Text Size:   A+ A- A   •   Text Only
Find     
Site Image

Demand-Controlled Ventilation Bldg Owner
What is a demand-controlled ventilation system?

A demand-controlled ventilation (DCV) system controls the amount of outside air brought into the building. It should provide the amount of outside air the human occupants need, and no more. This accomplishes two things. First, it saves energy by not heating or cooling unnecessary quantities of outside air. Second, it can provide assurance that sufficient outside air is being supplied to the occupants. Fixed ventilation systems provide constant, sufficient fresh air, but do so at the cost of heating or cooling excess air. Scheduled ventilation can provide fresh air at the correct rates at the right time, but run the risk of under or over-ventilation if schedule changes are not made at the appropriate times.
 
How much money will a DCV system save me?

The savings will vary greatly depending upon the building. However, energy savings are calculated to be as high as 60 percent for spaces that are lightly used but designed for large numbers of people (for example, gymnasiums). Also, buildings in predominantly heating climates such as the Pacific Northwest will get most of their savings during the heating season.
 
How does a DCV system work?

The system will use one or more sensors or systems to determine how many people are in a space. The ventilation system, typically part of the heating and cooling system, will adjust a damper to let more or less outside air into the building depending on what the sensor detects. For theaters, ticket sales or turnstile counters will provide the occupancy number. For gymnasiums, CO2 sensors will detect the presence of people.
 
What do I have to do?

First, it is important to work with the architect and designer to make sure they know how you will use the building. This will help them design appropriate systems. Future use of the building should also be considered. Some larger systems will contain most of the ventilation equipment due to building code requirements. There would be some additional sensors and controls to provide the demand-control features. It is important to commission the system to assure that the sensors are properly integrated.
 
Once installed, the system will run automatically. Annual building maintenance should include a check of system performance. The designer or builder should provide a procedure for the building owner on proper maintenance procedures.
 
What will the tenants think of the DCV system?

The tenants should not notice anything unusual. Proper ventilation should prevent the spaces from becoming stuffy, which should reduce complaints. It has been reported that the presence of a monitor actually improves tenant confidence in the quality of the air. Respond to serious tenant concerns by consulting with an air quality specialist and mechanical systems engineer.
 
How does the DCV system manage new building odors?

In new construction, there may be additional sources of odors. New furniture, carpeting, paint, office equipment, or other commercial processes may add contaminants that overwhelm the designed ventilation or occupants' perceptions. Sensors will not likely detect these unusual odors unless they are specifically designed to do so.
 
In these cases, the ventilation should be increased until the situation is resolved. Discuss with the designer and builder the options for modifying initial ventilation requirements.
 
Has anyone used a DCV system before?

Yes. Adoption of this technology was promoted as early as the 1970s. However, sensor technology made significant improvements in the 1990s. Infrared and CO2 sensors are now being used in creative, successful applications (see Case Studies). Schools are using CO2 sensors to monitor classroom air quality conditions, large department stores are using CO2 sensors to save energy, and large office buildings are retrofitting their ventilation systems to take advantage of both energy conservation and fresh air benefits.
DCV Guide: