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RE: [EnergyPlus_Support] air infiltration questions





ASHRAE 62.2 2007 requires homes have supplemental fresh air ventilation.  The number of bedrooms plus 1 = occupants.  The number of occupants X 7.5 CFM, plus 1% of the area.  A 4 bedroom home with 1350 sq ft. would require (5 X 7.5 CFM)+ (1% of 1350)  = 37.5 + 13.5 or 51 CFM.  This is not supposed to include infiltration.  The bathroom &  kitchen exhausts must also vent to the outdoors. 

 

I love runtime vents as a builder in a hot & humid climate.  Because it helps prevent negative pressure, air goes through the filter & the coils and then is distributed through to the ducts.  The Builder’s Challenge program requires this ASHRAE 62.2 ventilation before awarding the certification of Energy Smart with new homes.  First healthy, durable, and then energy efficient. 

 

Why don’t more Mechanical Engineers provide ACCA manual J & D calcs.  Sizing is so important in thermal comfort and efficiency.

 

 

From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of Edward G. Lyon
Sent: Monday, March 08, 2010 10:28 AM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: RE: [EnergyPlus_Support] air infiltration questions

 

 

Very tight houses often have problems with indoor air quality and may have ACH .1 or less.  General US practice targets about .35 ACH as adequate for ventilation without any other provisions, but you should consider your volume to occupancy ratio and recommended minimum ventilation per occupant.  This is a application that typically requires a dedicated ventilation design.

 

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

SIMPSON GUMPERTZ & HEGER
781.907.9000 main
781.907.9350 direct 
781.907.9009 fax
www.sgh.com

 

From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx] On Behalf Of ylinenergy
Sent: Monday, March 08, 2010 9:06 AM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] air infiltration questions

 

 

Hello,

I wonder if anyone can help me with my Energy+ model.

I modelled a small low energy bungalow house in the UK climate with floor area around 100m2. The building fabric has very high performance (U value <0.13). There are totally three zones in the model. I put ideal loads system in the model, and the setpoints for heating is 19C. The results I got it much higher than I expected. It is around 350kwh/m2 for heating loads. I think I must have done something wrong in the model.

I put 0.25ac/h as design flow rate in the Zone infiltration section. I assumed 0.25ac/h is reasonable value for an air tight house. However, if I changed the figure to 0.5, the heating loads jumped to 780kwh/m2. If I changed the figure to 0, the heating loads is just 26kwh/m2. Can anyone suggest the reasonable ac/h value for a well air tight house? I assumed the input figures in Design Flow rate here is the infiltration rate through air leakage and not consider the natural ventilation. Is that right?

I did free running the model, and the average indoor temperature is about 10C, more less the right value, I think.

Can anybody suggest what might be wrong here?

Many thanks in advance.

Best Regards,
Yuan



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