The following assemblies address building enclosure components that are reasonably common but may not be represented in every home.

Overhanging Floor

In a project that includes a retrofit of the exterior walls, all above-grade overhangs should also be included in the DER. Configurations where these overhangs occur include the second floor overhang of a garrison colonial house, the underside of a projecting bay, the ceiling of an inset porch, and the ceiling of a vented crawlspace with conditioned space above. The following DER overhang assemblies support these conditions.

Overhanging Floor 1: Rigid Insulation Below Framing and Cavity Insulation, Finish Material to Underside of Overhang

• This assembly is typical for a porch ceiling under conditioned space or the overhang of the second floor of a garrison colonial.
• The existing finish is removed to minimize the change in elevation of the overhang.

Overhanging Floor 2: Closed-Cell Spray Foam Insulation in Cavities and Encapsulating Framing

• This assembly is typical under a first floor bay or for a vented crawlspace with conditioned space above.
• Encapsulation of the framing is required here to decouple the framing from the ground and crawlspace thermal and moisture conditions.
• The standoffs may be replaced with 2x2 furring if needed for attaching the protection layer (e.g. cement board).

Separations between Conditioned Space and Garage

Even a partial DER increases the airtightness of a house and thus changes the dynamics of the existing enclosure. If the house has an attached garage, steps must be taken to ensure that the combustion safety and health of the house occupants will not be compromised by the DER. At a minimum, fire protection as required by the applicable code must be provided. In addition, airtightness of all walls and ceilings and doors which are common between the attached garage and the interior of the house should be verified and improved, if needed.

If the DER project includes an upgrade of the exterior walls, then any garage walls or ceiling that are common between the garage and the house should be included as part of the DER project. The retrofit assembly differs from that for exterior walls and overhangs in that the fire protection requirements must be met and the water control function is not required because there is no direct exposure to the weather.

Garage Wall 1: Insulating Sheathing and Fire Protection Layer Installed Over Existing Wall

• This assembly is for common/shared wall between the interior of the house and the interior of an attached garage.
• If the existing garage wall finish is removed, the innermost layer of insulating sheathing will need to be detailed as the air control layer in which case the insulating sheathing must be foil-faced polyisocyanurate or XPS with seams taped.

Garage Ceiling 1: Insulating Sheathing and Fire Protection Layer Installed Over Existing Ceiling

• This assembly is for a garage ceiling when a portion of the interior of the house is located directly above the attached garage.
• Blocking will be needed for reinstallation of existing services and attachments on the ceiling.
• If the existing garage ceiling is removed, the layer of insulating sheathing will need to be foil-faced polyisocyanurate or XPS and detailed as the air control layer with seams taped.