> For the complete documentation index, see [llms.txt](https://docs.betterbuilding.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.betterbuilding.io/user-guide/workflows/energy-efficiency/advanced-hvac/demand-controlled-ventilation.md).
# Demand-controlled ventilation
Demand-controlled ventilation is a ventilation control strategy that maintains indoor air quality by continuously adjusting the ventilation rate provided to a Space in response to changes in occupancy, usually measured by indoor carbon dioxide levels. The observable effects of modelling demand-controlled ventilation, compared to a fixed ventilation rate, would include;
* Decreased outside air flow rate at decreased occupancy rates (see HVAC Nodes report on Design Day simulation)
* Decreased space cooling energy
* Decreased space heating energy
Advanced HVAC enables demand-controlled ventilation on Air Handling unit systems to be considered.
{% hint style="success" %}
Model demand-controlled ventilation by selecting ‘Air Terminal’ settings and nominate ‘Yes’ for Control of Outdoor Air. Next, select the corresponding Air Handling Unit under the 'Outside Air System' settings, and then set Demand-Controlled Ventilation to 'Yes'. Hit 'Update, then 'Save'.
{% endhint %}
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