Here's a brain puzzler for the list.

I'm assisting a team designing an addition (auditorium + rehearsal space) to an existing high school in Connecticut. As a public project receiving state funding, CT's High Performance Building Standard applies which requires a 21% energy cost savings (LEED for Schools Silver is also targeted for the new addition only).

The new space will have independent/new ventilation systems, but will most likely utilize the boiler and potentially chillers of the existing school building.

Buried in ASHRAE modeling guidelines, we discovered (long after project started and engineers "completed" the model) that additions and alterations that share HVAC systems with existing spaces, are required to include those spaces in their energy model. The new space is designed for a 24% reduction - but if the existing spaces (approx. 3x the sf of new space) are included performance will fall way below the required threshold.

We can't understand how other LEED projects in similar situations ever meet energy reduction requirements, has anyone dealt with this on a LEED project and found ways to circumvent? Has anyone come across a similar condition, and if so - how did you approach it?

Many Thanks in advance -

Vikram Sami, LEED AP BD+C