[Greenbuilding] PHPP Flow Rates

Tue Mar 5 19:20:29 CST 2013

This came up in the course of PHIUS's evaluation of a current project.  The
following comment is from Lisa White, Certification Manager:

"The max [PH] Design Air Flow rate is determined by the highest of either
extract requirements by room, supply air requirements by people, or a
volumetric requirement"

Alan Abrams*
**certifed professional building designer, AIBD
certified passive house consultant, PHIUS*
*certified passive house builder, PHIUS**
*Abrams Design Build LLC
*sustainable design for intentional living*
6411 Orchard Avenue Suite 102
Takoma Park, MD 20912
office  301-270-NET- ZERO (301-270-6380)
fax      301-270-1466
cell     202-437-8583
alan at abramsdesignbuild.com
www.abramsdesignbuild.com

On Tue, Mar 5, 2013 at 3:20 PM, JOHN SALMEN <terrain at shaw.ca> wrote:

> Agree on ashrae Canadian standard uses rooms which can have the result of
> over equipping small houses
>
> Sent from my BlackBerry 10 smartphone.
>   *From: *John Straube
> *Sent: *Tuesday, March 5, 2013 10:35 PM
> *To: *Green Building
> *Reply To: *Green Building
> *Cc: *Joe Lstiburek
> *Subject: *Re: [Greenbuilding] PHPP Flow Rates
>
> I think the PHPP approach is a bit of a throwback to the old days when
> people measured required ventilation by ACH.
> A more sensible approach, and the one used by the most common north
> American standard ASHRAE 62, is to assess the need for ventilation based on
> the number of people (since they produce pollutants) and the square footage
> served (since building pollutants, including cleaning supplies etc are
> roughly square foot based).
> A good approach is 7.5 cfm per person plus 0.01 cfm/Square foot. Real
> simple, time tested, logical.
> So for a 1500 sq ft 3 BR home, that would be assumed to be 4 people, and
> hence 30 cfm. Then there is the 15 cfm added for the 1500 sf of building to
> get 45 cfm. This is continous operation. A 90 ccm HRV would be set to run
> 30 minutes on the hour to achieve this.
> We often install more capacity than this (hence your paraphrase of Joe's),
> but commission it at these rates in tight houses (and lower rates in leaky
> production houses), thereby allowing for a higher rate to set if the
> occupancy demands it.
> Recently, the ventilation rates in 62.2 have increased, and these are not
> in my opinion justified IF you do a good job of mixing and filtering
> incoming air. IF you do a bad job of mixing and don't exhaust large
> concentrations of pollutants (kitchen range hoods, bathrooms etc) then you
> would need to increase the baseline rate. But that is bad design and should
> not IMO be recommended.
>
> Many people want to increase the ventilation rate despite the initial cost
> and operating cost penalty to improve indoor air quality. While there is
> some logic to this, it is usually better from a health, economics, and
> environmental point of view to manage the production of indoor pollution
> through material choices and sensible operation than try to solve pollution
> with lots of dilution.
>
> my 2 cents worth
> John
>
> On 2013-03-05, at 1:13 PM, John Salmen <terrain at shaw.ca>
> wrote:
>
> > Maximum flow rate is generally the maximum of your supply and exhaust
> > requirements (based on occupancy, assumed volumes, leakage, etc.) As I
> > understand it PHPP however calculates this just as volume (interior
> building
> > volume) multiplied by .3 ACH (air changes/hour) multiplied by 1.3 (real
> > world factor?). So oversizing by 1.5 keeps it in the real world and
> ensures
> > adequate ventilation.
> >
> > -----Original Message-----
> > From: Greenbuilding [mailto:
> greenbuilding-bounces at lists.bioenergylists.org]
> > On Behalf Of Bob klahn
> > Sent: March-04-13 7:21 PM
> > To: Green Building
> > Subject: Re: [Greenbuilding] PHPP Flow Rates
> >
> > Eli,
> > I can't answer your question directly. I am dealing with a situation
> where
> > I'm pretty sure the ERV flow is low and am equally frustrated.
> > However, I recall a recent posting by Joe Lstiburek saying that they
> > oversized ERV's by 150%.
> >
> > Given what my memory has done to me lately, you might want to find that
> > posting for the rest of the story. Check the BSC site.
> >
> > I hope the lead helps. This thread should be interesting.
> > Bob
> > On 3/4/2013 4:38 PM, Eli Talking wrote:
> >> I am trying to make sense of Ultimate Air spreadsheet describing how
> >> to size ERV flow rates. It references the Ventilation maximum flow
> >> rate as determined from PHPP.
> >>
> >> Does anybody know how to find Ventilation maximum flow rate PHPP?
> >>
> >> Eli
> >>
> >>
> >> _______________________________________________
> >> Greenbuilding mailing list
> >> to Send a Message to the list, use the email address
> >> Greenbuilding at bioenergylists.org
> >>
> >> to UNSUBSCRIBE or Change your List Settings use the web page
> >> http://lists.bioenergylists.org/mailman/listinfo/greenbuilding_lists.b
> >> ioenergylists.org
> >>
> >
> >
> > _______________________________________________
> > Greenbuilding mailing list
> > to Send a Message to the list, use the email address
> > Greenbuilding at bioenergylists.org
> >
> > to UNSUBSCRIBE or Change your List Settings use the web page
> >
> http://lists.bioenergylists.org/mailman/listinfo/greenbuilding_lists.bioener
> > gylists.org
> >
> >
> > _______________________________________________
> > Greenbuilding mailing list
> > to Send a Message to the list, use the email address
> > Greenbuilding at bioenergylists.org
> >
> > to UNSUBSCRIBE or Change your List Settings use the web page
> >
> http://lists.bioenergylists.org/mailman/listinfo/greenbuilding_lists.bioenergylists.org
>
> Prof. John F Straube, P.Eng.
> www.BuildingScience.com
>
>
>
>
> _______________________________________________
> Greenbuilding mailing list
> to Send a Message to the list, use the email address
> Greenbuilding at bioenergylists.org
>
> to UNSUBSCRIBE or Change your List Settings use the web page
>
> http://lists.bioenergylists.org/mailman/listinfo/greenbuilding_lists.bioenergylists.org
>
> _______________________________________________
> Greenbuilding mailing list
> to Send a Message to the list, use the email address
> Greenbuilding at bioenergylists.org
>
> to UNSUBSCRIBE or Change your List Settings use the web page
>
> http://lists.bioenergylists.org/mailman/listinfo/greenbuilding_lists.bioenergylists.org
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.bioenergylists.org/pipermail/greenbuilding_lists.bioenergylists.org/attachments/20130305/c3f70c98/attachment.html>