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fal l 2009 / retrof itmagazine.com

[ sys t e m r e t r o f i t s ]

When It Comes to hVAC, WhAt Do You WAnt to KnoW?

In the next several Issues, Retrofit magazine will highlight various HVAC technologies and strategies you can implement in your building or home to reduce your energy use and carbon footprint. The magazine also will demonstrate methods to improve indoor air quality and conserve potable water through HVAC equipment.

For example, you can expect to read articles about the following HVAC retrofit technologies:

Variable frequency drives Energy-recovery ventilators Building-automation systems Thermostats (programmable, intelligent and internet accessible) Economizers (air and waterside) Zoning (air and water) Heat pumps (air-cooled, water source and geothermal) Solar water heating Variable refrigerant flow Dedicated outdoor air systems Temperature-reset strategies High-efficiency boilers

Instantaneous water heaters Demand-controlled ventilation Cooling-tower water conservation Air purification to reduce mold, bacteria, viruses, VOCs, smoke and odors

What would you like to see this magazine cover when it comes to mechanical equipment? Please send us a note at editor@retrofitmagazine.com.

is comfortable for most do-it-yourselfers. Although there still are millions more light-ing upgrades that need to be identified and completed, we can almost assume you already know how to tackle this topic. But do you know how to reduce your HVAC energy consumption?

reduce loads • • • The first step is to reduce your loads. Do whatever you can to reduce the amount of heating and cooling required. This means better insulation and more of it. Get as much insulation as you can afford and install it correctly. Use ASHRAE’s “Advanc-ed Energy Design Guide” series for climate-specific recommendations. (Free downloads are available at www.ashrae.org/aedg.) Improving your building envelope will reduce your heating and cooling needs.

WHy RETRoFIT yoUR HEATInG, VEnTIlATInG AnD AIR-ConDITIonInG SySTEm? The answer is because it very well may be the largest energy user in your building. Really? many folks believe lighting is the largest energy user in buildings today. That is because most energy analysis and modeling is done by mechanical engineers, and we do a great job of presenting the energy-use data so it incorrectly shows that lighting energy usage is the problem and not our beloved mechanical systems. Sometimes we will show energy in terms of dollars instead of BTUs or kilowatts because gas is often much less expensive than elec-tricity in many areas. other times we simply show HVAC as separate categories—fans/pumps, heating, cooling and service-water heating, etc.—to make the lighting number stand out.

GettinG startedwith hVaC retrofitsefficient mechanical systems can contribute to building energy savings

However, when you add heating, cooling and ventilating together and treat them as a single system (as they generally are), you are looking at about 45 to 70 percent of the building’s energy use. That certainly exceeds the usual 10 to 30 percent lighting figures. of course a lot depends on climate, building type and building usage but, in general, HVAC should be a major target for those who are concerned about energy conservation.

StepS toward HVaC effiCienCyFantastic efforts have been made during the past decade or two to reduce lighting energy consumption. lighting ballast and bulb change-outs have been the low-hanging fruit of electrical- and energy-services companies for years. Changing bulbs also

WRITTEn By Ryan R. HogeR, LeeD aP

examine windows • • • If you don’t have windows with good thermal transmittance (U-Factor) and solar-heat-gain coefficient (SHGC), then you should retrofit them. Again, follow ASHRAE’s AEDG recom-mendations. U-Factor measures the heat transfer through a window, door or skylight and tells you how well the assem-bly insulates. The lower the U-Factor, the greater resistance to heat flow and the better the window’s insulation value. SHGC is the fraction of solar radiation admitted through a window, door or skylight. This tells you how well the assembly blocks heat caused by the sun. The lower SHGC, the less solar heat it transmits.

improve equipment • • • After you have improved your insulation and windows to reduce your heating and cooling needs, the next step is to invest in more efficient HVAC equipment. Different types of HVAC systems are rated using different methods by different authorities. Gas heating is typically rated in terms of percent efficiency, meaning how much energy comes in versus how much heat is output. Today, most gas-heating equipment is 80

percent efficient. older systems—those more than 20-years old—are often 65 percent efficient or less. High-efficient furnaces, boilers and heaters are often 88 to 95 percent efficient. Electric equipment is always rated by coefficient of perfor-mance, or CoP, with electric resistance heat being equal to 1.0. Air- or water-source heat pumps are typically 3.5 CoP (+/- 1.5 CoP depending on many factors, such as heat sink/source, compressor technol-ogy and outdoor temperature), which means they are three and half times more efficient than electric-resistance heat. Air conditioners are rated many different ways, often depending on the size and type of equipment. Residential A/C units are rated in seasonal energy efficiency ratio, or SEER. The legal minimum set by U.S. law and regulated by the U.S. Department of Energy is now 13 SEER. most older units—those more than 20-years old—are 6 to 10 SEER. The best residential units on the market today are 19 to 21 SEER. Commercial A/C equipment is rated in energy-efficiency ratio, or EER, and 9.5 to 13 EER is common. Unlike the residen-tial marketplace, EER is set by

building codes at the local level and enforced by the authority-having jurisdiction, so there will be different minimum EERs depending on location and sizes of equipment. For smaller equipment, 15.2 EER is the best on the market today. larger equipment, such as chillers, are rated in kW/ton Integrated Part load Value. Air-cooled machines are typically 1.2 kW/ton or lower, and water-cooled machines are often 0.72 or lower. These are average ratings. For air-cooled systems 1.04 is more efficient, and 0.33 is best for water-cooled systems.

enHanCe operationS Tight buildings are great, as is highly efficient equipment, but

how you operate your HVAC system is most important. There are dozens of examples of things that can be done to operate your existing system using less energy without sacrificing comfort. The basic premise is: Do not use more energy than you absolutely must. Implement setback sched-ules in your controls system to automatically change the heating and cooling settings when the building is not in use. Bring in only the code-required amount of outside air. Use waste exhaust air to pre-heat or -cool the ventilation air. much can be done very inexpensively to improve your equipment’s efficiency—sometimes with the equipment and controls you already own.