Conflict with the Intent!

Leslie,
Page 225 of the CI reference guide might explain why this is happening, but the rationale is a bit confusing.

In the % reuse calculation, the "Total Retained Components Area (sf)" is the numerator. The denominator is *either* the "Prior Condition Area (sf)" OR the "Completed Design Area (SF)" depending on which is larger. (All areas are surface areas)

Say, in one scenario, you retain 900 sf of the existing 1000 sf of interior walls. You'd think your reuse would be 90%. But if you now build an additional 1000 sf of new interior walls, say for additional offices or conference rooms your reuse percentage goes down to 45%. That's not what I expected either.

The Ref. Guide states:
"By using the larger of the 2 values in the denominator, this equation puts projects that have minimized materials use in the completed design on a level playing field with projects that have optimized reuse of components from the prior condition."

Thus, projects that have optimized reuse of existing components only get credit for that if they *also* minimize materials in the completed design. The more materials are used in the completed design, the more your percentage of reuse will go down.

The credit requirements state: "Maintain at least 40% or 60% of the existing non-shell, non structural components (e.g., walls, flooring and ceiling systems. The minimum percentage interior component reuse for each point threshold is as follows: Interior Reuse: 40%, 1 point, 60%, 2 points."

I think many of us have interpreted "40% or 60% of existing" to mean we only look at the percent retained of the existing "Prior Condition Area," regardless of how much material surface area is in the final completed design. The requirements here don't say "have 40% or 60% of the Completed Design Area material area consist of Retained Components."

It's worth noting that in CI v2.0 Reference Guide the credit requirements and calculations for this credit are defined essentially the same as they are in CI 2009. And in NC 2.2, for credit 1.3 it says to "use existing interior non-structural elements in at least 50% of the completed building," which is what we're finding this credit to be pushing us toward. So there is a precedent for the credit working this way.

The credit intent is to "conserve resources, reduce waste and reduce environmental impacts of new buildings as they relate to materials manufacturing and transport." So maybe it's appropriate for a project that both reuses interior components AND adds little new material to score higher than a similar project that reuses the same amount of existing materials, but uses more total materials. But since I can't think of other credits where we earn points for using less material overall is than if we use more materials, it doesn't seem fair to hold back points for doing so only on those projects that are pursuing the building reuse credit.