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Mechanical systems are a necessary evil in most buildings. We’d prefer to rely entirely on natural ventilation and passive solar heating and cooling, but that’s not usually feasible. But we can design buildings so that the architecture does most of the work, and use mechanical systems to take care of the reduced heating, cooling, and ventilation loads that remain. Done right, this approach allows us to invest in highly efficient equipment and without spending more, because the equipment is so much smaller than it would otherwise have been.





Reducing HVAC loads

Some types of mechanical equipment don’t provide heating or cooling directly, but they reduce the amount of heating or cooling that’s needed. Air-to-air heat recovery systems, for example, exchange heat between outgoing and incoming air streams, so less energy is needed to condition the fresh air coming in. And ice storage systems using chillers to make ice and night, so that ice can be used during the day to cool the building. That reduces the size of the cooling equipment needed to maintain comfort, and reduces peak loads on the utility grid.

Renewable Energy

Solar energy isn’t just for photovoltaics (PVs) that generate electricity; it can also be used to heat water, to heat incoming air, or to heat a space directly. Heating needs can also be met with biomass, in the form of cordwood, pellets, or other cellulosic materials. Cogeneration systems that simultaneously generate heat and electricity, make the most complete use of the energy available from combustion. Cogeneration systems are covered under Electrical.

High Efficiency Equipment

Once loads have been reduced as much as possible with smart design and targeted use of equipment, it’s desirable to handle the remaining loads as efficiently as possible. High-efficiency boilers, furnaces, air conditioners, chillers, heat pumps, and the like all contribute to that efficiency. New split-system air conditioners or heat pumps are especially promising for homes and small commercial buildings due to their flexibility and efficiency. In larger buildings, cooling towers are key to releasing unwanted heat; these can be more or less efficient in both the amounts of energy and water they require.

Distributing the Comfort

Mechanical systems don’t just generate heat or cooling, they also have to deliver it to the occupied spaces. Traditionally this is done by blowing air through large ducts, often combining recirculated indoor air with specified amounts of fresh air to provide good air quality. But it takes much less energy to move heat using water than using air, so radiant heating and cooling systems are becoming more common. And keeping ventilation separate from comfort systems usually results in better overall control, higher efficiency, and better air quality.

Mechanical systems are a necessary evil in most buildings. We’d prefer to rely entirely on natural ventilation and passive solar heating and cooling, but that’s not usually feasible. But we can design buildings so that the architecture does most of the work, and use mechanical systems to take care of the reduced heating, cooling, and ventilation loads that remain. Done right, this approach allows us to invest in highly efficient equipment and without spending more, because the equipment is so much smaller than it would otherwise have been.



