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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