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gases by replacing polluted air with fresh air. Ventilation also assures that the arena will pass the required weekly air quality check that is required by the Minnesota Department of Health. If the rate of outside air introduced into an arena is not controlled properly the arena will be either under- or over-ventilated. If it is under-ventilated the arena will fail its air quality checks and possibly cause health problems for the occupants. Over ventilation increases energy consumption in two ways. First, during winter heated air is vented outside and make-up air taken from outside is brought into the building. The heating system works harder because the fresh air must be heated to the desired indoor temperature. Second, the introduction of warm moisture air during the summer into the cool arena causes moisture problems in the form of fog and condensation on the building which significantly increases the refrigeration system's energy consumption. The installation of sensors that measure COZ and CO along with an exhaust fan control system provide active and accurate control of the amount of fresh air brought into an arena. A minimum air flow will typically be called for during periods of limited use (i.e. ice skating lessons) or non- occupancy. The level of outdoor air is automatically increased during higher occupancy and reduced during low occupancy periods. The system is programmed to ventilate at its maximum capacity during the time the resurfacer is in operation and then to monitor for CO and adjust the ventilation rates as the concentration of CO decreases. Thus, ventilation levels are optimized for sufficient indoor air quality while energy costs are minimized. Installation costs vary depending on the number of exhaust fans and the type of control system that is currently in use. Typically these costs will be between $2,000 and $5,000 with a payback ranging from 1 to 5 years. This type of ventilation control has been implemented in several arenas around Minnesota. Arena Contact Person Phone Mankato Civic Center Marshal Madsen (507) 389-3000 *Time-of--Day Heating and Ventilation System Control Implementation of time-of--day controls for heating and ventilation systems can significantly reduce the operating expense of ice arenas. Manual operation of heating and ventilation systems is only efficient if ice arena employees adjust controls whenever heating or ventilation needs change. For example, when an internal combustion, engine-driven resurfacer is operating, employees must manually activate exhaust fans to provide adequate ventilation for the arena. If these fans are left on too long after resurfacing the arena will be over-ventilated which can cause moisture problems, added heating and cooling costs, and added refrigeration loads. The efficiency of manual controls is dependent on how well the arena staff understands the heating and ventilation systems and how often energy conserving practices are followed. Automatic operation of the heating and ventilation systems based on time-of--day and occupancy can result in optimum control of an arena's indoor conditions and minimal energy use. Some of the measures that can be installed to provide energy savings include: 1. Night setback of heating setpoints to allow arena temperature to drop at times of non-use. "Possible low-cost/no-cost improvement Energy Improvements in Minnesota Public Ice Arenas Project Page 11 Center for Energy & Environment