[Bldg-sim] Air leakage, LEED, and Appendix G of ASHRAE 90.1

Marcus Sheffer sheffer at energyopportunities.com
Mon Aug 24 06:21:59 PDT 2009


As I understand it the issue is that the 90.1 Standard does not establish a
base line condition for air leakage so no savings can be claimed.  I
certainly agree that the savings are real and should be counted.  I know
that the Appendix G committee has this issue on their extensive “to do”
list.

 

Marcus Sheffer, Chair – USGBC EA TAG

7group

 

 

From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Paul Grahovac
Sent: Wednesday, August 19, 2009 7:00 PM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] Air leakage, LEED, and Appendix G of ASHRAE 90.1

 

The National Institute of Standards and Technology (NIST) did an extensive
study documenting a greater than 40% natural gas savings and a greater than
25% electricity savings across the nation for building energy consumption if
buildings were uniformly constructed with air barrier systems installed.
They evaluated 116 existing buildings and computer modeled several different
building types.  The purpose of their study was to provide information to
ASHRAE concerning whether it would be desirable to add an air barrier
requirement to ASHRAE 90.1.

 

As a result, I’ve always thought that Appendix G to ASHRAE 90.1 allows you
to change the air leakage rate off the default and onto a rate corresponding
to an air barrier installation, so that you could claim LEED points for the
corresponding energy savings.  However, an architect at a presentation I did
said you could not do that under the LEED and ASHRAE requirements.  (I know
the models will do it, because I’ve done it on the TRANE model and obtained
results that support the NIST findings.)

 

I see in Appendix G that:  “G3.1.2.5. Ventilation.  Minimum outdoor air
ventilation rates shall be the same for the proposed and baseline building
designs.”  However, I searched the document for “outdoor air ventilation”
and the phrase occurs only in the context of mechanical systems that are
designed to intentionally bring air into the building.  If this section is
the basis for concluding that air leakage barriers should be left out of the
modeling, then I have trouble understanding why.

 

Appendix G says that all components of the building are to be modeled as
designed.  That would preclude modeling as if an air barrier system did not
exist in the design.  It says the baseline building model is to have
steel-framed above-grade walls, and it is silent about the design building,
but the User’s Manual says that if the design building walls are block or
cast concrete, then “the mass is credited in the building performance rating
method.”  Likewise, if the walls are wood stud instead of steel, then the
Manual says credit is given for the superior energy performance of wood
frame versus steel frame.  The User’s Manual states that it:  “Offers
information on the intent and application of Standard 90.1.”  Given these
examples in the Manual based on existing thermal mass energy-saving data and
wood-versus-steel stud energy data, it is difficult to conclude that a wall
that is constructed with materials meeting the air leakage limits and
installation requirements of the Air Barrier Association of America and
determined to produce significant energy savings by the NIST study based on
those same limits and requirements should be modeled as if it leaked air
like a building without an air barrier. 

 

Please let me know what you think, and if you know of any reason why it is
not proper to change the air leakage rate through the building envelope in
the design model to show the benefit of air barriers.

 

Thanks,

 

Paul Grahovac, LEED AP

R-GUARD Air & Water-Resistive Barrier Product Manager

PROSOCO, Inc.

3741 Greenway Circle

Lawrence, Kansas  66046

(785) 830-7355

(888) 376-3417 fax

pgrahovac at prosoco.com

web site  http://www.prosoco.com/

 

 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.onebuilding.org/pipermail/bldg-sim-onebuilding.org/attachments/20090824/56a06f52/attachment-0001.htm>


More information about the Bldg-sim mailing list