Hi,
I did an equest model based on ASHRAE 90.1 2007 for LEED 2.2 EA prereq
2. Another credit IEQ 7.1 states that the building needs to abide by
ASHRAE 55 which requires a 1 degree driftpoint. I modeled the building
having a 2 degree driftpoint in equest, and I think I will not meet the
unmet hours requirement if I switch it to 1 degree.
Is this even necessary? IEQ 7.1 does not state that I need an energy
model, and EA prereq 2 does not state that I have to meet ASHRAE 55. If
I put a 1 degree driftpoint into equest it's going to go crazy.
Thanks!
Amanda E. Martz, EIT, LEED AP
Amanda,
By my inspection, your ASHRAE 55 requirement is not going to be a
1-degree drift-point; at minimum according to Section 5.2.5 and the
referenced table 5.2.5.1 on cyclic variation limits, your 2-degree
drift-point is okay from an ASHRAE 55 perspective, assuming your units
are I-P units and not SI units. If you're looking at temperatures in
degrees-C, your drift-point would be 1.1-degree. Is there a different
section you're interpreting the 1-degree drift-point requirement?
On the second question, my read has always been that ASHRAE 90.1-2007
Table G3.1(1)(a) requires ("shall") that your proposed energy model "be
consistent with the design documents, including...HVAC system types,
sizes, and controls;..." So if your project is attempting EQc7.1 and
claiming thermal comfort as demonstrated by compliance with ASHRAE 55
that claim says your design meets the requirements of that standard. In
doing so, your energy model must account for the same control as
documented in the design documents and it would be inferred that this
includes drift points and other design specifications used to confirm
compliance with ASHRAE 55.
Just my personal take - hope it helps!
Jeremy R. Poling, PE, LEED AP+BDC