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

Nick Caton ncaton at smithboucher.com
Tue Aug 16 07:10:54 PDT 2011


Hi Robert,

 

I can only speculate towards the circumstances of the DOE 'tests' you are referring to, but a contributing factor is likely that statements such as: "XXX  CFM/SF reduction of infiltration will result in YYY% energy consumption savings" are inherently case-specific.  Any set of numbers may be true for a specific model of a specific size and type of building in a specific climate (the variables go on and on), but as soon as you change any of number of contributing variables you open the door for the impact of infiltration to change.  

 

This is analogous to the application of the Passivhaus and similar standards to buildings in completely different building types or climates than those the standards are built around.  Someone trying to design/build a Passivhaus home in the Arizona is to some extent missing the point, for example, and will hopefully realize the annual 15kWh/m^2 heating/cooling mandate is itself intended for a specific part of the world.

 

Again, this is as speculative as it must be, but if you're implying DOE models calculate infiltration loads differently than something else, you'll need to first provide more specifics regarding what the 3% number is based on, and ensure the contributing variables to infiltration impact are being held constant against the measurements/model producing the 3% figure...  I think you'll find eQuest/DOE2 models are capable of determining and modeling infiltration in a variety of calculation methods (among which you can mandate a specific ACH or CFM/SF of wall - both convertible from 10m³ /h.m² of wall area), and can also be scheduled to impose any desired hourly level of infiltration upon a model's zones if that's desired.

 

Best of luck,


~Nick

 

 

 

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 Bobby Sy
Sent: Tuesday, August 16, 2011 6:04 AM
To: Eurek, John S NWO
Cc: equest-users at lists.onebuilding.org
Subject: Re: [Equest-users] Basic stuff - Infiltration (UNCLASSIFIED)

 

Hi all,

 

In the UK when modeling houses, for example, the reduction in infiltration provides a much bigger return on the overall energy saving - albeit with a much simpler model engine.  Let me explain.

 

British Building Regulations demand a maximum infiltration rate of 10m³ /h.m² of wall area (at 50pa) - equivalent to a little over a hole the size of a 5 peso coin per m².  Reducing the infiltration rate to 3m³ gets an instant improvement in overall energy consumption of around 3%.  Further, Germany's Passivhaus criteria has a maximum heating demand of 15kWh/m².yr - ditto cooling demand.   To achieve that they regularly build to infiltration not exceeding 1m³.  That's difficult to achieve but the point is I don't see anywhere near the percentage improvements from similar 'tests' with infiltration with the DOE models.  Why is that?

 

Thanks in advance!

 

-Robert

 

On Thu, Aug 11, 2011 at 2:04 AM, Eurek, John S NWO <John.S.Eurek at usace.army.mil> wrote:

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>  <tel:%28206%29%20770-7779>
       Fx: (206) 770-5941 <tel:%28206%29%20770-5941>  <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: 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 <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:

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



       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>  <tel:%28206%29%20770-7779>
       Fx: (206) 770-5941 <tel:%28206%29%20770-5941>  <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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