[Bldg-sim] Building Infiltration

Talbert, Joshua jtalbert at hallam-ics.com
Thu Mar 12 12:32:47 PDT 2009


Good Afternoon Mark et al:

I agree with Karen that the infiltration modeling requirements of baseline and proposed are very poorly defined in App G or ECB, and there's no real data in 90.1 section 5.4.3.  A few years back I saw a study on average commercial construction infiltration rates and the general result was ACHs of 0.3 to 0.4.  ASHRAE Fundamentals 05 Ch27.23, discusses commercial building infiltration and lists test results with a range from 0.1 to 1 ACH.  I typically use the same infiltration rate between baseline and proposed when modeling for LEED, UNLESS I have defendable information in the Construction Documents to corroborate a different rate.  For example I had a project whose specs called for blower door testing to prove that overall infiltration did not exceed 0.2 ACH and for the basline I modeled 0.4 ACH, in that job my proposed showed energy improvement via infiltration management as I was able to defend the descrepancy between proposed and basline.

Unless you can defend the difference between the two models I would recommend modeling the same rates.  A blower door test on the original existing building compared to one done on the finished renovations would give you all the defense you need.  One performed just on the new building if it proves the actual rate to be much less then the 0.4 ACH average, in my opinion would probably be defendable enough.

Good Luck,
Josh

Joshua W. Talbert P.E., LEED-AP
Mechanical Engineer
Hallam///ICS
38 Eastwood Dr. Suite 200
S. Burlington, VT 05403
P: (802) 658-4891
F: (802) 658-1457



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


Joshua W. Talbert
Mechanical Engineer
P.E., LEED-AP
Hallam///ICS
38 Eastwood Dr. Suite 200
S. Burlington, VT 05403
P: (802) 658-4891
F: (802) 658-1457





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