The U.S. EPA’s ENERGY STAR Building Upgrade Manual recommends a stepwise approach to recommissioning, in which a series of strategically-ordered building “tune up” strategies are pursued in order. First, lighting and supplemental loads should be assessed, then the building envelope, then controls, then testing, adjusting and balancing, then heat exchange equipment, and finally heating and cooling systems. Most of these steps relate to HVAC system components or factors that will directly affect HVAC system energy consumption . For more information, the U.S. EPA’s ENERGY STAR Building Upgrade Manual should be consulted . Energy monitoring and control systems. An energy monitoring and control system supports the efficient operation of HVAC systems by monitoring, controlling, and tracking system energy consumption. Such systems continuously manage and optimize HVAC system energy consumption while also providing building engineers and energy managers with a valuable diagnostic tool for tracking energy consumption and identifying potential HVAC system problems. Several industrial case studies from the United States indicate that the average payback period for HVAC control systems is about 1.3 years .Non-production hours set-back temperatures. Setting back building temperatures during periods of non-use, such as weekends or non-production times, nft channel can lead to significant savings in HVAC energy consumption. Duct leakage repair.
Duct leakage can waste significant amounts of energy in HVAC systems. Measures for reducing duct leakage include installing duct insulation and performing regular duct inspection and maintenance, including ongoing leak detection and repair. According to studies by Lawrence Berkeley National Laboratory, repairing duct leaks in industrial and commercial spaces could reduce HVAC energy consumption by up to 30% . One commercial building in Apple Valley, California, adopted a technique called the mobile aerosol-sealant injection system to reduce duct leakage. The application of MASIS resulted in a reduction in overall duct leakage from 582 cfm to 74 cfm, leading to a 34% increase in the overall efficiency of the building’s HVAC system . Variable-air-volume systems. Variable-air-volume systems adjust the rate of air flow into a room or space based on the current air flow requirements of that room or space. Variableair-volume systems therefore work to more closely match HVAC load to heating and cooling demands, which reduces energy use. Adjustable-speed drives . Adjustable speed drives can be installed on variable volume air handlers, as well as recirculation fans, to match the flow and pressure requirements of air handling systems precisely. Energy consumed by fans can be lowered considerably since they are not constantly running at full speed. Adjustable-speed drives can also be used on chiller pumps and water systems pumps to minimize power consumption based on system demand.
Heat recovery systems. Heat recovery systems reduce the energy required to heat or cool facility intake air by harnessing the thermal energy of the facility’s exhaust air. Common heat recovery systems include heat recovery wheels, heat pipes, and run-around loops. The efficiency of heat pipes is in the 45% to 65% range , while the efficiency of run-around loops can be slightly higher, in the 55% to 65% range . Fan modification. Changing the size or shape of the sheaves of a fan can help to optimize fan efficiency and airflow, thereby reducing energy consumption. In a case study from the automotive industry, a Toyota plant optimized the sheaves of its fans in lieu of installing ASDs on fans. Toyota found better savings and payback periods with sheave modification than they anticipated to experience from ASDs . Efficient exhaust fans. Exhaust fans are standard components in any HVAC system. Mixed flow impeller exhaust fans offer an efficient alternative to traditional centrifugal exhaust fans. Mixed flow impeller fans are typically 25% more efficient than centrifugal fans, and can also be cheaper to install and maintain. The expected payback period for this measure is around two years . Use of ventilation fans. Ventilation fans installed in the ceilings of work areas can help destratify the workspace air, leading to better circulation of cool air in summer and warm air in winter, and more even distributions of temperature from floor to ceiling. Such fans can help to reduce the load on building heating systems by helping to “push down” warm air that rises to the ceiling during facility heating months.
