wide range of application options that can be tailored to suit each installation. The type of overburden will determine whether the membrane should be installed at the deck level or at the top of the assembly. Membranes that will be used at the deck level, such as for vegetative assemblies, should be evaluated for durability and longevity since access to them for repairs will be limited and costly. Membranes where overburden systems, such as solar, are installed directly on the membrane should be able to withstand abrasion and puncture from roof elements above it. For blue roofs and water catchment systems, single-ply membranes are commonly used at the top of the assembly, and it is recommended that they meet NSF P151 water potability standards."]]],[1,"h3",[[0,[2],1,"Membrane color "]]],[1,"p",[[0,[],0,"For roof assemblies where the membrane is exposed and at the top of the assembly, such as for solar panel installations and blue roof assemblies, the color can have a significant impact on the performance of the system and also on roof surface temperatures. Reflective roof membranes can lower the ambient roof temperature. Using a lighter colored roof can decrease the urban heat island effect in cities and also may decrease the amount of heat that is able to radiate into a building\u2019s interior. Vegetative roof systems can take advantage of reflective membranes in areas where vegetation is not installed. "]]],[1,"h3",[[0,[2],1,"Membrane attachment"]]],[1,"p",[[0,[],0,"The attachment method of the membrane, whether mechanically attached or adhered, should be decided. Mechanically attached single-ply systems are subject to billowing in high-wind events. Over time, billowing can cause stress and fatigue on the mechanical attachments and membrane. Overburden installed over mechanically attached systems may billow with the roof membrane during high wind events, causing abrasion of the membrane surface. The overburden may also experience stress and fatigue due to movement, which could decrease their overall service lives. "]]],[1,"p",[]],[10,0],[1,"h3",[[0,[2],1,"Insulation"]]],[1,"p",[[0,[],0,"Insulation is critical in roofing assemblies for overall energy efficiency of the building. The higher the R-value, expressed per inch, the better the thermal performance of the insulation and its effectiveness at maintaining interior temperatures. Higher R-value per inch means less material is required to achieve the desired insulating value. Insulation boards are required by code to be installed so that the joints are staggered and offset, and several layers of insulation should be installed rather than just one thick layer. "]]],[1,"h3",[[0,[2],1,"Coverboards"]]],[1,"p",[[0,[],0,"Inclusion of a coverboard must be considered after selection of the overburden. Rooftops with overburden assemblies generally have increased foot traffic on the roof. Coverboards provide added protection against added foot traffic, penetrations (including from tools dropped by service contractors), wind-borne debris, and hail. "]]],[1,"p",[]],[10,1],[1,"h3",[[0,[2],1,"Overburden layout, details, and flashings"]]],[1,"p",[[0,[],0,"Qualified design and construction professionals should be involved throughout design and construction phases of roof and overburden systems. Inadequate detailing or termination heights leave the roof assembly vulnerable to leaks. Improperly detailed or flashed components may be water-tight for a period of time, but will most likely fail prematurely. Removal of the overburden system for repairs can be an added difficulty and substantial cost. It is good practice to allow penetrations, flashings, expansion joints, drains, and other critical roofing interfaces to be accessible for maintenance and repairs. "]]],[1,"h3",[[0,[2],1,"Summary"]]],[1,"p",[[0,[],0,"While the roof is the primary defense to prevent water entering into a building, this previously underutilized asset is being recognized by owners for the sustainability opportunity and the additional space that the roof offers. Once the overburden type is selected, the roof assembly needs to be determined, which depends on the type of overburden and the ultimate use of the roof space. The overburden\u2019s success depends on the roof assembly beneath. Roof assemblies should be installed to match or exceed the service life of the overburden systems; special consideration should be given to roof assembly design decisions as the overburden success is dependent on the success of the roof beneath them."]]],[1,"p",[[0,[0],0,"Want to know more? "],[0,[3],1,"Read the full article"],[0,[],1," and earn 1 AIA HSW LU."]]],[1,"p",[[0,[1],1,"AIA does not sponsor or endorse any enterprise, whether \npublic or private, operated for profit. Further, no AIA officer, \ndirector, committee member, or employee, or any of its component \norganizations in his or her official capacity, is permitted to approve, \nsponsor, endorse, or do anything that may be deemed or construed to be \nan approval, sponsorship, or endorsement of any material of construction\n or any method or manner of handling, using, distributing, or dealing in\n any material or product."]]]]}