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What is an Unvented Attic Assembly and What Does It Do for Your Home?

By June 27, 2017September 19th, 2022News

Looking to reduce wear and tear on your HVAC system and create a more consistent climate in your home? An unvented attic assembly may be your answer – and it’s an insulation method that’s become popular in recent years.

An unvented attic differs from a standard vented attic in one key way. Simply put, an unvented attic does not have venting in the space between the roof rafters and the ceiling joists of the top story.

In an unvented attic assembly, spray foam insulation is applied directly to the underside of the roof deck and gable end walls and soffit area (different from a standard vented attic where insulation are installed on the attic floor). Spray foam is then tied directly into the wall insulation of the floor below. This ties the roofline directly into the building envelope, making the attic part of the insulated building enclosure.

An unvented attic results in the attic being “indirectly” conditioned space. Although there are no supply or return vents in the attic from the HVAC system, the system naturally conditions the space through natural leaks in the system structure. Unvented attics reduce energy consumption in three ways:

  1. HVAC equipment is placed in conditioned space with moderate temperatures, reducing wear and tear on the system.
  2. Any duct leakage remains within the conditioned space, reducing wasted conditioned air.
  3. Duct penetrations through the ceiling of the top floor of the house (directly below the attic) don’t negatively affect the air tightness of the building envelope, as the envelope has now moved from the attic floor to the roofline.

If you are interested in an unvented attic for your new home, contact our team to learn more.