Yasama Corporation U.S.A., a manufacturer of soy sauce, installed new high bay ceiling fans to improve air circulation at its Salem, Oregon, facility in 2004. Previously, to provide heat during the winter, the company operated ceiling-mounted heaters with 15 hp fans in its production area. However, the fans didn’t de-stratify the air in the production area’s tall ceilings, nor take advantage of the heat given off by process equipment. Furthermore, to provide ventilation in the summer, the company ran the heater fans in “fan only” mode in conjunction with six 3 hp exhaust fans to remove hot air. The new high-bay ceiling fans were operated using only 1.5 hp motors, which were expected to lead to electrical energy savings of 48,000 kWh per year and electricity cost savings of $2,500 . Furthermore, the company expected to save significant amounts of natural gas in heating months through reduced operation of the heaters. Cooling water recovery. If available, secondary cooling water from municipal sources can be leveraged to reduce chiller energy consumption. In Washington, Boeing partnered with Puget Sound Power and Light and the King County Department of Metropolitan Services to recycle secondary treated cooling water into its chiller system. By doing so, Boeing reduced its water consumption by 48 million gallons per year, leading to projected savings of 20% in its cooling energy consumption . As an additional benefit, Boeing also expected to save on refrigerants and treatment chemicals for its cooling tower water. Solar air heating. Solar air heating systems, such as Solarwall® , use conventional steel siding painted black to absorb solar radiation for insulation. Fresh air enters the bottom of the panels where it is heated as it passes over the warm absorber. Fans distribute the air. Using this technology, Ford Motor Company’s Chicago Stamping plant turned the south wall of its plant into a huge solar collector . Energy savings were estimated to be over $300,000 per year compared to conventional gas air systems. Capital costs were $863,000 resulting in a payback period of less than three years. In addition to energy savings, the system was said to provide clean fresh air for employees, even out hot and cold spots in the plant, and reduce emissions. However, this measure is only of interest for buildings in cold climates, and the potential benefits should be analyzed based on the local conditions of each site. Building reflection. Use of a reflective coating on the roof of buildings in sunny, hot climates can save on air conditioning costs inside. Two medical offices in Northern California used reflective roofs on their buildings; one reduced air conditioning demand by 8%, hydroponic nft the other reduced air conditioning demand by 12% . For colder climates, heat lost due to cool roofs also needs to be taken into account, and often negates savings. In addition to location and weather, other primary factors influence energy savings, such as roof insulation, air conditioning efficiency, and building age. Reflective roof materials are available in different forms and colors. Roof gardens on a flat roof improve the insulation of buildings against both hot and cold by providing both heat and air conditioning . In winter, green roofs can freeze, so they carry a slight heating penalty but often still yield net energy savings . In addition, a roof garden can increase the lifetime of the roof, provide and reduce runoff, and reduce air pollution and dust. Today, Germany installs over 10 million ft2 of green roofs a year, helped in part by economic incentives . The Gap Headquarters in San Bruno installed green roofs in 1997 . In addition to saving energy and lasting longer than traditional roofs, a roof garden absorbs rain, slowing run-off to local storm drains. Other simple options for decreasing building HVAC energy use exist for certain conditions. Shade trees reduce cooling for hot climates. Shade trees should be deciduous trees and planted on the west and southwest sides of the building . Trees planted on the north side of the building in cold climates can reduce heating in winter by shielding the building from the wind. Vines can provide both shade and wind shielding. Building insulation.
Adding insulation to a facility will nearly always result in the reduction of utility bills. Older buildings are likely to use more energy than newer ones, leading to very high heating and air conditioning bills. Even for a new building, adding insulation may save enough through reduced utility bills to pay for itself within a few years . Various states have regulations and guidelines for building insulation, for example, California’s Energy Efficiency Standards for Residential and Nonresidential Buildings . Going beyond regulated insulation levels may be economically beneficial and should be considered as part of the design of a new building, as well as for reconstruction of existing buildings. For refrigerated warehouses, much higher levels of insulation are preferred. Low emittance windows. Low emittance windows are another effective strategy for improving building insulation. Low emittance windows can lower the heat transmitted into a building and therefore increase its insulating ability. There are two types of Low-E glass, high solar transmitting and low solar transmitting . The U.S. DOE supports the development of new window and glazing technology, while ENERGY STAR provides a selection of rated Low-E windows. New window and glazing technology is being developed continuously around the world.22Turning off lights in unoccupied areas. An easy and effective measure is to encourage personnel to turn off lights in unoccupied building spaces. An energy management program that aims to improve the awareness of personnel with regard to energy use can help staff get in the habit of switching off lights and other equipment when not in use. Lighting controls. Lights can be shut off during non-working hours by automatic controls, such as occupancy sensors that turn off lights when a space becomes unoccupied. Occupancy sensors can save up to 10% to 20% of facility lighting energy use . Numerous case studies throughout the United States suggest that the average payback period for occupancy sensors is approximately 1 year . In a case study from the pharmaceutical industry, at the Merck office and storage building in Rahway, New Jersey, lighting panels were programmed to turn off automatically during expected periods of building non-use . Annual savings amounted to 1,310 MBtu per year, which corresponded to avoided energy-related carbon dioxide emissions of nearly 260 tons per year . Manual controls can be used in conjunction with automatic controls to save additional energy in smaller areas. Other lighting controls include daylight controls for indoor and outdoor lights, which adjust the intensity of electrical lighting based on the availability of daylight. An example of energy-efficient lighting control is illustrated by Figure 11.1, which depicts five rows of overhead lights in a workspace. During the brightest part of the day, ample daylight is provided by the window and thus only row C would need to be turned on. At times when daylight levels drop, all B rows would be turned on and row C would be turned off. Only at night or on very dark days would it be necessary to have both rows A and B turned on . These methods can also be used as a control strategy on a retrofit by adapting the luminaries already present. Exit signs. Energy costs can be reduced by switching from incandescent lamps to light emitting diodes or radium strips in exit sign lighting. An incandescent exit sign uses about 40 W, while LED signs may use only about 4W to 8 W, reducing electricity use by 80% to 90%. A 1998 Lighting Research Center survey found that about 80% of exit signs being sold use LEDs . The lifetime of an LED exit sign is about 10 years, compared to 1 year for incandescent signs, which can reduce exit sign maintenance costs considerably. In addition to exit signs, LEDs are increasingly being used for path marking and emergency way finding systems. Their long life and cool operation allows them to be embedded in plastic materials, which makes them well suited for such applications .