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2021 Washington State Residential Code <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 /> Equation 15-1 <br /> Ventilation rate in cubic feet per minute=(0.01 x total square foot area of house)+[7.5 x(number of bedrooms+1)] but not less than 30 cfm <br /> for each dwelling unit <br /> Table M1505.4.3(1) <br /> Whole-House Mechanical Ventilation Airflow Rate <br /> Number of Bedrooms <br /> Dwelling Unit 0-1 2 1 3 1 4 5 or more <br /> Floor Area(square feet) 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 <br /> l <br /> 2,001 -2,500 40 50 55 65 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 /> Table M1505.4.3(2) <br /> System Coefficient(Csystem) <br /> System Type Distributed Not Distributed <br /> Balanced 1.0 1.25 <br /> Not balanced 1.25 1.5 <br /> M1505.4.3.1 Ventilation Quality Adjustment <br /> The minimum whole-house ventilation rate from Section 1505.4.3 shall be adjusted by the system coefficient in Table M1505.4.3(2)based <br /> on the system type not meeting the definition of a balanced whole-house ventilation system and/or not meeting the definition of a <br /> distributed whole-house ventilation system. <br /> Qv=Qr*Csystem (Equation 15-2) <br /> Where: <br /> Qv = Quality-adjusted ventilation airflow rate in cubic feet per minute(cfm). <br />