[Equest-users] Modeling Infiltration and Windows

[Alex Krickx]

Hi all,

Thanks to Pasha and Nick for their input.  It's always good to know that someone else is doing the same thing! Most of the data I have on windows leakage rates is in CFM/ft² and as I don't have information on most of the wall infiltration values on projects I work on (I usually do feasibility studies on existing buildings) I just leave it at the eQUEST default (usually 0.038). Does that sound like an acceptable way of doing it?

Thanks,
Alex


From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Pasha Korber-Gonzalez
Sent: Monday, March 08, 2010 8:47 PM
To: steve clark
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Modeling Infiltration and Windows

A good rule-of-thumb assumption for any new construction is ACH=0.20.  I believe this is based on an ASHRAE reference.  For existing building construction it can be slightly higher than that up to significantly higher depending on the construction type and age of the building.

Generally for new construction 0.20 is a good solid assumption.

pk
On Mon, Mar 8, 2010 at 6:06 PM, steve clark <scstevemclark at gmail.com<mailto:scstevemclark at gmail.com>> wrote:
Hi Nick,

Do you have a reference for the ASHRAE ACH estiamtes you mentioned?

thanks!
Steve
On Mon, Mar 8, 2010 at 7:47 PM, Nick Caton <ncaton at smithboucher.com<mailto:ncaton at smithboucher.com>> wrote:
I've done exactly that in the past for the exactly the same purpose!

The only difference is I believe I always punch in the differences in the metric of ACH.  ASHRAE fundamentals provides some guidance regarding air change rates to expect for various classes of construction as a function of outdoor design temperature, and that was the best I could base my existing construction off of from what info I had available.

Come up with a  "leakiness" for both you construction, old and new windows, and do the weighted average jig =).

Kudos on your fancy facade spelling also ;)!

~Nick
Error! Filename not specified.

NICK CATON, E.I.T.
PROJECT ENGINEER
25501 west valley parkway
olathe ks 66061
direct 913 344.0036
fax 913 345.0617
Check out our new web-site @ www.smithboucher.com<http://www.smithboucher.com/>

From: equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org> [mailto:equest-users-bounces at lists.onebuilding.org<mailto:equest-users-bounces at lists.onebuilding.org>] On Behalf Of Alex Krickx
Sent: Monday, March 08, 2010 6:05 PM
To: equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>
Subject: [Equest-users] Modeling Infiltration and Windows

Hello all,

I am interested in modeling the energy savings that occurs when windows are replaced with lower-infiltration alternatives. In the wizard mode, the only place that I see infiltration is under the "Building Envelope Constructions"  Screen.

I'm hoping someone can confirm my methodology:

Can I input a weighted average of window and wall air infiltration here?  If I'm looking at a building with 20% Window to Wall Ratio, and the windows have 0.1 CFM/ft² while the walls have 0.04 CFM/ft²can I apply an area weighted average into this box? I would take (20%*0.1+80%*0.04) as the façade infiltration value.

That way I could use the same formula to determine the area weighted infiltration of the façade if better windows were installed.

How do other people model this?

Thanks in advance!

Alex Krickx


Alex Krickx
Building Energy Specialist
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1250 Elko Dr, Sunnyvale, CA 94089
(t) 408.541.8124

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