Consider using Computational Fluid Dynamics (CFD) modeling to determine proper opening sizes and ensure proper airflow. Some energy modeling programs also have CFD analysis capabilities.
For mixed-mode ventilation, zone the plan into areas—mechanically ventilated and naturally ventilated—and follow separate compliance calculations for each area.
For mixed-mode and naturally ventilated spaces, the mechanical engineer should calculate the outdoor airflow rate and communicate the area requirements for operable wall or roof openings to the architect.
The mechanical engineer begins preliminary ventilation rate calculations during project programming in order to set ventilation quality goals for particular spaces and occupancies. The area of a given multi‐zone system should be broken down by ventilation zones, and all zones within that system must meet the minimum breathing zone ventilation air requirements as per ASHRAE 62.1‐2004. For a typical office space, the mechanical design consists of multiple ventilation zones for which compliance would need to be shown on an individual basis.
Increasing a project’s ventilation rate brings long-term cost benefits. Good indoor air quality can lower operational costs by increasing occupants’ health and productivity as well as the value and marketability of the building.
An integrated design approach among the mechanical engineer, architects, owners and occupants will facilitate design decisions that impact the HVAC design. For example, space planning decisions will impact the architectural programming of the space as well as access to natural ventilation.
Separately evaluate each space to determine air requirements and what type of ventilation will be best. Metabolic rate of the space activities and the occupant
