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Lighting Seattle since 1905 Jorge Carrasco, Superintendent
Conservation: Be Smart & Build Smart
Built Smart Users Manual: Specifications Chapter 3:
Thermal Efficiency &
Insulation Details
Built Smart Users Manual | Specifications | Alerts | Water

The following required thermal efficiency details must be met when constructing a BUILT SMART building.

3.1 Roof/Ceiling Insulation Details
3.1.1 Minimum Attic Eaves Insulation. A minimum R-38 ceiling insulation is required over the entire ceiling in attic framed roofs, including over the interior edge of the exterior wall. The ceiling insulation shall be installed out to the outer edge of the exterior wall to the fullest depth possible. (When attic insulation is blown in any attic not framed with advanced framing all eaves must be insulated with minimum R-38 fiber glass batt insulation to a minimum of two feet in from the exterior walls.)
3.1.2 Recessed Fixtures. Recessed fixtures in exterior ceilings (e.g. exhaust fans, recessed lights, heating equipment) shall be covered by the full depth of insulation required by the component assembly. (See Section 3.5.6 for Air Sealing details.)
3.1.3 Hatches. Hatches connecting conditioned spaces to attics and crawlspaces shall be insulated to at least the minimum requirement for the appropriate component. The insulation shall be held in place in a permanent manner.
3.2 Wall Insulation Details
3.2.1 Exterior Wall Framing. All exterior wall framing cavities shall be fully insulated.
3.2.2 Exterior Wall Framing Headers. All headers shall be fully insulated to R-10, or maximum R-value possible in header cavity.
  • Greater than 2 inch header cavity = High Density Fiberglass allowed.
  • Less than 2 inch header cavity = 1.5 inch rigid foam required.
  • Less than 1.5 inch header cavity = 1 inch rigid foam required.
3.2.3 Rim Joists. All rim joists between floors shall be insulated to the above-grade wall R-Value. The insulation shall be installed in a permanent manner and include the required vapor barrier. All penetrations or openings in the rim joists between floors shall be fully caulked and sealed to limit air leakage.
3.2.4 Interior Stairwells and Elevator Shaft Walls. All interior stairwell and elevator shaft walls adjacent to any residential unit, or any other conditioned residential space, shall be insulated to a minimum of R-21.
3.3 Elevated Residential Slab Insulation
All elevated residential slabs must be insulated in one of the following manners for the residential units on that slab to be eligible for BUILT SMART thermal shell incentives.
3.3.1 When ERS and building shell footprints are equal and above:
  • Heated space. R-10 is required around the entire slab perimeter. (No under-slab insulation is required.)
  • Unheated space. R-10 is required around the entire slab perimeter and R-30 is required below the slab; OR R-15 is required above the slab.
3.3.2 When ERS and building shell footprints are unequal (slab footprint greater than the building) and above either heated or unheated space the entire residential building shell slab floor must be insulated to R-15 above the slab.
3.4 Door and Glazing Details
3.4.1 All windows and glazed doors shall be NFRC certified and labeled.
3.4.2 The window supplier is required to supply the BUILT SMART representative with a window schedule identifying total glazing square footage, window sizes, U-Value for each type of window/glass door, and average U-Value calculation.
3.5 Required Air-Leakage Control Details
Sealing is required.
3.5.1 Around all window and door frames to control air-leakage.
3.5.2 At all exterior penetrations in the rim joist framing including blocking where the floor joists are cantilevered to support an exterior deck.
3.5.3 At the bottom of the wall plate where wall meets the slab floor.
3.5.4 Around any penetrations in the building envelope to ducts, through-the-wall air inlet vents and access hatches.
3.5.5 Around all outlets, switches, or other electrical boxes in the exterior walls, ceilings or floors. (Foam gaskets behind electrical cover plates meet this requirement.)
3.5.6 For all recessed fixtures (e.g. wall heaters, exhaust fans, medicine cabinets, recessed lights, etc.): they shall be sealed to the assembly in all exterior walls and ceilings and in all ceilings between floors of stacked multifamily units.
3.6 Back Draft Dampers
Intermittently operated fans, or other non-heat recovery systems exhausting air from the building shall be ducted to the outside and have a back draft damper located in the exhaust duct.

Interested in BUILT SMART incentives?
Contact an Energy Advisor at
or call (206) 684-3800.

Contact an Energy Advisor at
or call (206) 684-3800

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