[Bldg-sim] Building Infiltration

[C. J. Gann]

Here's my take on it. The baseline building envelope on a renovation is
supposed to be modeled in the pre-renovated condition. This would include
wall and window thermal properties (U, SHGC, etc.) as well as infiltration
estimates. The proposed design would incorporate all changes and
improvements to the envelope and be modeled as such. It should be noted
however that Section 5.4.3 of 90.1-2004 contains mandatory provisions for
air leakage so the proposed design must at least meet the mandatory
requirements.
 
It is unrealistic to assume a positive pressurization strategy eliminates
infiltration. Keep in mind infiltration occurs due to the vapor pressure and
air pressure differences across the envelope. During unoccupied periods fans
usually do not run so a positive pressurization strategy will not work if
fans are off. During the evenings and weekends the vapor pressure will
equalize from inside to outside bringing in any vapor in this air. Blower
door tests are not practical for most commercial buildings due to the large
volume of air movement required to create a pressure differential. Central
AHU supply and exhaust fans could be used with DDC controls to measure air
leakage provided flow measuring instrumentation was installed.
 
Regards,

Craig J. Gann, P.E.
 

-----Original Message-----
From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Todd Lagus
Sent: Tuesday, March 10, 2009 9:45 AM
To: Karen Walkerman; Mark Prince
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Building Infiltration



While I agree that there is oversight in not giving credit to reduce
infiltration, I do not feel like LEED credit should be given if there isn't
an established baseline.  Say, for example, the building infiltration was
exceptionally poor.  Improving the building to even average infiltration
performance may have a large effect on the energy model, and LEED points
would be given for a building that may or may not deserve it.  While
improving the infiltration issue saves energy for the owner, there is no
guarantee that the building does not perform poorly.  Maybe there should be
a LEED "most improved" award which uses existing conditions as the baseline.

 

Todd Lagus, EIT

Mechanical Engineer

Sebesta Blomberg 
sebesta.com | P  651.634.7236 | F  651.634.7400

 

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From: bldg-sim-bounces at lists.onebuilding.org
[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Karen Walkerman
Sent: Tuesday, March 10, 2009 9:33 AM
To: Mark Prince
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Building Infiltration

 

There aren't any.  There are a few standards that have infiltration
baselines.  I believe the HERS (Home Energy Rating System) uses an
infiltration baseline of about 0.35-0.4 ACH, and there are some other
standards out there.  Of course, some people will argue that the building
should be positively pressurized so that there will be no infiltration.  I
don't know of anyone that has gotten credit for LEED EA C1 for infiltration,
but in my opinion, this is a huge Appendix G oversight.  My suggestion is to
apply for a CIR and suggest an infiltration baseline.  If the building is
100% renovation, the baseline could be established using a blower door test
on the original building, or you could come up with another reasonable,
established baseline.

--
Karen

On Tue, Mar 10, 2009 at 10:16 AM, Mark Prince <mprince at aeieng.com> wrote:

Hello,

I'm involved with a project that is considering pursuing LEED certification.
It is a remodel/renovation of an existing office building.

The existing office building has quite a bit of infiltration.  As part of
the renovation process, the exterior walls are being sprayed with a foam
insulation that will significantly reduce this infiltration.  Someone has
asked the question, if we can take credit for this reduction in
infiltration.  In other words, they want to model the Appendix G baseline
building with the old infiltration rate and model the proposed building with
the new infiltration rate.  This will show a good amount of energy cost
savings.

Is this acceptable?  I'm having a difficult time finding any reference to
infiltration rates within Appendix G.

Thanks,

Mark Prince
Affiliated Engineers
5802 Research Park Blvd.
Madison, WI 53719
(608) 441-6668
mprince at aeieng.com

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