where the quantities

where the quantities G3  and G2  are the moisture content of the outside and inside air respectively.  Referring to a copy of a psychrometric chart or to Figure 3, locate point 2 representing the inside design conditions of 80F db and 50% relative humidity. From point 2, project a horizontal line to the right to the moister content scale and read and read G2 = .011 lb moisture per lb dry air.  Similarly locate point 3 for the outside conditions of 95 F db and 75F dew point.  From the chart obtain G3  = .019 lb moisture per lb dry air.  Then the latent heat from the infiltration is
                              q = 4840 (20) (.019 - .011) = 774 Btu/hr
Appliances such gas ovens, ranges, and dishwashers add to the latent heat load in a building.  These contributions are estimated from the data of Reference 2 as follows:
Dishwasher           q = 420 Btu/hr Gas oven               q = 1200 Btu/hr
© Gary D. Beckfeld  Page 10 of 21
Gas range              q = 5600 Btu/hr