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Central HVAC SystemControls and Load ReductionNothing affects comfort more than a building's climate control system. At the same time, nothing consumes more energy. Climate control accounts for roughly 41 percent of an office building's total electrical energy consumption - almost double that of any other building system. And, because daily high temperatures coincide with peak energy use, climate control equipment operates at its highest capacity during the most expensive utility rate time. Air conditioning alone is 45 percent of the total peak energy use of the commercial sector. In office buildings, climate control is most often provided through a central heating, ventilating, and air conditioning (HVAC) system. The HVAC system regulates temperature, humidity, and indoor air quality by drawing outdoor air into the air handling subsystem, conditioning this air in either the chiller (cooling) or heating subsystems to correct temperature and humidity, then venting the conditioned air to locations throughout the building as needed. Methods for upgrading HVAC systems depend on the particular characteristics of the building, the existing equipment in place, and any problems that might have been detected in indoor air quality. Central HVAC systems tend to be oversized and are not often set for optimal efficiency. Before adding additional cooling capacity, have a qualified engineer inspect the system to see if a redesign or tune-up may be in order. Companies have saved as much as 50 percent on their energy consumption by adjusting control set points and modifying existing equipment. Fine-tuning HVAC equipment also dramatically lowers CO2 emissions, important for companies participating in greenhouse gas emission reduction programs. To optimize HVAC performance and reap additional savings, install an enhanced automated control system along with compatible control equipment on building mechanical and electrical systems. The HVAC, lighting, fire and smoke detection, and security systems can all be integrated into an automated control system. Enhanced automation allows facility staff greater zone control by continuously monitoring and adjusting lighting and HVAC equipment based on occupant densities and environmental factors. This allows load curtailment during peak times when utility rates are highest. Enhanced automation also decreases occupant complaints arising from poor indoor air quality since zones rarely fall outside of control set points. Those problems that do arise are detected quickly and repaired fast, often before occupants have even noticed. Because equipment is optimized and operated in coordination with the full system, equipment life is extended and downtime for repair and maintenance is minimized. Other effective tools to reduce HVAC operating costs may only indirectly deal with the system. Before undertaking expensive retrofits, investigate ways to reduce heating and cooling loads. Lighting retrofits, building envelope improvements, and use of energy efficient office equipment all reduce heat buildup and lower cooling loads. Do these measures first, and make HVAC upgrades the last step in your energy program. This allows engineers to size the HVAC system, minimizing overall costs while ensuring that the entire building operates efficiently. Greenhouse Gas Emissions and Electricity
Resources Flex Your Power Product Guide: HVAC Systems and Programmable Thermostats U.S. Environmental Protection Agency, ENERGY STAR Building Manual: Heating and Cooling System Upgrades. Westphalen, D. and Koszalinski, S., Energy Consumption Characteristics of Commercial Building HVAC Systems, Volume One. Cambridge: Arthur D. Little, Inc., 2001. Developed for the Office of Building Technology State and Community Programs, U.S. Department of Energy. California Energy Commission, Enhanced Automation: Business Case Guidebook. May 2002. Institute for Research in Construction, Information on ventilation Cost-Effective Open-Plan Environment (COPE) Project: Ventilation Principles. DDC Online, Information on Direct Digital Controls (DDC) with an easy searchable guide to DDC manufacturers. |