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| Demand control ventilation helps controls cost! |
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Outside air is required by code on all new commercial construction. But outside air is also required on buildings, not by code, but by necessity. Even older existing buildings require outside/make up air. Why?
There are several reasons. The first that we may think of is restroom exhaust. Restroom exhaust is mandated by code on all commercial buildings. Many storage areas that contain chemicals, biologic or odor producing items must also have exhaust fans. Depending on the use of the building, additional outside air may be mandated. For example in skilled nursing facilities or hospitals, outside air is required to achieve the ACCA mandated 'air changes per hour'.
In other buildings outside air is needed to maintain the carbon dioxide at acceptable levels in occupied spaces. We exhale carbon dioxide. Fill up a building with people and you get a lot of carbon dioxide. Remember Apollo 13? They had problems with a build up of carbon dioxide. It could have proved fatal. They used a chemical scrubber to remove it. We use outside air to flush out this carbon dioxide and replace it with oxygen rich air. Additionally we dilute volatile organic compounds that are given off by carpets and other furnishings and other contaminates that we cannot see. Unfortunately, all this outside air costs money. It must be heated or cooled, dehumidified or humidified. It must be conditioned. What can we do to control cost?
"Demand control ventilation" is one way to lower the cost. Using a carbon dioxide or pressure sensor, these systems actively respond to outside air requirements, saving money by only introducing the amount of outside air needed. When the building is unoccupied, the outside air amount is reduced in some cases to zero! Using a fixed system which does not adjust, is like running your car's engine at full throttle while it's sitting in the drive way all night and it makes just as much sense! Beyond properly controlling the outside air intake, we must maintain and keep our outside/make up air properly adjusted. When a building is new, the system is adjusted to provide the specified air amounts. Many building owners feel that is the only time it needs to be done. That is a costly mistake.
Just as a car's engine needs to be maintained, (oil changes, tune ups, filters, etc) at regular intervals, an outside/make up air system must be maintained and tuned up periodically to function properly. The up front cost are more than offset by the continued savings month after month. Outside air is expensive! A properly adjusted and operating outside/make up air system saves money. In addition, the comfort of the occupants is enhanced and the building itself benefits. Temperatures, humidity levels, volatile organic compounds, carbon dioxide levels, particulates are all better controlled when the correct amount of air is introduced into the occupied spaces. Mechanical systems do not run as many hours, saving wear and tear on equipment, saving energy and keeping cost down.
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