I have an existing building where we are remodeling 3 floors(Basement, 1st and 2nd).  The building is mixed use the first two floors are retail, basement is storage and the rest(about 18 floors) is residential space.

1st question: Do I have to model the entire building to meet this requirement?

2nd question: If I do have to model the existing building does the 15% requirement still apply?

3rd question: Since the building is existing(Does not currently meet 90.1-2007), Can I model the baseline as it currently stands or do I have to model the baseline with the fenestration requirements set out in 90.1?

Cheers,

Carlos Lopez