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Conservation: Be Smart & Build Smart
Built Smart Users Manual: Specifications Appendix C:
Elevated Residential Slab Insulation Calculations
Built Smart Users Manual | Specifications | Alerts | Water
If the elevated residential slab (ERS) is not insulated to BUILT SMART minimums because you have calculated the required ERS insulation out through a trade-off of another measure at a higher level than is required by code, then you must:
  • Show your BUILT SMART representative what measures were used to calculate out the required ERS insulation. (NOTE: If you calculated out the required ERS insulation by installing another measure at a higher level than is prescriptively required by code, the building may be eligible for BUILT SMART incentives, except for the units directly above or below the ERS.)

  • If better window U-values were used in order to calculate out the ERS, the following equation shall be used to determine BUILT SMART incentives (if any):

    A - (C - I) = U

    Where:
    A = 0.36, assumed 0.40 code standard practice U-value
    C = The maximum U-value needed to meet code
    I = The U-value proposed to be installed
    U = The U-value which determines the BUILT SMART incentive - see table in Appendix D.
Example
If the builder was required to install minimum U-.35 windows in order to calculate out the ERS insulation for code:

Option 1
But the builder proposes U-.30 windows to qualify for BUILT SMART, then:

0.36 - (0.35 - 0.30) = 0.31

The windows qualify for a U-.31 incentive. (See table in Appendix D.) Note: The windows on the first floor would not be paid an incentive due to the reduced performance of the uninsulated slab floor.

Option 2
But if the builder proposes U-.33 windows to qualify for BUILT SMART, then:

0.36 - (0.35 - 0.33) = 0.34

The windows do not qualify for an incentive because BUILT SMART requires a minimum of U-.33 after the calculation. (See table in Appendix D.)

Interested in BUILT SMART incentives?
Contact Peter Held at peter.held@seattle.gov or 206.684.3605. For affordable housing projects, please contact Lisa Frasene at lisa.frasene@seattle.gov or 206.684.3182.

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