[Equest-users] Basic stuff - Infiltration (UNCLASSIFIED)

Demba Ndiaye Demba.Ndiaye at setty.com
Thu Aug 11 05:08:50 PDT 2011


Infiltration in non-residential buildings is for sure a big concern.



For example, a common assumption is that building pressurization keeps infiltration out (fortunately, John you keep some minimum rate). And it is very tempting to make this assumption of zero infiltration. However, this is not always the case, if we believe Kaplan and Caner ("Guidelines for Energy Simulation of Commercial Buildings", Prepared for Bonneville Power Administration, March 1992, p41):



"The assumption of zero infiltration during hours of HVAC system operation rests on the assumption that system operation will result in building pressurization. However, this presumes a well-designed, well-balanced, and properly operated air distribution system. It also presumes the absence of other infiltration-related effects such as tall building stack-effect, a high frequency of occupant or customer entry and egress, normally-open loading docks, and so forth."



A major factor is the difficulty to obtain and maintain uniform pressurization.



There is certainly a need for a lot more research on the topic of infiltration in non-residential buildings. A closely related topic would relate to the science of air distribution: development of guidelines for uniform pressurization.



At this point, let's make ourselves the favor not to forget this sensitivity analysis on infiltration rates to render the model more robust.



_______________
Demba NDIAYE



-----Original Message-----
From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Eurek, John S NWO
Sent: Wednesday, August 10, 2011 2:05 PM
To: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Basic stuff - Infiltration (UNCLASSIFIED)



Classification: UNCLASSIFIED

Caveats: NONE





Another infiltration issue to consider is the infiltration schedule.  Most of

my designs include building pressurization during occupied hours.  I make an

infiltration schedule and set the infiltration to 10% during occupied hours.



The biggest advantage is that all the outside air goes through an energy

recovery unit and therefore is tempered.







"Is Freedom a small price to pay to stop Global Warming?"



John Eurek PE, LEED AP





-----Original Message-----

From: equest-users-bounces at lists.onebuilding.org

[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Robby Oylear

Sent: Wednesday, August 10, 2011 11:55 AM

To: Mehta, Gaurav

Cc: equest-users at lists.onebuilding.org

Subject: Re: [Equest-users] Basic stuff - Infiltration



Gaurav's screenshot didn't come through for me, so to summarize, in order to

take wind-speed correction factors into account you need to take the value of

INF-FLOW/AREA that the wizard inputs into the detailed file and convert it to

an AIR-CHANGE/HR value.  eQUEST does not apply wind-speed correction to

INF-FLOW/AREA (see below).



>From DOE-2 help file on INF-METHOD:



AIR-CHANGE



The infiltration rate is calculated using the air-change method.

AIR-CHANGES/HR or INF-FLOW/AREA should be specified if INF-METHOD =

AIR-CHANGE. In this case the value AIR-CHANGES/HR will be corrected for wind

speed each hour, but the value of INF-FLOW/AREA will not be corrected. If

both AIR-CHANGES/HR and INF-FLOW/AREA are specified, the resulting

infiltration rates are added.





On Wed, Aug 10, 2011 at 9:50 AM, Mehta, Gaurav <Gaurav.Mehta at stantec.com>

wrote:





      Here is a recent response that I posted on Bldg-Sim.







      Gaurav Mehta, LEED® AP BD+C

      Sustainable Building Analyst

      Stantec



      1932 First Avenue Suite 307

      Seattle WA 98101

      Ph: (206) 770-7779 <tel:%28206%29%20770-7779>

      Fx: (206) 770-5941 <tel:%28206%29%20770-5941>

      Gaurav.Mehta at stantec.com



      stantec.com <http://www.stantec.com>







      The content of this email is the confidential property of Stantec and

should not be copied, modified, retransmitted, or used for any purpose except

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      From: equest-users-bounces at lists.onebuilding.org

[mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Nick Caton

      Sent: Wednesday, August 10, 2011 9:40 AM

      To: Robby Oylear; John Bixler

      Cc: equest-users at lists.onebuilding.org





      Subject: Re: [Equest-users] Basic stuff - Infiltration











      Robby - awesome post, thanks for linking that paper!







      As an extra heads up/thought:  depending on which infiltration method

is selected, I do believe eQuest will also calculate hourly infiltration

rates working from windspeed in the weather file.  Details would be in the

help files...  I can't recall if this happens with the default method, or if

there is a single "default" method (it might vary based on how you define

infiltration at the wizard level?)...







      ~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 <http://www.smithboucher.com>







      From: Robby Oylear [mailto:robbyoylear at gmail.com]

      Sent: Wednesday, August 10, 2011 11:28 AM

      To: John Bixler

      Cc: Nick Caton; equest-users at lists.onebuilding.org

      Subject: Re: [Equest-users] Basic stuff - Infiltration







      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.p

df) 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:



      Error! Filename not specified.



      Error! Filename not specified.







      Error! Filename not specified.







      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 <http://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







      Error! Filename not specified.







