[Equest-users] Basic stuff - Infiltration

[Robby Oylear]

John,

The infiltration as a function of exterior gross wall area is only available
in the wizard.  I don't believe DOE2.2 is capable of having inputs that
relate to the sum of a parameter of it's child components.  The DOE2.2 BDL
Functions do not have any references to child components (i.e. a Wall can
reference a parameter of its parent Space, but a Space cannot reference a
parameter of its child Wall).

Regarding Lawrence's initial question about converting a known tested value
to a value usable within eQUEST, the PNNL Report 18898, Infiltration
Modeling Guidelines for Commercial Building Energy Analysis (
http://www.pnl.gov/main/publications/external/technical_reports/PNNL-18898.pdf)
contains
formula for converting infiltration from a test case to an actual design
case. Based on the example presented in the document, a conversion factor of
0.112 can be derived.

So a tested air leakage of 0.40 CFM/SF at 0.30 in. w.g. would be modeled at
0.045 CFM/SF.  This value is modeled at 100% when building fan system is off
and 25% when the building fan system is on.

Granted, this may be an oversimplification for eQUEST, as the document was
written for EnergyPlus which contains a wind-driven infiltration model, but
it seems to be a good starting point at least if you have test information
available.

*Robby Oylear, LEED**®** AP BD+C*

*Mechanical Project Engineer*

*Energy Analyst*

* *

*D* 206-788-4571 | *C* 206-354-2721

*www.rushingco.com* <http://www.rushingco.com/>


On Wed, Aug 10, 2011 at 8:17 AM, John Bixler <JBixler at sebesta.com> wrote:

