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RE: [EnergyPlus_Support] Infiltration

Thanks, we have Design Builder in the company, but I don?t use it myself.  When I have some time I?ll check out what they do exactly.

Ned Lyon, P.E. (MA, WV)
Staff Consultant

781.907.9000 main
781.907.9350 direct 
781.907.9009 fax

From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of Jeremiah Crossett
Sent: Friday, February 01, 2013 1:34 PM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: Re: [EnergyPlus_Support] Infiltration

I agree with Ned, but also think it is worth mentioning that Design Builder has a simple input from blower door to Energy Plus that might be worth looking into, and I have attached a screen shot of the input. I am not 100% sure how DB applies this to its E+ file generation but assume it uses the ZoneInfiltrationDesignFlowRate Object pasted from another file below. I think there is a better way to do it with airflow network as well. 

Name Infiltration

Zone or ZoneList Name     Zone

Schedule Name       On

Design Flow Rate Calculation Method     Flow/zone

Design Flow Rate    0.018

Flow per Zone Floor Area 

Flow per Exterior Surface Area    

Air Changes per Hour       

Constant Term Coefficient  1

Temperature Term Coefficient     0

Velocity Term Coefficient   0

Velocity Squared Term Coefficient          0

Jeremiah D. Crossett  | Senior Analyst  |  Phase Change Energy Solutions

120 E. Pritchard St.  | Asheboro, NC 27203  | Mobile 503-688-8951



On Fri, Feb 1, 2013 at 10:15 AM, Edward G. Lyon <<mailto:eglyon@xxxxxxx>eglyon@xxxxxxx> wrote:

In my opinion, the answer to your question is very complex.  I am not sure what you mean precisely by 50Pa test.  Usually this means ACH50 (air changes per hour at 50 Pa), but you could have a complete test that reports Coef and Expon for the flow equation Flow = Coef*Pressure^Expon.

In either case there is no short cut way I see to put this data directly into EnergyPlus.

I also think different procedures may apply to different types of buildings.  If you have a small house, and ACH50 result divided by 20 (sometimes other factors) is a fair approximation of the infiltration air exchange rate for a small building.  You could define Infiltration as an ACH and juggle the coefficients to give you a better guess for seasonal temperature and wind conditions.  Or you could study the research on ACH50 correlations to infiltration and schedule something appropriate for your location.  If you have a commercial building, your test data should be unit area based and you would use Infiltration with a surface area calculation.

Infiltration in EnergyPlus has a sophisticated set of input parameters intended to vary infiltration by site conditions, and I have done a lot of whole building testing.  Perhaps others can provide a good reference for integrating measured data into the energy model, but I have not seen it.  I think there may a way to approximate the pressure from the temperature and wind in order to recalculate coefficients for Infiltration in EnergyPlus.  Perhaps I need to study this in more depth myself.