New Approach Results in High Building Efficiency Case Study

Offices

Iowa Project Showcases Geothermal Source, Dedicated Outdoor Air, Radiant Heating and Cooling

“As a non-profit organization, it is especially important for us to conserve budget dollars. We are pleased with the comfort this At a Glance system provides, and believe we are saving considerable energy • New 38,400 sq. ft . office expense in this new building through the design of the system.” building and training facility Speaking is Maddie Cafferty, Director of Support Services for located in Iowa City, Iowa Systems Unlimited, an Iowa City, Iowa organization that Systems • Owner concerned with energy provides supported living services, job training and employment to costs and indoor air quality adults with disabilities. The building is a 38,400 sq. ft. facility that • Solution: Combine strengths of houses administrative offices, training rooms and work areas for the three leading technologies: organization. ground-source heat pumps, dedicated outdoor air system, and radiant heating and cooling panels • System includes 8,000 cfm, 30- ton Venmar CES integrated ground-source heat pump energy-recovery ventilator with AHRI Certified™ performance from a total-energy wheel air-to- air heat exchanger; three five- ton ground source heat pumps supplying ceiling-mounted radiant heating and cooling panels. Systems Unlimited benefits from use of energy-efficient technologies

Limitations of VAV Systems This has been the first time he has used all of these tools in a single building. He Building HVAC designers have long indicates that to the best of his understood both the benefits and knowledge, this is the first example of all shortcomings of central-plant heating and three technologies being combined in an cooling using forced air. Development of entire building. The overall HVAC system the VAV approach in the last half of the operation was significantly enhanced by 20th century allowed improved efficiency extra insulation and joint sealing used by through better zone control and variable Shaw to create a very efficient building rates of ventilation, but some of the envelope. limitations of forced air combined heating and cooling remain. Air is an inefficient An Emerging Idea energy transport medium, and a significant portion of a building’s energy Amoroso credits a 2003 magazine article expense goes to the fan motors needed with stimulating his interest in using a for air distribution. Large-volume system of this type. The article, by Stanley Dedicated outdoor air ventilator uses recirculation of building air, as in the A. Mumma, Ph.D., discussed the an ARI certified total-energy wheel to recover energy between the typical VAV system, can lead to advantages of combining DOAS with exhaust and outdoor airstreams. distribution of contaminants throughout radiant ceilings and total energy recovery. the building. Mumma is an ASHRAE Fellow and Professor Emeritus of Architectural Taking a New Approach Engineering at Penn State University.

