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ASHRAE+62.1-2022+(1) - Page 030

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Table 6-7 Minimum Openable Areas: Single Openings [ a]

Vbz/Az,

(L/s)/m [2]

Vbz/Az,

cfm/ft [2]

Total Openable Areas in Zone as a Percentage of Az

HS/WS0.1 0.1 < HS/WS1 HS/WS > 1

1.0 0.2 4.0 2.9 2.5

2.0 0.4 6.9 5.0 4.4

3.0 0.6 9.5 6.9 6.0

4.0 0.8 12.0 8.7 7.6

5.5 1.1 15.5 11.2 9.8

where Vbz = breathing zone outdoor airflow, per Table 6-1. Az = zone floor area, the net occupiable floor area of the ventilation zone. WS = aggregated width of all single outdoor openings located at the same elevation. HS = vertical dimension of the single opening or the least vertical dimension of the openings where there are multiple openings.

a. Volumetric airflow rates used to estimate required openable area are based on the following:

  • Dry-air density of 0.075 lbda/ft [3] (1.2 kgda/m [3] ) at a barometric pressure of 1 atm (101.3 kPa) and an air temperature of 70°F (21°C)

  • Temperature difference between indoors and outdoors of 1.8°F (1°C)

  • Gravity constant of 32.2 ft/s [2] (9.81 m/s [2] )

  • Window discharge coefficient of 0.6

Table 6-8 Minimum Openable Areas: Two Vertically Spaced Openings [ a]

Total Openable Areas in Zone as a Percentage of Az

Vbz / Az,

(L/s)/m [2]

Vbz / Az,

cfm/ft [2]

Hvs8.2 ft (2.5 m) 8.2 ft (2.5m) < Hvs16.4 ft (5 m) 16.4 ft (5 m) < Hvs

As/Al0.5 As/Al > 0.5 As/Al0.5 As/Al > 0.5 As/Al0.5 As/Al > 0.5

1.0 0.2 2.0 1.3 1.3 0.8 0.9 0.6

2.0 0.4 4.0 2.6 2.5 1.6 1.8 1.2

3.0 0.6 6.0 3.9 3.8 2.5 2.7 1.7

4.0 0.8 8.0 5.2 5.0 3.3 3.6 2.3

5.5 1.1 11.0 7.1 6.9 4.5 4.9 3.2

where Vbz = breathing zone outdoor airflow, per Table 6-1. Az = zone floor area, the net occupiable floor area of the ventilation zone. Hvs = vertical separation between the center of the top and bottom openings’ free operable area; in case of multiple horizontally spaced pairs of openings,

use shortest distance encountered. As = openable area of smallest opening (top or bottom); in case of multiple horizontally spaced pairs of top-and-bottom openings, use aggregated areas. Al = openable area of largest opening (top or bottom); in case of multiple horizontally spaced pairs of top-and-bottom openings, use aggregated areas.

a. Volumetric airflow rates used to estimate required operable area are based on the following:

      - Dry-air density of 0.075 lbda/ft [3] (1.2 kgda/m [3] ) at a barometric pressure of 1 atm (101.3 kPa) and an air temperature of 70°F (21°C)

      - Temperature difference between indoors and outdoors of 1.8°F (1°C)

      - Gravity constant of 32.2 ft/s [2] (9.81 m/s [2] )

      - Window discharge coefficient of 0.6

b. determine the effect of pressure losses along natural ventilation airflow paths on the resulting flow rates,

including inlet openings, air transfer grills, ventilation stacks, and outlet openings during representative conditions of expected natural ventilation system use.

c. quantify natural ventilation airflow rates of identified airflow paths accounting for wind induced and

thermally induced driving pressures during representative conditions of expected natural ventilation system use.

d. design to provide outdoor air in quantities sufficient to result in acceptable IAQ as established under Sec tion 6.2.1.1 or 6.3 during representative conditions of expected natural ventilation system use.

6.4.3 Control and Accessibility. The means to open required openings shall be readily accessible to building occupants whenever the space is occupied. Controls shall be designed to coordinate operation of the natural and mechanical ventilation systems.

28 ANSI/ASHRAE Standard 62.1-2022

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