It is an issue of size. We are well aware of what happens when the CFA of a home moves from 4000 sf to 6000 sf. The HERS Index goes down, a lot of that is what happens with the increasing volume and the effect on infiltration.
The same problem happens in reverse with a smaller size. Additionally, the decrease in the size of the envelope is also a significant factor. When you drop 50% of the square footage of AGW from a 1250 sf single family home, to a 1250 sf apartment - It becomes progressively harder to get the 50% reduction in envelope loads.
Got to ask, have you looked into the commercial version
You mean the 179 D tax credit for commercial? it is available in 3 pieces; Equipment, Enclosure and Lighting. You might get equipment and lighting. Enclosure could be subject to the above.