[Equest-users] [Bldg-sim] Vestibule Modeling

[Nick Caton]

I concur with the advice to read the requirements more carefully – in almost no case is a vestibule required at every door, when they are required.

Take care and recognize that an Appendix G model is NOT a method to show code compliance.  It’s a procedure for benchmarking the building performance for design which exceeds the minimum requirements of the standard.  The first sections of Appendix G provide a concise overview.

You can evaluate the effect a vestibule or not as already discussed – in function this should simply reduce scheduled infiltration.  That said, I do not believe any Appendix G model should have the proposed and baseline models differing with respect to having a vestibule.  I think table G3.1 is pretty clear that the baseline model is to match the proposed with respect to space/thermal block configuration and arrangement.

Finally, just to drive an extra wedge into the commentary – while the specified mandatory sections (#.4…) ARE required of the design for a LEED project, to pass EAp2, in my humble opinion it’s incorrect (or at least a stretch) to say LEED requires demonstrating compliance with 90.1.

In sum, to the extent vestibules are required (review the sections and exceptions carefully), a LEED project must by design include them in the proposed design.  In turn, the proposed model should incorporate the vestibule in the form of a distinct thermal block (zone/space), to match the actual design.  In turn, the same edits should be applied to the baseline model as it’s supposed to match the proposed model in this regard.

If the vestibules will be designed to be conditioned by the same systems handling the surrounding spaces, you might make the case that it’s a reasonable thing to not model them explicitly as a separated space (modeler has the prerogative to identify and assert where such spatial approximations are appropriate), but in preliminary LEED submission I’d advise making that decision and case clear to the reviewer in your documentation so if it isn’t acceptable you have the opportunity to make the corrections per above prior to final submission.

~Nick

[cid:489575314 at 22072009-0ABB]

NICK CATON, P.E.
SENIOR ENGINEER

Smith & Boucher Engineers
25501 west valley parkway, suite 200
olathe, ks 66061
direct 913.344.0036
fax 913.345.0617
www.smithboucher.com

From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Jim Dirkes
Sent: Tuesday, July 30, 2013 10:25 AM
To: 'RobertWichert'; 'bldg-sim at lists.onebuilding.org'; 'equest-users at lists.onebuilding.org'
Subject: Re: [Bldg-sim] Vestibule Modeling

Robert,
Did you notice the 7 exceptions to section 5.4.3.4?  One of them may apply to you…
As far as modeling goes, a vestibule is principally an infiltration control technique, so I suppose that you could argue for reduced infiltration when vestibules are present.  I am unaware of any research or other information about how they may affect infiltration.  Since infiltration is such a guessing game, I never apply any special curves for vestibules.
p.s., the IECC 2012 (Int’l Energy Conservation Code) includes mandatory envelope and infiltration testing and criteria.  This will probably be a game changer for the construction industry in areas that adopt this code and will definitely affect the energy models prepared for those projects.

James V Dirkes II, PE, BEMP, LEED AP
www.buildingperformanceteam.com<http://www.buildingperformanceteam.com/>
Energy Analysis, Commissioning & Training Services
1631 Acacia Drive, Grand Rapids, MI 49504 USA
616 450 8653

From: bldg-sim-bounces at lists.onebuilding.org<mailto:bldg-sim-bounces at lists.onebuilding.org> [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Rosenberg, Michael I
Sent: Tuesday, July 30, 2013 11:16 AM
To: 'RobertWichert'; 'bldg-sim at lists.onebuilding.org'; 'equest-users at lists.onebuilding.org'
Subject: Re: [Bldg-sim] Vestibule Modeling

Any of the mandatory requirements in Standard 90.1 must be included in your building design and cannot be traded off using a performance approach.



____

______________________

Michael Rosenberg, CEM, LEED AP
Senior Research Scientist
ENERGY & ENVIRONMENT DIRECTORATE

Pacific Northwest National Laboratory
2032 Todd Street
Eugene, OR 97405
(541) 844-1960
michael.rosenberg at pnnl.gov<mailto:michael.rosenberg at pnnl.gov>
www.pnnl.gov<http://www.pnnl.gov>



-----Original Message-----
From: RobertWichert [robert at wichert.org<mailto:robert at wichert.org>]
Sent: Tuesday, July 30, 2013 08:08 AM Pacific Standard Time
To: bldg-sim at lists.onebuilding.org<mailto:bldg-sim at lists.onebuilding.org>; equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>
Subject: [Bldg-sim] Vestibule Modeling


I see that ASHRAE 90.1 requires a vestibule in most cases, but I don't
know if it is modeled or if it is just mandatory.  It would seem to me
that if it was modeled, showing compliance using modeling, without a
vestibule, would be OK (you would make it up somewhere else in the
envelope).  Does anybody know if the vestibule is modeled anywhere, and
how to take it out or put it in?

Since LEED requires compliance with ASHRAE 90.1 Mandatory measures, this
makes a vestibule a mandatory requirement unless I can model it with and
without.  If this is even possible.

Otherwise we must put in a vestibule to comply with LEED.


Is this correct?  Does anybody have other thoughts or ideas?  We have a
very efficient building, modeled without the vestibule in Climate Zone
3B.  I would think that we could take a heating penalty and not install
a vestibule AT EVERY DOOR.


I appreciate your thinking about this.



--
Robert Wichert P.Eng. LEED AP BD&C
+1 916 966 9060
FAX +1 916 966 9068







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