Suburban DynaPack A&E Manual 07/2019 Rev.6
37
VENTILATION CALCULATION
‘qvs = Cs x Qv x delta-t
‘qvl = Cl x Qv x delta-w
‘qvt = qvs + qvl
‘qvs = sensible ventilation load, BTU/hr
Cs = air sensible heat factor, 1.1 BTU/hr*cfm*F, at sea level
Cl = air latent heat factor, 4840 BTU/hr*cfm, at sea level
Qv = ventilation flow rate, cfm
Delta-t = indoor/outdoor temperature difference F
Delta-w = indoor/outdoor humidity ratio difference
‘qvl = latent ventilation load, BTU/hr
‘qvt = total ventilation load, BTU/hr
LOAD CALCULATION EXAMPLE
The indoor condition for cooling is 75° F dry bulb with 50% humidity, and a
humidity ratio of 0.0094. The indoor condition for heating is 68° F dry bulb.
The domicile is a 2600 square foot condo with 3 bedrooms in the Chicago
area. From above the minimum ventilation rate is 56 cfm. The sensible heat
load added during cooling due to the ventilation is:
‘qvs = Cs x Qv x delta-t = 1.1 BTU/hr*cfm*F x 56 cfm x (89°F -75°F) =
862 BTU/hr
The latent heat load added during cooling due to the ventilation is:
‘qvl = Cl x Qv x delta-w = 4840 BTU/hr*cfm x 56 cfm x (0.0142- 0.0094) =
1300 BTU/hr
The total heat load added due to ventilation for cooling is 862 + 1300 =
2162 BTU/hr
The sensible heat load added due to ventilation for heating is:
‘qvs = Cs x Qv x delta-t = 1.1 BTU/hr*cfm*F x 56 cfm x (68°F-2.2°F) =
4053 BTU/hr.
TABLE 9
CITY
Dry Bulb/Web Bulb/Humidity Ratio Dry Bulb
SUMMER MAXIMUM
CONDITIONS
WINTER MINIMUM
CONDITIONS
CLIMATE CONDITIONS by CITY
87.6 / 71.9 / 0.013
89 / 73.4 / 0.0142
91.8 / 60 / 0.0038
87.4 / 72.5 / 0.0138
89.3 / 73 / 0.0138
90.6 / 74.5 / 0.0146
85 / 70.2 / 0.0126
Boston
Chicago
Denver
Detroit
New York
Philadelphia
Toronto
12.4
2.2
6.9
6.7
17.3
16.9
3.0
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