Step 3 - Make a decision
When several rating systems may be appropriate, use the 40/60 rule
If the correct rating system is not obvious, for example, if different parts of the project are undergoing different kinds of construction or are serving different space usage types, carefully review the rule below.
Percentage of square footage appropriate for a particular rating system
- 0% to 40% Should not use that rating system
- 40% to 60% Project team's choice
- 60% to 100% Should use that rating system
The following “40/60 rule” provides guidance for making a decision when several rating systems appear to be appropriate for a project. To use this rule, first ‘assign’ a rating system to each square foot of the building based on the guidance in this document.
Example: LEED for Schools for an existing K-12 school undergoing major renovations and LEED for New Construction for an addition being built onto it. Choose the best rating system depending on the resulting percentages. Be sure to include the entire certifying square footage (but no more) in this exercise.
Keep in mind that the entire gross floor area of a LEED project must be certified under a single rating system, and is subject to all prerequisites and attempted credits in that rating system, regardless of a mixed construction or space usage type.
- If a rating system is appropriate for less than 40% of the gross floor area of a LEED project building or space, then that rating system should not be used.
- If a rating system is appropriate for more than 60% of the gross floor area of a LEED project building or space, then that rating system should be used.
- Project teams with buildings and spaces that do not fall into the scenarios described in 1) and 2) must independently assess their situation and decide which rating system is most applicable.
The 40/60 rule is not applicable to LEED CI and LEED CS. For additional guidance on using LEED CS versus another rating system, see LEED Interpretation 10102, and for LEED CI, see Step 1 of this guidance document.