Carbon dioxide based ventilation control system demonstration.

Commercial buildings require mechanical ventilating systems, the specifications for which are included in the building codes. These codes specify the amount of outdoor air to be supplied per person for designed occupancy conditions. Many buildings such as retail establishments operate much of the time at occupancy loads well below the design. Thus, they are generally over ventilated and waste energy when operated according to the codes. A control system based on measurement of the carbon dioxide generated by the occupants was tested in a small bank in Pasco, Washington. Energy consumption, indoor air contaminant levels and occupant response were measured. Average energy savings of 7.8 percent over the code-specified ventilating rate were found to be possible for the Washington/Oregon area. Buildings similar to the one tested but located in six different cities in the Pacific Northwest showed savings that range from 2492 kWh in Astoria, Oregon, to 6563 kWh in Spokane, Washington. A payback of 2 to 3 years for a CO2 control system appears possible for the colder climates east of the Cascade Mountains. Nitrogen dioxide, formaldehyde, carbon monoxide and particulate levels were well below recommended limits. Measurement of subjective response showed that the occupants could not detect a difference between the background level of 300 ppm of CO2 and a level of 1000 ppm. An electric heating system was used that had marginal steady-state capacity. It was found that the supply air fan speed should be reduced when heating the building to avoid uncomfortable drafts.