[Equest-users] Window replacement and infiltration rate changing

[Carol Gardner]

So maybe we can use what Alex said: new windows must be 3x less leaky than
old ones. Since that is just the window, not the whole exposure leakage, I'd
go ahead and pull a number from the table Alex sent that matched my window,
reduce it by 3 and then do an area weighted average for the entire wall. As
a guide you could use .038 cfm/sf or 0.05 cfm/sf for a wall of the same
exposure as yours and with the same glass area as yours to figure out what
the wall cfm/sf is, unless you happen to know it. As an example xx sf wall x
wall cfm/sf + yy sf window x yy cfm/sf for your window = xx+yy sf x .038
cfm/sf, you know your xx and yy sf, you can pick a reasonable cfm/sf for
your window, or ask Alex for one, and then solve for your wall cfm/sf.
Assuming you aren't doing anything to improve your walls you then have your
xx cfm/sf. Then reduce your yy cfm/sf by a factor of 3, plug all the numbers
in and solve for your new xx+yy, or overall wall cfm/sf. Put that number in
eQUEST, document your calcs for the LEED, or whoever, reviewer and you are
good to go.

Carol

On Wed, Sep 15, 2010 at 4:07 PM, Chris Jones <cj at enersave.ca> wrote:

>  ASHRAE 90.1-1989 prescribed the amount of infiltration to use in the
> design and budget cases as 0.038 cfm/sq. ft. of gross exterior wall area.  I
> believe that subsequent versions of 90.1 dropped any reference to modelling
> infiltration rates.  The infiltration is "on" when the fans are off.
>
> The MNECB/CBIP in Canada uses 0.05 cfm/sq. ft of gross exterior wall area -
> with a schedule on all of the time.
>
> Who knows where those numbers came from and it doesn't really answer the
> question of how much infiltration will be saved with new windows but it
> gives a starting point.
>
>
>
> At 06:16 PM 15/09/2010, Alex Krickx wrote:
>
> Content-Language: en-US
> Content-Type: multipart/related;
>
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>
>
> Yeah, it does sound high, doesn’t it? But when compared to the maximum
> level for new windows of 0.3, then it doesn’t sound as high… new windows
> must be 3x less leaky than old ones – that sounds like the right reduction
> to me.
>
> The only link I could find on performance of old windows was this one:
> http://www.bfrl.nist.gov/IAQanalysis/CONTAM/table00_arld.htm
>
> It gives leakage areas in “area per linear meter of seam”. A colleague
> converted this to leakage area in CFM/SF at 75 pa. His number was 1.4 CFM/SF
> based on the table (not sure which value he used).
>
> As a thought: perhaps 1 CFM/SF seems too high because we imagine it as the
> infiltration for a whole wall, when in actuality it only applies to the
> window? Assuming the wall has little infiltration, a 25% WWR would bring 1
> CFM/SF (window) to around 0.25 CFM/SF (whole façade) – probably a little
> higher if accounting for the wall leakage, but not significantly so. Does
> that number still raise alarm bells? Not to me, but I don’t have as good a
> feel for this as Carol does.
>
> I’ve definitely seen some leaky windows – unfortunately I’ve never tested
> how leaky they are so I’m stuck with looking for industry papers and best
> practice.  I definitely would like to learn more about this though. Typical
> infiltration values of old windows seems to be a big question mark with
> people I’ve asked….
>
> Regards,
> Alex
>
>
> *From:* Carol Gardner [ mailto:cmg750 at gmail.com <cmg750 at gmail.com>]
> *Sent:* Wednesday, September 15, 2010 2:57 PM
> *To:* Alex Krickx
> *Cc:* YingQi Chen; equest-users at lists.onebuilding.org
> *Subject:* Re: [Equest-users] Window replacement and infiltration rate
> changing
>
> Wow! It seems like 1 cfm/sf for infiltration would be a lot. The people's
> hair next to the windows would be blowing all around! That's the average
> number I use for HVAC ventilation.
>
> Carol
> On Wed, Sep 15, 2010 at 2:36 PM, Alex Krickx <akrickx at seriousmaterials.com>
> wrote:
> Hi Yingqi,
>
> I’m pretty sure eQUEST does not automatically adjust infiltration rates.
>
> If you search through the archives and look up “infiltration windows” you
> can find some relevant posts. I’ve attached one email that was sent around
> earlier this year describing one way to change the infiltration between
> current and proposed cases.
>
> I don’t think you can apply a percentage reduction without some more
> information. I believe that the requirement to meet the DOE’s VPP for
> windows is a maximum infiltration of 0.3 CFM/SF – this leads me to believe
> that some new windows have more infiltration than this. My company
