[Equest-users] Modeling Infiltration and Windows

[Pasha Korber-Gonzalez]

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> 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>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
>>
>> [image: cid:489575314 at 22072009-0ABB]**
>>
>> * *
>>
>> *NICK CATON, E.I.T.***
>>
>> PROJECT ENGINEER
>>
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>>
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>>
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>>
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>>
>>
>>
>> *From:* 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
>> *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
>>
>>
>>
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>
>
> --
> Steve Clark, MS PhD RESNET BPI ITC
> ClarkEnergyConsultants.com
> 484.477.7525
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