Existing Building Renovation w/ a New Addition

What happens when you have a similar situation (existing building being rennovated with a new addition) but the entire HVAC system and building envelope are being replaced? Would you just consider the entire building as new?

Amanda, that sounds like a judgment call to me. If the envelope is being replaced, it does sound like it makes sense to call it a new building.

This raises a good question as to what constitutes an "existing building" for EAc1 purposes. If you gut the interior partions of a building and replace the mechanical systems, I'd call it 100% existing. If you then replace the windows, I'd probably still call it 100% existing. But what happens when you then replace or add insulation to the entire roof? That's the situation I am currently faced with. Is it still 100% existing? 0% existing? Or some % in between? I feel that USGBC needs to refine this definition of "existing" buildings as it pertains to EAc1 point thresholds in these grey areas. Any input into my situation would be appreciated.

I think if you are adding envelope components you are still altering an existing building. If you are adding an addition, e.g. new occupied space, then you are not 100% existing. So if you're adding insulation to the roof, you are still 100% existing, If you're building an insulated penthouse on the roof, that counts as addition. USGBC does allow for envelope improvements under MR Credit 1 for building re-use, I assume because they want to encourage upgrading the performance of building envelopes.