The building in Iowa City showcases an The article explained the potential of this alternative approach – one that promises type of system to solve problems with to dramatically improve building HVAC poor air distribution, poor humidity control plant efficiency while maintaining high and excessive energy usage for air comfort levels and offering improved handling. He points out that this hybrid indoor air quality. The system used in the system also has benefits of a very low Ground-coupled heat pump comes building has three primary elements. First, acoustic signature and excellent resistance factory packaged inside ventilator the building features earth-coupled heat to indoor air contamination being spread minimizing start-up time. pumps with an underground loop system through the building by recirculated as a heat source/sink. Second, both indoor air. sensible heating and cooling are principally achieved with ceiling radiant panels Combination of Concepts supplied by a highly zoned four-pipe water system. Third, building ventilation and According to Amoroso, his firm also has tight control of humidity levels are extensive experience with earth-coupled achieved with a dedicated outside air heat pump systems. It seemed logical to system (DOAS)—an integrated package combine such a system with overhead that provides building exhaust, total radiant panels and a DOAS design for the energy recovery from exhaust air, and Systems Unlimited facility. “The result,” Ceiling mounted radiant panels outdoor air ventilation. says Amoroso, “is truly a first-of-its-kind provide sensible heating and cooling building.” But he adds, “This is not to the occupants. Conditioned outdoor air is delivered directly to The Systems Unlimited building was untested technology. All of these elements the space to remove latent loads. designed by architect John F. Shaw of have been used successfully for years. Iowa City, and the HVAC plant was What makes this unique is the conceived by Vic Amoroso of A&J combination of elements.” Associates of North Liberty Iowa. Amoroso indicates he has been studying these types Amoroso explains that the use of of advanced approaches for years, and his overhead radiant heating-cooling panels firm has wide experience with all of the has been in widespread use in Europe for elements in the Systems Unlimited facility. quite a few years. In North America, some designers have resisted the idea because entire building on a design heating day. Amoroso, “We were attracted to this of concerns about condensation on cool The operating hours for the three units are solution because we had experience with panels from building humidity. “But in an balanced by the building control system. the Venmar CES product, and we like the installation like this, we use the DOAS fact that the entire unit is factory- system to tightly control building humidity, Loop System Uses Earth Energy assembled.” keeping levels below the dew point at all times.” He explains that by using a four- The underground loop system that feeds Outdoor Air Treated Before Use pipe arrangement, the same panel can the heat pumps was installed by A-One heat or cool. Normally in the cooling Geothermal of Earlham, Iowa, a regional Under normal operating conditions, a high mode, the circulating water temperature is earth-coupled heat pump loop specialist. proportion of the building supply air is around 60° F, so it is well above the dew The loop is a deep horizontal system that from outdoors. The building controls have point, further limiting the condensation was installed using directional drilling CO2 sensors to provide an input to control potential. techniques. The circulating fluid in the the amount of building air that is loop is a glycol-water, treated with recirculated after treatment. Heat recovery Overhead Panels Unobtrusive and chemical stabilizers. The glycol used was a from return air is accomplished in the Conserve Space food grade biodegradable product that Venmar CES unit using an enthalpy wheel even in the event of a with AHRI Certified™ performance, which The overhead panels are unobtrusive and leak will do operates between the supply and take up little vertical space above the no exhaust air flows. The wheel is 63 ceiling level. According to Amoroso, this inches in diameter and 10 inches shallow profile, along with the deep. It handles the entire system much smaller distribution ducts airflow of 8,000 cfm. needed for the DOAS system, means overhead building space The unit is designed to supply dry, can be reduced. This allows for filtered air to the facility at building- higher ceilings and the use of neutral temperatures. Energy to heat indirect lighting in certain areas. or cool incoming outdoor air and to The indirect lighting improves the dehumidify the air stream during the overall lighting efficiency and high-humidity months is provided by an reduces energy use. Because both harm integrated dual-compressor water source the volume and velocity of the to the heat pump, also connected to the ventilation air is much lower than with a water. The geothermal loop system. Hot gas reheat VAV system, the ambient noise level is mechanical from the compressors contributes to the reduced. There is no detectible noise from contractor for the entire dehumidification cycle. the ventilation air coming out of the project was Hometown Ventilation Energy Savings Using Energy diffusers. This is ideal for a work Plumbing and Heating of Davenport, Iowa. Recovery Ventilation environment. The key to the building air system is the Outdoor The operating heart of the system is in the Venmar CES packaged heat recovery and At Design Air basement of the building. Here is the ventilation unit. Venmar CES Inc. has been Conditions Temperature Savings termination for the underground loop manufacturing energy recovery equipment Summer Cooling 83°F DB piping for the heat pump system, where since 1952 in manufacturing facilities Energy 24 tons 76°F WB the multiple circuits connect to three 5-ton located in Canada at Saskatoon, Savings water-to-water heat pumps for cooling Saskatchewan and St-Léonard-d'Aston, and two 15-ton heat pumps for heating. Quebec. The indoor unit installed for this Heat Energy -11°F DB These supply hot and cold water for the project is 19 feet in length, and is Saved 671 MBh in Winter -11°F DB radiant panels. According to Amoroso, the designed with dual airflow tunnels – one system is designed so that two of the for outdoor air intake, treatment and three cooling units can carry the entire supply to the building ventilation system, building load on a design cooling day, and and the second for return air energy one of the two heating units can carry the recovery and exhaust. According to Constant-Volume Ventilation After a year of operation, the system has System Well-Accepted by proven to be an effective and efficient Occupants The treated supply air is distributed solution. Amoroso says, “We’ve been throughout the building using low velocity through extremes of heat, cold and Maddie Cafferty from Systems Unlimited, constant volume supply air fans, humidity, and the system has done a great notes, “People just don’t mention distribution ducts and overhead diffusers. job of maintaining comfortable indoor anything about comfort levels anywhere in Exhaust air is moved using variable speed conditions.” He notes that he was the building. To me, that means they are fans. Amoroso explains that the Venmar especially pleased how well the system comfortable.” Cafferty adds, “Overall the CES unit manages the latent aspect of handled periods of exceptionally high system has operated well. It’s been great.” heating and cooling operations, allowing humidity in July. Plans are currently underway to install the overhead radiant panels to handle the metering equipment on the HVAC plant to sensible element only. Using this approach, document actual energy usage. Cafferty a much smaller volume of air needs to be “We know energy says, “We know energy usage levels are moved, dramatically reducing the fan low, because Mid-America came in to energy cost for the building. usage levels are low, check their service meter because we were using so little energy.” According to Amoroso, when the building because the utility was in the design phase, he explained the Amoroso feels that the combination of benefits of this proposed system to the company came in to concepts used in the HVAC plant at Executive Director, Bill Gorman and to the Systems Unlimited has wide application in Board of Directors. He also showed them check their meter other buildings. “The things we did here an alternative plan using a conventional can be much more broadly used. With the chiller and VAV distribution arrangement. because we were rising costs of energy and the need for “I explained that the more conventional high indoor air quality, this is a great system would have a somewhat lower first using so little energy.” approach. I think we’ll be seeing more of it cost, but would have higher operating in the future.” costs and certain comfort disadvantages. After considering the options, they chose the most efficient option.” According to Amoroso, the “green” aspect of the project was important to the agency. “They take pride in the exceptional efficiency of the system.”

Utility Supportive of Concept

Amoroso points out that the local electric utility, Mid-America Energy, was supportive of the energy-efficiency elements of the building design. The utility provided an Unit schematic of factory packaged 8,000 cfm Venmar CES WSHP energy-recovery energy-efficiency rebate to offset some of ventilator showing the total-energy wheel, heating and cooling heat exchangers, supply and exhaust fans and integrated ground-source heat pump the costs of the project.

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