Revision history [back]

This is a general question, I would like to understand the reasoning behind it. I remember that 90.1-2004 did not have the "one system per floor" requirement and the zoning was the same as the design case. But starting 90.1-2007, the requirement became "each floor shall be modeled with a separate HVAC system". Thus the zoning is very different from the design case. And I personally feel it is very difficult to compare the two models (design and baseline) and do trouble shooting etc this way. Also the one system per floor does not seem to be a better representation of design in the actual world. Can anyone explain a little bit why they have this requirement? Thx.

This is a general question, I would like to understand the reasoning behind it. I remember that 90.1-2004 did not have the "one system per floor" requirement and the zoning was the same as the design case. But starting 90.1-2007, the requirement became "each floor shall be modeled with a separate HVAC system". Thus the zoning is very different from the design case. And I personally feel it is very difficult to compare the two models (design and baseline) and do trouble shooting etc this way. Also the one system per floor does not seem to be a better representation of design in the actual world. Can anyone explain a little bit why they have this requirement? Thx.