  • Conditioning Energy Recovery Ventilator (CERV)
  • Conditioning Energy Recovery Ventilator (CERV)
  • Build Equinox
  • Conditioning Energy Recovery Ventilator (CERV)
    Build Equinox
    Build Equinox’s Conditioning Energy Recovery Ventilator (CERV) is an energy recovery ventilator that also monitors indoor air quality. Engineered for residential use, the CERV provides approximately 3,800 BTU/hr heating and 5,500 BTU/hr cooling capacities while monitoring inside and outside temperatures and relative humidity. The unit Fresh Air Control Module monitors interior carbon dioxide and VOC levels and, using preset indoor air quality set points (in parts per million), adjusts fresh air flow accordingly to maximize energy efficiency, air circulation in the home, and fresh air flow.
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  • Proctor Air Conditioning/Heat Pump Controls
  • Proctor Air Conditioning/Heat Pump Controls
  • Proctor Engineering Group, Ltd.
  • Proctor Air Conditioning/Heat Pump Controls
    Proctor Engineering Group, Ltd.
    Proctor Engineering Group manufactures products that improve the performance of air conditioners in dry climates, including the Western Cooling Control (WCC) system. Air conditioners are designed for humid climates, but in dry climates dehumidification is less important so the WCC allows the fan to run longer than standard AC controls to take advantage of cooling that is still present after the compressor turns off, saving up to 15% in energy, according to the company. The company also offers its Concept3 variable speed, electronically commutated motor and controls for furnaces and air handlers, which can reduce fan energy consumption by 50%. It can be climate optimized for greater dehumidification in humid climates and better cooling in dry climates, and it can accept humidistat input for improved efficiency in mixed climates.
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  • NovelAire ComfortDry 250 Dehumidifiers
  • NovelAire ComfortDry 250 Dehumidifiers
  • NovelAire Technologies
  • NovelAire ComfortDry 250 Dehumidifiers
    NovelAire Technologies
    NovelAire’s ComfortDry 250 dehumidifier uses a desiccant wheel and hot water to reduce indoor humidity, rather than a compressor and refrigerant. The desiccant wheel rotates and adsorbs moisture from the interior and then rotates in an outdoor airstream heated by hot water coils, drying the wheel and removing the moisture to the outdoors. The system does not require condensate drainage lines, and hot water can be supplied by a variety of sources, including water heaters or solar thermal systems. ComfortDry 250 can be ducted into an existing air handler or installed as a stand-alone system. Appropriate for spaces up to 3000 ft2, it can process 300 cfm, removing 105 pints/day (80°F, 60% RH) using hot water flowing at 1–2 gallons per minute at 120°F –160°F.
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  • AAONAIRE Energy Recovery Systems
  • AAONAIRE Energy Recovery Systems
  • AAON Heating and Cooling Products
  • AAONAIRE Energy Recovery Systems
    AAON Heating and Cooling Products
    AAON offers rotary Aaonaire air-to-air heat and energy recovery ventilators for commercial applications. These units are made from a polymer that has silica gel desiccant permanently imbedded, making them light, corrosion resistant, and easy to maintain, according to the company—and unlike aluminum wheels they do not require a drainpan.
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  • Ruskin Energy Recovery  Ventilators
  • Ruskin Energy Recovery Ventilators
  • Ruskin Company
  • Ruskin Energy Recovery Ventilators
    Ruskin Company
    Ruskin offers a variety of energy recovery ventilators (ERVs), including MiniVentilator and EnERVent units. The MiniVentilator (250–1000 cfm) is for indoor applications, whereas EnERVent and EnERVent+ (600–12,000 cfm) are for larger buildings and are available in indoor and outdoor units. EnERVent+ can be specified with options such as variable frequency blowers and CO2 sensors, and can be engineered to include a variety of heating and cooling options from gas heat to split systems.
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  • Greenheck Energy Recovery Ventilators
  • Greenheck Energy Recovery Ventilators
  • Greenheck Fan Corporation
  • Greenheck Energy Recovery Ventilators
    Greenheck Fan Corporation
    Greenheck offers a variety of energy return ventilators for commercial applications. Models include the MiniVent-450 and -750 for use where space is limited; ERV-10, -20, -45, -and 55 (500–6,000 cfm) that can be mounted indoors on the floor or ceiling for duct access; ERV-90 and -120 (5,000–12,000 cfm) for indoor and outdoor applications; and ERVe (1,000–6,000 cfm) for outdoor installation or roofs or pads. These systems are available with a variety of options, including CO2 sensors, frost control, network interface, and more. The company also offers models that provide supplemental heating and cooling.
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  • Panasonic ECO-i VRF Systems
  • Panasonic ECO-i VRF Systems
  • Panasonic Corporation of NA
  • Panasonic ECO-i VRF Systems
    Panasonic Corporation of NA
    Panasonic’s ECO-i VRF (variable refrigerant flow) systems provide ductless heating and cooling for residential, commercial, and industrial applications. The ECO-i is available in a variety of sizes, from providing 3 to over 26 tons heating/cooling depending on model and configuration. Larger units can be connected to as many as 40 indoor units, yet require a single refrigerant pipe network and only one building penetration. Redundancy is built into large, multiple-compressor configurations, so if one compressor fails the other will take over. Wireless and wired controllers are available to manage temperature, airflow, and systems diagnostics. The ECO-i uses non-ozone-depleting R-410a refrigerant.
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  • Pansonic Mini- and Multi-Split Systems
  • Pansonic Mini- and Multi-Split Systems
  • Panasonic Corporation of NA
  • Pansonic Mini- and Multi-Split Systems
    Panasonic Corporation of NA
    Panasonic’s ductless mini- and multi-split heating and air-conditioning units are made for residential and light commercial applications. The mini-split (or "single split") air conditioners come in wall, ceiling, or concealed-duct configurations, supplying 2.2–3.3 tons of cooling with a seasonal energy efficiency ratio (SEER) as high as 28.5 and HSPFs of 12.5. The company’s multi-split systems are available with cooling only or with a heat pump; both have inverter-controlled variable speed condensers that run between two and four air handlers. The cooling-only units supply up to 1.6 tons of cooling and the cooling/heating configurations supply up to approximately 2.5 tons of cooling/heating. All Panasonic split systems use non-ozone-depleting R-410a refrigerant.
