Ventilation typically has more impact on your building's energy consumption than any other system. Although ventilation consumes relatively little direct energy, it in a large measure determines how much energy is needed to heat, cool, and humidify your building. Installing and modifying ventilation is regulated by codes. Further, there is evidence that inadequate ventilation is a major problem in commercial and institutional buildings. In a study of 450 buildings, 52 had poor indoor air quality due to inadequate ventilation. Common ventilation problems include: inadequate outdoor air supplied to the occupied space; poor air distribution and mixing, leading to stratification, draftiness, and pressure differences between office spaces; temperature and humidity extremes or fluctuations (sometimes caused by poor air distribution or faulty thermostats); and air filtration problems caused by poor maintenance of the building's ventilation system. If you want to pursue ECOs for your ventilation system, you should consider working with a professional consultant who is familiar with the local code and can identify existing ventilation rates, system operating practices, and appropriate energy saving operations. Energy and dollar savings can be substantial. The following are some typical no cost/low cost options.

Control Your Ventilation System When Your Building is Unoccupied

You may be able to limit the operation of your building's ventilation system during occupied hours only. In office building that is occupied on a 9-5 basis, 5 days/week, may be able to get by with just 40 hours of ventilation system use. Just 30 hours of use probably would be acceptable, assuming that the system can be shut off during the first and last hour of occupancy. Be sure to check local codes. You also need to make sure that the quality of the air in the building will be fully adequate to meet the needs of persons staying late or arriving early. Prepare a ventilation system operation schedule based on actual needs. Your building engineer should be responsible for insuring that the schedule is adhered to when manual control is involved. Savings may increase when automatic start/stop controls are used.

Control Ventilation During Occupied Hours

Some buildings are ventilated at a rate far in excess of values recommended by local building codes. By adjusting occupied period ventilation rates to the minimum specified rates specified by local codes, you could save energy and money. Most local codes are based on consensus standards developed by ASHRAE. ASHRAE Standard 62-1989: Ventilation for Acceptable Indoor Air Quality specifies minimum ventilation rates and acceptable indoor air quality. Table 2 of this standard specifies required rates of acceptable outdoor air. Standard 62-1989 stipulates a minimum of 15 cfm/person and specifies that, before adjusting the ventilation rates, you determine current ventilation rates, the typical occupancy patterns for the building, and the code requirements.

The following techniques may be used to reduce occupied period ventilation rates.

1. Lower ventilation rate by closing outdoor air dampers, until the desired volume of air is flowing. In such cases it is important to make sure dampers are in proper working order and correctly adjusted.

2. Cycle the ventilation system by turning it off for 15 to 20 minutes out of each hour. In this way, the building "coasts" on its existing air. This practice must be used with caution when air in some spaces may contain contaminants.

3. Discontinue ventilation to spaces that require none. Warehouses seldom need ventilation. Be aware of your building's occupancy patterns. In some operations, for example, ventilation rates are based on a peak occupancy that occurs only 10 to 20 of the time.

4. Close outdoor air dampers during the first and last hour of occupancy when the air must be heated or cooled, except when operating on economizer cycle.

5. Set a ventilation operation schedule so exhaust systems operate only needed.

6. Reduce exhaust air quantities as practical.

Reduce Operating Hours of Exhaust Systems

Local exhaust hoods are commonly used in food service and other areas in buildings. These hoods exhaust substantial quantities of air to maintain satisfactory capture velocities. Air that is exhausted must be made up by outside air, which usually must be conditioned. Unnecessary use of an exhaust hood wastes energy and money. You can install a timer to control these systems.