Explanation
The percentage rule is a method to determine the most appropriate LEED rating system for a project when several rating systems may be applicable1. To use this rule, first assign a rating system to each square foot or square meter of the building, and then choose the most appropriate rating system based on the resulting percentages1. 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 system1. The percentage rule states that if one rating system covers more than 60% of the gross floor area, that rating system should be used1. If no rating system covers more than 60% of the gross floor area, but one covers more than 40%, then that rating system should be used1. If no rating system covers more than 40% of the gross floor area, then the project team can choose any applicable rating system1. Therefore, the answer is B. 40/60 rule.
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LEED rating system selection guidance