ASHRAE+62.1-2022+(1) - Page 068
Extracted Content
And solving for window area,
A ------ w = Vbz
Az
Aw
[4] [] [5]
(K-6)
K3.3 Vertically Spaced Openings. The flow rate ( Vvs ) through vertically spaced openings of areas As (the smallest sum of opening areas, either upper openings or lower openings) and Al (the largest sum of opening areas, either upper openings or lower openings) is obtained using the following equation:
where
Aeff = effective window area, defined as
1 R [---]
Aeff
1
(K-7)
(K-8)
(K-9)
(K-10)
Aw = total sum of all opening areas
R = area ratio between As and Al
Aw = As + At
R
= --- A - s Al
H = shortest vertical distance between the center of the lowest openings and that of the upper openings.
All other constants are the same as in the single opening scenario. The required openable area as a fraction of the zone’s floor area is therefore calculated by equating the flow through two sets of vertically spaces openings ( Vvs ) to the goal flow rate ( Vbz ) obtained from Table 6-1.
Vvs = Vbz
Solving for window area:
Aw
R [---] Az
Az
(K-11)
(K-12)
K4. CONTROL AND ACCESSIBILITY (MIXED-MODE VENTILATION)
Mixed-mode ventilation is a hybrid system used to maintain IAQ and internal thermal temperatures yearround using both natural and mechanical ventilation systems.
a. Natural ventilation systems use natural forces such as wind and thermal buoyancy to ventilate and cool
spaces. b. Mechanical ventilation systems use mechanical systems with fans to supply and exhaust air from a
space, provide humidity control, and, if required, filter possible contaminants.
By preferentially using natural ventilation when outdoor air conditions are suitable, energy costs and carbon emissions can be minimized. Sensors are used to identify when natural ventilation is less effective at providing suitable indoor temperatures, humidity levels, and contaminant levels, and indicate that a transition to mechanical ventilation should occur. The transition between modes can be manual or automatic, as dictated by the needs of the owner/occupants. The use of each mode when appropriate will ensure yearround acceptable IAQ.
66 ANSI/ASHRAE Standard 62.1-2022