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  • LG Split Systems
  • LG Split Systems
  • LG CNS America
  • LG Split Systems
    LG CNS America
    LG’s “Duct-Free Split” (DFS) systems supply air conditioning and heating for residential and light commercial applications. A variety of wall and ceiling mounted single-zone (mini-slit) systems are available, including the Art Cool system, which is capable of heating and cooling performance as high as 28 SEER and 12 HSPF, and is available in ¾- and 1-ton capacities. The Art Cool Gallery wall-mounted unit incorporates a frame where artwork can be displayed, allowing the units to blend in. The company’s other single-zone units have up to 3.5-ton capacities; a ceiling-concealed ducted system is also available. The company’s Multi F multi-split systems can support up to eight air indoor units and have capacities up to 4.5 tons. LG uses inverter-driven compressors and R-410a refrigerant.
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  • Bosch Greensource Ground- and Water-Source Heat Pumps
  • Bosch Greensource Ground- and Water-Source Heat Pumps
  • Bosch Thermotechnology
  • Bosch Greensource Ground- and Water-Source Heat Pumps
    Bosch Thermotechnology
    Bosch’s CDi Greensource ground- and water-source heat pumps have two-speed scroll compressors and variable-speed electronically commutated motors on fans to provide energy-efficient heating/cooling and humidity control. The units operate at up to 37 EER under partial load (28.0 EER under full load) with a COP up to 5.7 (5.1 under full load). A system that uses waste heat from the compressor for domestic hot water is also available as an option. The CDi Greensource uses R-410a refrigerant and comes with a 10-year warranty. Bosch also offers commercial ground- and water-source heat pumps through the company FHP.
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  • Westinghouse iQ Drive Heat Pumps
  • Westinghouse iQ Drive Heat Pumps
  • Westinghouse Electric Corporation
  • Westinghouse iQ Drive Heat Pumps
    Westinghouse Electric Corporation
    iQ Drive inverter-driven rotary compressor heat pumps are manufactured by Nordyne and sold by Westinghouse, as well as by Broan, Frigidaire, Maytag, Tappan, and Nu Tone. Common in split systems, Nordyne is the only manufacturer that offers this technology in packaged heat pumps. The iQ Drive inverter and compressor work in tandem to match refrigerant flow to heating and cooling loads, similar to fuel injection in a car, and adjust fan speed accordingly. These units can run at very low speeds continuously, eliminating the large energy demands from compressor start up while still providing dehumidification. Available in 2–5 ton capacities, iQ Drive heat pumps operate at up to 22 SEER cooling and 10 HSPF heating. They use R-410A refrigerant and come with a limited 10-year warranty.
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  • Nu Tone iQ Drive Heat Pumps
  • Nu Tone iQ Drive Heat Pumps
  • Broan-NuTone LLC
  • Nu Tone iQ Drive Heat Pumps
    Broan-NuTone LLC
    iQ Drive inverter-driven rotary compressor heat pumps are manufactured by Nordyne and sold by Nu Tone, as well as Frigidaire, Maytag, Tappan, and Westinghouse. Common in split systems, Nordyne is the only manufacturer that offers this technology in packaged heat pumps. The iQ Drive inverter and compressor work in tandem to match refrigerant flow to heating and cooling loads, similar to fuel injection in a car, and adjust fan speed accordingly. These units can run at very low speeds continuously, eliminating the large energy demands from compressor start up while still providing dehumidification. Available in 2–5 ton capacities, iQ Drive heat pumps operate at up to 22 SEER cooling and 10 HSPF heating. They use R-410A refrigerant and come with a limited 10-year warranty.
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  • Nordyne iQ Drive Heat Pumps
  • Nordyne iQ Drive Heat Pumps
  • Nordyne
  • Nordyne iQ Drive Heat Pumps
    Nordyne
    Nordyne manufactures energy-efficient iQ Drive inverter-driven rotary compressor heat pumps that are sold by Broan, Frigidaire, Maytag, Nutone, Tappan, and Westinghouse. Common in split systems, Nordyne is the only manufacturer that offers this technology in packaged heat pumps. The iQ Drive inverter and compressor work in tandem to match refrigerant flow to heating and cooling loads, similar to fuel injection in a car, and adjust fan speed accordingly. These units can run at very low speeds continuously, eliminating the large energy demands from compressor start up while still providing dehumidification. Available in 2–5 ton capacities, Nordyne’s iQ Drive heat pumps operate at up to 22 SEER cooling and 10 HSPF heating. They use R-410A refrigerant and come with a limited 10-year warranty.
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  • Maytag iQ Drive Heat Pumps
  • Maytag iQ Drive Heat Pumps
  • Maytag Appliances
  • Maytag iQ Drive Heat Pumps
    Maytag Appliances
    iQ Drive inverter-driven rotary compressor heat pumps are manufactured by Nordyne and sold by Maytag, as well as by Broan, Frigidaire, Tappan, Nu Tone, and Westinghouse. Common in split systems, Nordyne is the only manufacturer that offers this technology in packaged heat pumps. The iQ Drive inverter and compressor work in tandem to match refrigerant flow to heating and cooling loads, similar to fuel injection in a car, and adjust fan speed accordingly. These units can run at very low speeds continuously, eliminating the large energy demands from compressor start up while still providing dehumidification. Available in 2–5 ton capacities, iQ Drive heat pumps operate at up to 22 SEER cooling and 10 HSPF heating. They use R-410A refrigerant and come with a limited 10-year warranty.
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  • Frigidaire iQ Drive Heat Pumps
  • Frigidaire iQ Drive Heat Pumps
  • Frigidaire
  • Frigidaire iQ Drive Heat Pumps
    Frigidaire
    iQ Drive inverter-driven rotary compressor heat pumps are manufactured by Nordyne and sold by Frigidaire, as well as Broan, Maytag, Tappan, Nu Tone, and Westinghouse. Common in split systems, Nordyne is the only manufacturer that offers this technology in packaged heat pumps. The iQ Drive inverter and compressor work in tandem to match refrigerant flow to heating and cooling loads, similar to fuel injection in a car, and adjust fan speed accordingly. These units can run at very low speeds continuously, eliminating the large energy demands from compressor start up while still providing dehumidification. Available in 2–5 ton capacities, iQ Drive heat pumps operate at up to 22 SEER cooling and 10 HSPF heating. They use R-410A refrigerant and come with a limited 10-year warranty.
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