All,

Can anyone share their experience with the modified baseline model HVAC description in ASHRAE 90.1 - 2007 and 2010? (copied below) ASHRAE 90.1-2004 did not require the baseline model for systems 5,6,7 and 8 to have separate HVAC systems per floor and I'd like to hear how people have interpreted this and, if anyone can explain the reasoning for this.

For example, the proposed model of a 15 story office building might have 2 AHUs, one serving the east wing and one serving the west wing. For the baseline per ASHRAE 90.1-2007 or 2010, will these 2 AHUs be replaced with 15 separate VAV units? Or can the 2 AHUs be kept as long as it satisfies the statement "Floors with identical thermal blocks can be grouped for modeling purposes"?

ASHRAE 90.1 - 2004
G3.1.1 Baseline HVAC System Type and Description.
HVAC systems in the baseline building design shall be based
on usage, number of floors, conditioned floor area, and heating
source as specified in Table G3.1.1A and shall conform
with the system descriptions in Table G3.1.1B.

ASHRAE 90.1 - 2007 and 2010
G3.1.1 Baseline HVAC System Type and Description.
HVAC systems in the baseline building design shall be based
on usage, number of floors, conditioned floor area, and heating
source as specified in Table G3.1.1A and shall conform
with the system descriptions in Table G3.1.1B. For systems 1,
2, 3, and 4, each thermal block shall be modeled with its own
HVAC system. For systems 5, 6, 7, and 8, each floor shall be
modeled with a separate HVAC system. Floors with identical
thermal blocks can be grouped for modeling purposes.

Thanks!

Linda Lam