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MagiCAD 2024 feature highlight: VAV calculation

28.06.2023

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Variable air volume (VAV) systems are increasingly common thanks to the high level of efficiency and precision that they offer in controlling the indoor climate. New functions in MagiCAD 2024 for AutoCAD and Revit allow you to calculate VAV systems and evaluate their performance in different usage situations.

Why VAV systems?

A key benefit of variable air volume (VAV) systems is the flexibility and precision they allow in adjusting the air flow in different areas of a building according to changing demand levels. This helps cut down on costs and energy use, producing savings to building owners despite a higher initial installation cost.

VAV calculation in MagiCAD

VAV calculation in MagiCAD operates using two concepts: Zones and Schedules. Zones are a selection of air terminals that will have the same air flow rate (ex. the air terminals of a meeting room). Schedules are saved usage situations where different zones can have different air flows (ex. high air flow for meeting room, but medium air flow for the rest of the office).

With the help of Zones and Schedules, you can easily test different usage situations in calculation and verify how the system will perform in them.

How do I perform VAV calculation?

First, install air devices and define them as VAV Device in the product installation dialog. You can then define three different flow rates for the device: Minimum Flow, Normal Flow and Boost Flow. These will be used as the flow rate options in calculations.

If the device is not adjustable, you can still define the different flow rates for it, but this requires that there is a pressure measurer and a damper installed in the system to control the air flow.

Next, open Calculation Control and select VAV Zones. The dialog allows you to set up zones for the air terminals. For each zone you can add a Code and a Description and then edit the zone to add devices to it. Devices can be selected to a zone individually, with a rubber-band selection or according to existing Revit zones.

When you have set up all of your zones, click the Schedules icon to define different usage situations where each zone will have one of the pre-defined flow rates, for example a full office that requires boost flow in many zones, or an empty office at night with minimum flow for all zones.

The created schedules are used in the calculation report to recalculate the network according to different situations. Simply change the used VAV Schedule and update the report. You can also click on a report row to change the VAV air flow of a single zone if needed. This allows you to evaluate how the system will perform in the selected usage situation and how the different flow rates will affect it.

Insight and accuracy

A single usage scenario with one air flow rate is not enough to account for advanced and flexible ventilation systems. By performing VAV system calculations according to different usage situations you can get insight into how the system will work in each situation and what design changes are needed to accommodate changing demand levels.