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What are the common shell/building envelope mistakes in TREAT?

• Exterior walls in the conditioned space should not be entered as an open cavity, with the exception of kneewalls. Make sure open cavity kneewalls are adjacent to an attic, not the outdoors.

• All ceilings should be adjacent to an attic, not the outdoors. If there is no attic above a ceiling, then model it as a roof instead.

• Roof surfaces in the conditioned space should have a starting R-value of at least R-4. If there is any insulation on the ceiling below the roof, that should be reflected on the existing roof surface to represent the overall R-value of the whole attic.

• When dense packing, make sure the proposed insulation amount in TREAT does not exceed the size of the framing. For example, the proposed wall surface should not include any existing fiberglass, as it gets compressed during dense packing and adds little to the R-value.

• Do not include extra foamboard/fiberboard to the proposed R-value unless that is actually being installed with the cellulose or fiberglass.

• If two or more surfaces are getting different levels of insulation or different materials are being used, they cannot be lumped together in one improvement because the final R-values will be different.

• The rim joist should be modeled in the basement, not the first floor.

• Make sure there is at least one conditioned surface adjacent to each of the unconditioned spaces in the model, i.e. basement, crawlspace, garage, attics, porch, boiler room, etc.

• Basements should only be considered conditioned if they are intentionally heated or are within a few degrees of the first floor in the winter. Do not enter the basement as conditioned simply because the heating equipment or a laundry room is down there, as this can greatly affect the heat slope and estimated savings. The Minimum Ventilation Guideline in TREAT will also be affected.

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