By now, the idea of getting things “on demand” is hardly new; it’s growing and affecting human behavior in a multitude of ways as we speak. It only makes sense that the same concept applied to building management—giving a building what it needs, when it needs it—would yield similar efficiencies as the on-demand economy, producing cost savings for facilities managers willing to embrace it.
Demand control ventilation—controlling the outside air supply based on real-time occupancy—is a simple way to increase your building’s operating efficiency and significantly reduce electricity costs at the same time. Just how much savings can you expect to see after implementing a demand control ventilation system? Keep reading to find out.
Demand Control Ventilation: How It Produces Savings
Building ventilation regulations exist to ensure adequate air quality for occupants. Carbon dioxide (CO2) may not be the most pernicious factor impacting indoor air quality, but it is often used as a surrogate for air quality and building occupancy level. The more occupants there are in a room or building, the more CO2 is released into the air. To prevent CO2 levels from rising too high—which can have a negative impact on occupants—outside air must be deliberately brought into the building through a ventilation system.
How much outside air does a building need? The American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) recommends 15 to 20 cubic feet per minute (CFM) of outdoor air per person. To adhere to this standard, most buildings are designed to ventilate at a fixed minimum rate per person based on the building’s occupancy rate.
The problem with this approach is that buildings aren’t usually fully occupied. And some spaces are vacant while others are not. As a result, the ventilation systems often bring in more outside air than necessary, which then has to be conditioned (heated or cooled) before being introduced into the environment. That means your air handling units—the motors and fans—are working harder than they need to in an effort to bring the outside air temperature down (especially if it’s warm and humid) or up.
Below is a chart depicting the ventilation in two different areas of a building. One is ventilated using traditional methods and is over-ventilated as a result; the other uses demand control ventilation to ensure high-quality air without overworking the system.
ASHRAE calculates that 20 CFM of outdoor air per person corresponds to CO2 levels of over 900 parts per million (PPM). The outside air being brought into Room B keeps CO2 levels in the 400 range, which means the ventilation system is being overworked all day long. Room A’s ventilation system keeps CO2 levels well under 900 PPM without overworking the system.
Demand control ventilation solves the problem of energy waste by monitoring CO2 levels and providing ventilation on an as-needed basis.
Here’s how it works:
- Sensors placed in various areas of the building monitor CO2 levels in real time. That information is critical because:
- It serves as a proxy for determining actual occupancy. The higher the level, the more people are in the space.
- It helps manage outside air intake. For commercial buildings, the EPA recommends CO2 levels below 1,100 parts per million. (Another guideline provided by ASHRAE calculates that 20 CFM of outdoor air per person corresponds to CO2 levels of over 900 parts per million.)
- The system continuously reads the sensor data and, based on CO2 levels, automatically directs the air handling units to adjust the outside air intake.
- If CO2 levels are adequate, it reduces the outside air intake.
- If CO2 levels are approaching the limit, it brings in additional outside air.
Demand control ventilation reduces the work for your heating and cooling units and maintains consistent, healthy air quality at the same time.
What kind of savings will you see with a demand ventilation control system?
From a financial perspective, demand control ventilation is one of the most impactful energy conservation measures facilities managers can implement. (Demand response is another.) Some analysis has shown that, on average, this type of system has a payback of 2.5 years with an average of 38 percent energy reduction in buildings. You could see anywhere from 15 to 20 percent savings on your energy bill as a result.
Want to know how you can get started with demand control ventilation?
Iota can help. Our smart building solutions make it easy for you to implement this money-saving strategy in a cost-efficient way. CO2 sensors combined with our BrightAI management platform can help you start realizing energy savings immediately. To learn more about our demand control ventilation solution—or other ways we can help make your building more energy efficient—get in touch.