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Ventilation Calculation Method for Different Energy Codes
Ventilation Calculation Method for Different Energy Codes

The article explains how the ventilation rates (CFM (IP) or L/s (SI)) are calculated for different energy codes in cove.tool Updated over a week ago

# // ASHRAE 62.1 Ventilation Calculation Method

The outdoor airflow required (Vbz) is based on people-related sources and area-related sources. The equation for the calculation of Vbz is as follows:

Vbz = Rp * Pz + Ra * Az

Where:

Rp (Unit: CFM/person or L/s/person) = Outdoor airflow rate required per person as determined from Table 6.2.2.1

Pz = Number of people in the ventilation zone during use. cove.tool calculates this number based on the occupant density and the floor area of the project.

Ra (Unit: CFM/ft2 or L/s/m2) = Outdoor airflow rate required per unit area as determined from Table 6.2.2.1

Az (Unit: ft2 or m2) = Net occupiable floor area of the ventilation zone.

The outdoor airflow rate Vbz has the unit of CFM when IP system is selected and L/s when the SI system is selected.

# // California Title 24 Ventilation Calculation Method

The outdoor airflow rate to the zone (Vz) is determined according to the following equations:

Vz = Ra * Az (Equation 120.1-F)

Where:

Ra (Unit: CFM/ft2 or L/s/m2) = Outdoor airflow rate required per unit area as determined from Table 120.1-A.

Az (Unit: ft2 or m2) = Net occupiable floor area of the ventilation zone.

Vz = Rp * Pz (Equation 120.1-G)

Where:

Rp = 15 CFM of outdoor airflow per person

Pz = Expected number of occupants.

The maximum value from equations 120.1-F and 120.1-G is considered for outdoor airflow rate (Vz). Typically, the equation 120.1-F yields highest value so cove.tool refer that equation for the calculation of outdoor airflow rates.

It can be easily edited according to the project from 'Building System' tab.

# //United Kingdom National Calculation Methodology (NCM) Ventilation Calculation Method

The NCM Activity Database contains the l/s/p value for different building types. Cove.tool refers those values along with occupant density and the total floor area to calculate total L/s value for the project.

# //Australia National Construction Code (NCC) 2019 Ventilation Calculation Method

The minimum amount of introduced outdoor air for the system (Qf) shall be calculated as the greater of the area-based minimum and the occupancy-based minimum as follows:

(a) Area-based minimum:

Qf = (A * 0.35) L/s.m2

Where:

A (Unit: ft2 or m2) = Net occupiable floor area of the ventilation zone.

(b) Occupancy-based minimum:

Qf = (n * qf)

Where:

qf (Unit: CFM/person or L/s/person) = Outdoor airflow rate required per person as determined from AS 1668.2 standard.

n = Expected number of occupants.