      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 <http://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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      ---------- Forwarded message ----------

      From: "Mehta, Gaurav" <Gaurav.Mehta at stantec.com>

      To: "bldg-sim at lists.onebuilding.org" <bldg-sim at lists.onebuilding.org>

      Date: Tue, 2 Aug 2011 11:12:31 -0600

      Subject: Re: [Bldg-sim] RE : Infiltration effect in Climate 1





      Richard,







      Are you using the default infiltration rate (0.038 cfm/ft2 of

external wall area) for the perimeter spaces?







      eQUEST calculates the cfm based on the external wall area and then

converts this to an infiltration flow (cfm/ft2 of floor area of the space).







      As Fredrick has pointed out this infiltration flow assigned by eQUEST

to each perimeter space is not depended on the climate.







      See the help section screenshot below:



















      It is a flat rate assigned to each space and does not include any

wind speed correction and inside-outside temperature difference. The 0.038

cfm/ft2 (of external wall area) infiltration rate was included in the ASHRAE

Standard 90.1-1989 as a beginning assumption and that's what shows up in

eQUEST as default.







      It is good that you are questioning the effect of infiltration on the

energy use of building that you are modeling. In the absence of blower door

test results it is difficult to imagine the real infiltration rate in a

building as it depends on many factors such as the workmanship of the actual

construction, stack effect, inside-outside temperature difference, wind-speed

and how well the building is pressurized by the HVAC system.







      I'll suggest go through the following study by PNNL: Infiltration

Modeling Guidelines for Commercial Building Energy Analysis

<http://www.pnl.gov/main/publications/external/technical_reports/PNNL-18898.p

df>







      Although the report is Energy Plus specific but it can be applied to

eQUEST as well. In a recent project I used the PNNL guidelines and further

converted the infiltration flow for each space to air-changes per hour to

take the wind-speed correction into account. This method still has limitation

of not taking into account the inside-outside temperature difference (see

above screen-shot). I found the rest of the methods that include both

wind-speed correction and inside-outside temperature difference to be

specific to residential buildings.







      Hope it helps.







      Thanks.







      Best regards,







      Gaurav







      Gaurav Mehta, LEED® AP BD+C

      Sustainable Building Analyst

      Stantec



      1932 First Avenue Suite 307

      Seattle WA 98101

      Ph: (206) 770-7779 <tel:%28206%29%20770-7779>

      Fx: (206) 770-5941 <tel:%28206%29%20770-5941>

      Gaurav.Mehta at stantec.com



      stantec.com <http://www.stantec.com>







      The content of this email is the confidential property of Stantec and

should not be copied, modified, retransmitted, or used for any purpose except

with Stantec's written authorization. If you are not the intended recipient,

please delete all copies and notify us immediately.







      ü Please consider the environment before printing this email.







      From: bldg-sim-bounces at lists.onebuilding.org

[mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Genest, Frederic

      Sent: Monday, August 01, 2011 6:03 PM

      To: ROBERT GOMEZ; bldg-sim at lists.onebuilding.org

      Subject: [Bldg-sim] RE : Infiltration effect in Climate 1











      Hello Richard.



      I'm not used to eQuest, but since it is using DOE in the background,

same as EE4 I'm using more frequently, I'll try to answer correctly.



      Climate Zone has nothing to do with infiltration rates, except when

in comes to wind speed and such. However, I don't think DOE is considering

wind speed when calculating infiltration rates; it is usually defined as a

constant, based on a value such as ACH or cfm/ft.sq. of wall area.



      As such, I would start to check your infiltration inputs to see what

is defined, first in eQuest and then in the DOE input file. I'm pretty sure

you'll find your answer somewhere there.



      Also note that design infiltration rate and "actual, under operating

conditions" infiltration rate, are two different things. The average constant

infiltration rate is adequate enough for the later one.



      Also, if you ever need to model a real infiltration from blower door

test results, I personnaly use the 50 Pa value divided by 20 for actual,

normal operation conditions, while the 75 Pa value would be divided by 35 (in

whatever units those values are provided).



      Regards.







      Frederic Genest, ing., M.Sc.A.

      LEED AP, ASHRAE HBDP

      fgenest at pageaumorel.com



      Pageau Morel et associés

      210 Cremazie Ouest, suite 110

      Montréal, Qc H2P 1C6

      T) 514-382-5150 begin_of_the_skype_highlighting

514-382-5150      end_of_the_skype_highlighting

begin_of_the_skype_highlighting              514-382-5150

end_of_the_skype_highlighting  F)514-384-9872

      www.pageaumorel.com





      -------- Message d'origine--------

      De: ROBERT GOMEZ [mailto:rsg4999 at yahoo.com]

      Date: dim. 31/07/2011 23:05

      À: bldg-sim at lists.onebuilding.org

      Objet : [Bldg-sim] Infiltration effect  in Climate 1



      Hello all,



      I'm currently involved in a project that is located in International

Climate Zone 1 (Very Hot - Humid). The building has no heating system, HVAC

systems are only for cooling. Infiltration effect is smaller than I expected

from the eQuest energy model result. I know it has something to do with the

climate. Can anyone tell me the reason why?



      Thanks in advance!





      Richard Gulli

      Project Engineer





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Classification: UNCLASSIFIED

Caveats: NONE





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