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WA Residential Code 2018 <br /> M1505.4.3 Mechanical Ventilation Rate <br /> The whole-house mechanical ventilation system shall provide outdoor air at a continuous rate as determined in accordance with Table •• <br /> M1505.4.3(1)or Equation 15-1. <br /> Ventilation rate in cubic feet per minute =(0.01 x total <br /> square foot area ofhouse)+ [7.5 x (number of bedrooms <br /> 1)] but not less than 30 cfm for each dwelling unit. <br /> Equation 15-1 <br /> TABLE M1505.4.3(1) <br /> WHOLE-HOUSE MECHANICAL VENTILATION AIRFLOW RATE <br /> NUMBER OF BEDROOMS \LD 5VY) _ Vn-GA-i <br /> DWELLING UNIT <br /> FLOOR AREA 0-1 2 3 4 .' 5 or more <br /> (square feet) <br /> Airflow in cfm <br /> <500 30 30 35 45 50 <br /> 501 -1,000 30 35 40 50 55 <br /> 1,001 —1,500 30 40 45 55 60 <br /> 1,501 -2,000 35 45 50 60 65 <br /> 2 <br /> 2,001 -2,500 40 50 55 6 5 i 70 <br /> 2,501 -3,000 45 55 60 70 75 <br /> 3,001 -3,500 50 60 65 75 80 <br /> 3,501 —4,000 55 65 70 80 85 <br /> 4,001 —4,500 60 70 75 85 90 <br /> 4,501 —5,000 65 75 80 90 95 <br /> For SI: 1 square foot=0.0929 m2, 1 cubic foot per minute=0.0004719 m3/s. <br /> TABLE M1505.4.3(2) <br /> SYSTEM COEFFICIENT Csystem) <br /> SYSTEM TYPE DISTRIBUTED NOT DISTRIBUTED <br /> Balanced 41.0) 1.25 <br /> Not balanced 1.25 1.5 <br /> TABLE M1505.4.3(3) <br /> INTERMITTENT OFF WHOLE-HOUSE MECHANICAL VENTILATION RATE FACTORSa.b <br /> RUN-TIME 0/0 IN EACH <br /> 4-HOUR SEGMENT 50% 66% 75% 100% <br /> Factory 2 / 1.5 1.3 1.0 <br />