Unvented attics (UVAs) insulated with spray polyurethane foam (SPF) can help improve the energy efficiency performance of a home or building. UVAs move the insulation and air barrier from the attic floor to the underside of the roof deck. Transferring this system to the roof brings the attic and any equipment and ducts inside the building’s conditioned space. This helps to improve the energy performance of the building by reducing temperature fluctuations in the attic and energy loss that can result from leaky ductwork.
Insulation professionals can apply SPF insulation directly to the roof deck and other attic areas creating a UVA. The use of SPF insulation can also help tie together the attic and wall insulation, creating a continuous insulation system in the building envelope.
SPF is an ideal choice for UVAs because it acts as an insulation and air sealant. SPF expands on application, filling gaps and sealing air leaks in the attic walls and roof. This helps prevent air infiltration and can reduce air-conditioning loads providing further reductions in energy consumption
A UVA with SPF helps lower energy usage in multiple ways.
Compensates for leaky ductwork in the attic space – Duct air leakage commonly exceeds 20 percent of conditioned air flow, which results in a significant energy loss when ducts are in unconditioned space.
UVAs can capture air loss from leaky ductwork and return the air into the conditioned space.
Reduces the loss of conditioned air through the attic (stack effect) – Like a hat on a cold winter day, UVAs help reduce energy loss through a home’s attic. An UVA can keep a home warmer in winter and cooler in summer, reducing the HVAC load1.
UVAs in most cold climates decrease the heating load by about 10 percent2.
Both new and existing construction can be designed for UVAs, meaning all homeowners have the opportunity to benefit from energy savings.
New Construction – In a new building, the UVA can be installed during the construction process with SPF applied directly on the underside of the attic walls and roof. This installation allows for maximum coverage and air sealing.
Existing Construction – In an existing building, SPF is an exceptionally well-suited product for converting a traditional attic to a UVA. The spray application for SPF allows the product to be applied around any existing obstacles and into the hard-to-reach spaces of an attic.
To ensure that SPF is properly installed, it is important to choose a properly trained installer. A trained SPF contractor can answer your questions on product selection and application process. When considering a UVA in an existing home, it is important to coordinate with other experts, such as the HVAC contractor, to ensure the entire system works together to create a more efficient building envelope3. Always follow the state and local building code requirements.
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