Ventilation Control

Input Description for Ventilation Control : Demand Control Ventilation, Always On, and Off During Unoccupied Hours

Akshay Padwal avatar
Written by Akshay Padwal
Updated over a week ago

In most commercial occupied buildings, ventilation is provided to deal with two types of indoor pollution:

(1) odors from people

(2) off-gassing from building components and furniture

In addition to these, higher ventilation is also linked to higher cognitive abilities and productivity and showcase in this Harvard study.

Many types of medium to high-occupancy spaces, such as classrooms, multipurpose rooms, theaters, conference rooms, or lobbies have ventilation designed for a high peak occupancy that rarely occurs. As a result, ventilation can be reduced during the hours of operation when spaces are vacant or at lower than peak occupancy. When ventilation is reduced, building owners and operators save energy because it is not necessary to heat or cool as much outside air.

With analysis.tool, three types of ventilation control strategies can be simulated for the projects:

1 Demand Control Ventilation

Demand Control Ventilation (DCV) enables the automatic reduction of outdoor air intake below design rates when the actual occupancy of spaces served by the system is less than design occupancy. The system is controlled by sensors measuring the number of people or indoor air parameters or adapted criteria (e.g. CO2, mixed gas, or VOC sensors). Demand Control Ventilation is an effective strategy that can save a significant amount of energy in all climate zones.

When this option is selected, the ventilation is adjusted based upon the occupancy schedule located on the 'Usage and Schedules' page.

Important to note that the DCV won't be effective with constant air volume (CAV) systems as the CAV systems require constant outdoor air supply which doesn't vary based on the building occupancy.

2 Always On

As suggested by the name, the ventilation will always be on with this option. The fan energy would be higher with this option as it is not adjusted based on the building occupants.

3 Off During Unoccupied Hours

With this option, the ventilation system will be 100% operational during the active occupancy hours of the building and it will be switched off when it is unoccupied. The ventilation rate would be a constant designed rate since it doesn't vary based on the occupants.

The impact of the control type on the airflow is calculated according to the BS EN 15242 - Ventilation for Buildings - Calculation Methods for the Determination of Air Flow Rates in Buildings Including Infiltration.

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