Manual J Flashcards
1
Q
What is the summer infiltration air quantity of an 1800ft² residential structure with 8ft ceilings of average construction in Greensboro, North Carolina?
A
48cfm Volume x Air Changes Per Hour(ACH) = CFH CFH ÷ 60 = CFM 1800 x 8 = 14,400ft³ 14,400ft³ x .2(ACH) = 2880CFH 2880CFH ÷ 60 = 48CFM Pg. 389 Manual J
2
Q
A block wall in a residential building has a stucco outside finish, metal studs with R-11 insulation, hollow cells, medium color and an interior finish. If 500ft² of this wall faces west in Raleigh, NC, what is the heat gain from this wall in the summer at design load conditions?
A
692btuh Cooling HTM = U-value x Table 4B CLTD Value Design temp = 92⁰ Daily range = M Group number = H Default indoor = 75⁰ HTM = .109 x 12.7 HTM = 1.3843 BTUH = 1.3843 x Area BTUH = 1.3843 x 500ft² BTUH = 692 Pg. 273, 345, 349, 383 Manual J
3
Q
What is the winter infiltration rate in cfm for a 4000ft², two story single family home of average construction that has one fireplace, 5 bedrooms and contains 36,000 cubic feet of air?
A
242cfm CFM = Air Changes an Hour x Volume ÷ 60 CFM = .37 x 36,000ft³ ÷ 60 CFM = 13,320 ÷ 60 CFM = 222 Add 20 cfm for the fireplace CFM = 222 + 20 CFM= 242 Pg. 389, 42 Manual J
