Manufacturers Best Practice Guide
Central HVAC System: Basics
Heating, ventilation and air conditioning (HVAC) systems account for 40% to 60% of the energy used in U.S. commercial and residential buildings. Facility HVAC systems account for about 9% of industrial electricity use and about 7% of natural gas use.
HVAC systems regulate 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, and then venting the conditioned air to locations throughout the building as needed.
Industrial Chiller
Sometimes the easiest way to increase HVAC capacity is to focus on everything but HVAC equipment. Many factors contribute to temperatures within a building, including the building envelope, lighting and process equipment. Improving the energy efficiency of such non-HVAC equipment often reduces heating or cooling loads, meaning that the HVAC system does not need to run as hard or as long to maintain the correct temperature. For example, replacing an old T12 fluorescent lighting system with a T5 system reduces heating loads significantly while simultaneously cutting energy use and improving visual acuity.
Consider your entire energy action plan, and analyze the affect each measure has on HVAC operation. Schedule energy efficiency measures that have a significant impact first, then reassess whether or not adding HVAC capacity is warranted. Should installation of new equipment still be necessary, you will be able to right-size equipment, generally saving on the cost of equipment purchase and installation, as well as future costs related to running the new HVAC equipment.
An effective HVAC upgrade strategy depends 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 often are not 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% on their energy consumption by adjusting control set points and modifying existing equipment. Fine-tuning HVAC equipment also dramatically lowers CO2 emissions, an important consideration for companies participating in GHG emission reduction programs.
Integrating Systems:
"Energy-efficient, climate responsive construction requires a whole-building perspective that integrates architectural and engineering concerns early in the design process. For example, the evaluation of a building envelope design must consider its effect on cooling loads and daylighting. An energy-efficient building envelope, coupled with a state-of-the-art lighting system and efficient, properly-sized HVAC equipment will cost less to purchase and operate than a building whose systems are selected in isolation from each other."(Carl Ian Graham, PE)