[Bldg-sim] 90.1 and infiltration/air-tightness?

[Michael Tillou]

Nick,

ASHRAE 90.1 doesn't allow any credit for infiltration savings for commercial
buildings and doesn't have any specific guidance about an allowable air
tightness value.  When using Appendix G or Chapter 11 ECB you need to keep
infiltration the same in both the proposed design and the energy budget.  

The IECC and RESNET HERS offer a method for infiltration savings in
Low-Rise/Single Family Residential.  I believe both methods allow a minimum
as-designed infiltration of ACH = 0.35.  The baseline uses weather factors
from ASHRAE 136 and a Normalized Leakage value of 0.57.  The IECC also
requires a post-construction blower door test to verify the savings.

You could probably propose an exception calculation for infiltration credit
if it followed the IECC residential method and the proposed building was a
small building with simple systems.  I certianly don't think it would be
applicable for a large multi-story building with complex systems.   I think
that you would also need to be able to demonstrate the as-built (post
construction) infiltration rate, through blower door testing or other
appropriate means, as part of proposed exception calculation.

Best regards,

Mike



-----Original Message-----
From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Nick Doylend
Sent: Tuesday, February 12, 2008 3:58 PM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] 90.1 and infiltration/air-tightness?

Hi, I'm wondering if 90.1 makes any stipulations regarding building air
infiltration, for example can there be a difference between proposed design
and energy budget building?  I can't seem to find any reference to facade
air tightness but the standard is a pretty dense document to wade though.
Is there a more easily digested summary available anywhere?

Thanks,

Nick
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