> Thanks for the response Nick.****
>
> ** **
>
> As I recall from a recent foray into this subject in eQuest (in detailed
> mode), the cfm/sq ft entry is based on floor area.****
>
>
> It would be logical that if cfm/sq ft of exterior wall is an option in
> wizard mode, it would also be an option in detailed mode – I just haven’t
> dug that far yet.****
>
> ** **
>
> *From:* Nick Caton [mailto:ncaton at smithboucher.com]
> *Sent:* Wednesday, August 10, 2011 10:08 AM
> *To:* John Bixler; equest-users at lists.onebuilding.org
> *Subject:* RE: [Equest-users] Basic stuff - Infiltration****
>
> ** **
>
> Hi John – thanks for your thoughts!****
>
> ** **
>
> I was relating some of the same concerns with others off-list … I’m am no
> infiltration-auditing expert (though some lurk among us here on the lists
> ^_~), but one thing I can say based on my past attempts to build a better
> mousetrap regarding infiltration is that where ASHRAE may be generally vague
> on the topic – they are actually doing a lot to say (if not always directly)
> that whole building infiltration is a very difficult thing to quantify at
> best (sorry for excessive use of parentheticals (I mean it!)…).****
>
> ** **
>
> The best guidance imaginable that would still be practical in day-to-day
> use would have to rely in some part on subjective observations (guesses)
> regarding envelope constructions.  Two brick walls of certain grout/masonry
> ratios weathered for the same period in the same climate may still have
> different leakiness because the two masons used slightly different grout
> mixes…  What I’m getting at is you couldn’t realistically construct a table
> that covered every variable, and many variables are not “knowable.” ****
>
> ** **
>
> That’s not to say the residential ACH table isn’t useful for subjective
> estimations, nor that research couldn’t be undertaken to raise the bar a
> notch.  As John is alluding, a table providing representative commercial
> envelope constructions (with accompanying illustrations!) and/or layer
> combinations could be undertaken that would provide infiltration performance
> as a function of time.  Values could be given for new construction, and
> after weathering for 1/5/10 years.  While new constructions/layers could be
> assessed in a controlled environment, initial research on aged constructions
> would need to be done sampling within a single climate zone.
> Separate/concurrent research could explore determining multipliers on the
> weathering effects based on varying climate and geography…  All things being
> equal, a beachside wall built in Miami, FL with lots of sun/salt/torrential
> rain seasons and the occasional hurricane will weather differently over a
> decade than the same wall in a milder climate.  The net result of such
> research could ultimately produce some really helpful tools in better
> assessing existing and new constructions for a variety of industries and
> purposes (energy modeling included).****
>
> ** **
>
> Considering the growing presence and pressing need for better tools in the
> world of energy modeling, I would put forward prime candidates for whole
> construction assemblies would be ASHRAE 90.1 baseline constructions as
> defined in Appendix A.  ****
>
> ** **
>
> For all I know, such research may be underway or completed years ago – my
> ear is not quite so close to the ground with the academic world… can anyone
> comment?****
>
> ** **
>
> ** **
>
> To another point you brought up – eQuest is quite capable of using your
> personally developed CFM/ft2 values – in the wizards even!  In detailed mode
> you’ll find there are inputs for more involved estimations as well if you
> wish to pursue other methods:****
>
> ****
>
> ****
>
> ** **
>
> [image: 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:* equest-users-bounces at lists.onebuilding.org [mailto:
> equest-users-bounces at lists.onebuilding.org] *On Behalf Of *John Bixler
> *Sent:* Wednesday, August 10, 2011 9:23 AM
> *To:* equest-users at lists.onebuilding.org
> *Subject:* Re: [Equest-users] Basic stuff - Infiltration****
>
> ** **
>
> My own personal opinion is that ASHRAE Fundamentals has not rescued us
> here.****
>
> ** **
>
> As Nick mentioned, the data presented there is for residential houses and
> relies on incredibly vague and subjective judgment calls by the modeler. *
> ***
>
> ** **
>
> Furthermore, the values presented are in the unit’s of air changes per
> hour.  To me, this is a terrible way to use the data.  Your entries for
> infiltration then rely on the volume of the room to determine the amount of
> infiltration.  The volume of the room (zone is probably a better term) has
> NOTHING to do with the infiltration.  What if I have a gym that’s
> 150’x100’x50’ tall, but it only has 10’ wide by 50’ tall of exterior
> wall???  If I use the ASHRAE method and rely on air changes per hour, the
> zone will be modeled with a HUGE GIGANTIC REALLY REALLY LARGE amount of
> infiltration.  ****
>
> ** **
>
> Yet this seems to be the only recourse we have that is grounded in any sort
> of defendable data.****
>
> ** **
>
> I have looked and looked for a reliable report or other source for real
> world commercial/institutional construction infiltration values to no
> avail.  It would be so incredibly useful.****
>
> ** **
>
> I have, over the course of my energy modeling career, developed a set of
> seemingly practical infiltration values to use, using the units of “CFM per
> sq ft of gross external wall area” available in Trane Trace (I don’t believe
> these units are an option in eQuest).  These values were developed by taking
> a number of buildings with no infiltration and arbitrarily adding
> infiltration in, until I get a reasonable utility consumption value.  Hardly
> scientific and no way could I defend these values if they came under
> scrutiny, other than to say “well, you got a better idea????”****
>
> ** **
>
> Some may say “Eh, who cares about infiltration anyway?”.  Well, it makes a
> bigger difference then you’d think.  ****
>
> ** **
>
> A novice user who relies on the ASHRAE air changes per hour is likely
> significantly oversizing their cooling equipment in large rooms (ie
> conference, assembly, gyms, etc) which is exactly where you don’t want to be
> oversizing cooling equipment.  ****
>
> ** **
>
> Think about the components of a heating load – envelope conduction losses,
> taking in cold OA…and infiltration.  Envelope losses are generally small,
> the design community likes to temper their OA (rightfully so), so where is a
> major component of the heating (consumption) load coming from?  Infiltration
> really adds up.  ****
>
> ** **
>
> How do you justify replacing leaky, wood sash windows?  How bout making a
> switch to spray foam insulation?  How about modeling door seals?  ****
>
> ** **
>
> I’ve rambled enough.  Point being, we all are forced to use arbitrary
> numbers for something that is a significant component of both equipment
> sizing and energy modeling and it just makes me mad and embarrassed when I
> have to explain to a client or colleague “well those are really important,
> but completely imaginary, numbers…”****
>
> ** **
>
> *From:* equest-users-bounces at lists.onebuilding.org [mailto:
> equest-users-bounces at lists.onebuilding.org] *On Behalf Of *Bruce
> Easterbrook
> *Sent:* Tuesday, August 09, 2011 5:41 PM
> *To:* John Bixler
> *Subject:* Re: [Equest-users] Basic stuff - Infiltration****
>
> ** **
>
> Since 1922!
> Bruce Easterbrook P.Eng.
> Abode Engineering
> ASHRAE Member
>
> On 09/08/2011 06:11 PM, lawrence Lile wrote: ****
>
> Good ol ASHRAE Fundamentals!  Why didn't I think of looking there?  Thanks!
>   ****
>
> ** **
>
> ** **
>
> On Mon, Aug 8, 2011 at 11:36 AM, Nick Caton <ncaton at smithboucher.com>
> wrote:****
>
> Hi Lawrence,****
>
>  ****
>
> My copy of ASHRAE Principles of HVAC includes a table (5-1) excerpted from
> ASHRAE Fundamentals, 2001 (Table 7, Ch 28).  This table provides air change
> rates as a function of subjective envelope airtightness (“tight” / “medium”
> / “loose”) and as a function of the outdoor design temperature.  Upon
> reviewing the referenced Fundamentals chapter, I learned this table is built
> from research surveying residential homes of various vintages, so it helps
> to know that these are “tight” to “loose” residential constructions.  ****
>
>  ****
>
> In any case, I’ve used and cited this resource before when modeling
> infiltration and calculating sizing loads for non-residential projects as
> well.  I’ve searched, but have yet to come up with an equivalent table based
> on surveying and measuring commercial constructions from a
> subjective/objective standpoint… That might be handier, but in the meantime
> this is a good tool for “converting” your subjective observations into the
> right ballpark.  ****
>
>  ****
>
> ~Nick****
>
>  ****
>
> [image: 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:* equest-users-bounces at lists.onebuilding.org [mailto:
> equest-users-bounces at lists.onebuilding.org] *On Behalf Of *lawrence Lile
> *Sent:* Sunday, August 07, 2011 12:50 PM****
>
>
> *To:* equest-users at lists.onebuilding.org****
>
> *Subject:* [Equest-users] Basic stuff - Infiltration****
>
>  ****
>
> In building modeling programs one always has to provide precise values for
> infiltration.  In the real world, I will know one of two things:  almost
> nothing (The building appears to be kinda leaky with old windows), or I will
> have a blower door test done at a specific pressure.  How do I convert
> subjective ("kinda leaky") or objective (Blower door test) leakage into
> numbers that make sense in the program?  Is there a guide one can use?  **
> **
>
>  ****
>
>  ****
>
> --Lawrence****
>
> ** **
>
> ** **
>
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