> manufacturers windows with infiltrations as low as 0.01 CFM/SF. I’m having a
> hard time finding a source, but I’m pretty sure I’ve heard of modeling
> existing windows with infiltration as high as 1 CFM/SF. A building with a
> large WWR and very leaky windows could substantially reduce whole-building
> infiltration values.
>
> Good luck!
> Alex Krickx
>
>
> Alex Krickx
> Building Energy Specialist
> [image: email_sig]
> 1250 Elko Dr, Sunnyvale, CA 94089
> (t) 408.541.8124
>
> *Warning:* The information contained in this e-mail may be privileged
> attorney-client communications or attorney work product and/or proprietary
> and confidential.  If the reader of this message is not the intended
> recipient then you have received it in error and any review, distribution or
> copying of this message is prohibited and you are to notify us immediately
> by reply e-mail and delete the original message immediately.
>
>
>
> *From:* equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org<equest-users-bounces at lists.onebuilding.org>]
> *On Behalf Of *Carol Gardner
> *Sent:* Wednesday, September 15, 2010 2:19 PM
> *To:* YingQi Chen
> *Cc:* equest-users at lists.onebuilding.org
> *Subject:* Re: [Equest-users] Window replacement and infiltration rate
> changing
>
> If eQUEST changed the infiltration between the two cases you would be able
> to see the change in your .inp deck. I'm not sure what the impact of doing
> the change using the EEM Wizard vs. simply copying and renaming your input
> deck and making the change in it's own .inp deck would be. You could
> experiment and see if there's a difference. If it doesn't change your
> infiltration I would lower the perimeter infiltration rate conservatively by
> a fixed percent. You might Google infiltration rates on line and find some
> information related to how much to expect for a single pane window to a
> double pane window. Also, be sure to account for your frames, too. Are they
> thermally broken? Does the frame material change, etc.
>
> Carol
> On Wed, Sep 15, 2010 at 2:05 PM, YingQi Chen <yingqi.chen at pertan.com >
> wrote:
> Dear eQuester:
>
> I want to run a simulation by EEM wizard. I want to replace exiting single
> pane, clear windows with double pane clear windows for a school building.
>
> I changed the class type form single pane clear to double pane clear
> windows.  The energy saving doesn’t look good.  I have two following
> questions need someone's guidance.
>
> *Question 1:
> *
> My question is that this EEM will reduce perimeter infiltration rate of the
> building. I am not quit sure if I need to reduce the perimeter infiltration
> rate in the simulation. If, it does, how many percentage of infiltration
> rate do I need to reduce?
>
> *Question 2:
> *
> Does eQuest programmer has already considered this issue and changed the
> perimeter infiltration rate automatically with changing window glass type
> and insulation of the windows?
>
> Yingqi Chen
>
> The PERTAN Group
> 44 Main Street, Suite
> Champaign, IL 61820
>
> 217-356-1348 ext 205
>
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>
> --
> Carol Gardner PE
>
>
> ---------- Forwarded message ----------
> From: Nick Caton <ncaton at smithboucher.com >
> To: Alex Krickx < akrickx at seriousmaterials.com>, "equest-users at lists.onebuilding.org"
> < equest-users at lists.onebuilding.org>
> Date: Mon, 8 Mar 2010 16:47:48 -0800
> Subject: RE: [Equest-users] Modeling Infiltration and Windows
> 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
> [image: cid:489575314 at 22072009-0ABB]
> *
> 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*
> *
> *From:* equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org<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
> *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
> [image: email_sig]
> 1250 Elko Dr, Sunnyvale, CA 94089
> (t) 408.541.8124
>
> *Warning:* The information contained in this e-mail may be privileged
> attorney-client communications or attorney work product and/or proprietary
> and confidential.  If the reader of this message is not the intended
> recipient then you have received it in error and any review, distribution or
> copying of this message is prohibited and you are to notify us immediately
> by reply e-mail and delete the original message immediately.
>
>
>
>
>
>
> --
> Carol Gardner PE
>
>
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>
> Chris Jones
> 14 Oneida Avenue
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> Fax. 416-946-1005
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-- 
Carol Gardner PE
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