“High-performance buildings” is kind of a buzzword in the HVAC industry nowadays. Technological advancements in both BMS software and HVACR equipment allow building owners and facility managers to moderate energy usage like never before. And considering HVACR equipment is one of the largest drivers of energy consumption in commercial buildings, more and more owners are commissioning and retrofitting existing buildings to create better performing structures. The following case studies showcase several ways commercial buildings have been designed and retrofitted to high-performance standards.
RONALD MCDONALD HOUSE
Ronald McDonald House (RMH) Charities’ New York City location is the largest facility of its type in the world. The 13-story brick building was built in 1989, and though living space within the 70,000-square-foot structure is modern, the systems that served it were original until recently.
“The boiler and chillers were past their life cycle,” said Ike Beyer, owner of Integrated HVAC Systems and Services Inc., the 30-person mechanical company that partnered with Rochester, New York-based MEP engineering firm Energy Concepts, for the design/build retrofit.
“As a nonprofit organization, the project’s payback and sustainability were equally important as the initial cost,” he said.
Both Energy Concepts and Integrated were early adopters of combined heat and power (CHP), or cogeneration technology. Decades of experience would ultimately lead to a solution that surpassed facility managers’ expectations for comfort and sustainability.
“From the inception of this this project, the goal was to better serve children and families battling cancer,” said Mel Farrell, chief engineer at RMH New York.
Long before plans for a retrofit were drawn up, Energy Concepts began a feasibility study to determine if a CHP plant would be right for the facility. After two years of research and data collection, it was determined that on-site cogeneration equipment would provide the heating, cooling, and domestic hot water (DHW) loads while supplying 95 percent of the building’s power needs.
Integrated HVAC Systems and Services installed a natural gas-fired IntelliGen CHP unit on the roof of the 13-story building. The prepackaged unit combines a 250kW generator to produce power for the building. Heat from the engine — up to 1.5 million Btu under full load — is rejected into a large plate-and-frame heat exchanger.
Three loads draw from the heat exchanger: DHW production, the building’s two-pipe fan coil units when in heating mode, and three 50-ton Yazaki absorption chillers on the 12th floor.
“Because the absorption chillers are now the only source of cooled water, both the heating and cooling elements in the building are entirely dependent on a source of hot water,” explained Beyer. “During maintenance of the CHP unit, or in the unlikely event of failure, we needed complete redundancy in the form of condensing boilers. This is the case with almost every cogen application.”
A pair of Laars NeoTherm condensing boilers provides double redundancy. The larger, at 1.7 MBtu, more than matches the output of the CHP unit. The second 1 MBtu boiler is in place for further peace of mind. If the CHP unit is turned off for any reason, the boilers fire together, each modulating to roughly 50 percent to meet design load.
“The role of the boilers in this situation is critical, even more so than in a conventional heating application,” said Don Rathe, president of Rathe Associates, the manufacturer’s representative firm that helped to specify components for the hydronic system. “In addition to carrying the heating and snowmelt loads, the cooling system would also go down if the boilers failed to run.”
“Farrell wanted the very best equipment money could buy; efficiency and dependability were his key concern,” explained Chris Cafer, associate and senior mechanical engineer at Energy Concepts. “Ike and I had to figure out how to make it all fit.”
Given their small footprint, high efficiency, and Beyer’s familiarity with the NeoTherm line, the boiler selection process was brief.
“We’ve used Laars boilers for years now, even in conjunction with other CHP projects,” said Beyer. “I’ve yet to encounter an issue that hasn’t been resolved with a short phone call to the Rathe Associates.”
Integrated also replaced the building’s existing domestic hot water equipment with two 85-gallon instantaneous, indirect-fired water heaters. A new BAS simplifies the otherwise complex systems, and a snowmelt zone outside now keeps guests safe and eliminates costly winter sidewalk maintenance.
This renovation means that for many years to come, the NYC facility is going to continue serving families in some of their darkest hours.
The 17-story office structure at 615 Chestnut Street, Philadelphia, was constructed in 1981, five years after America celebrated its bicentennial. Yet the building’s declaration of energy and utility independence didn’t happen until 33 years later, when its owners agreed to sweeping improvements at their facility.
The 380,000-square-foot building is one of the city’s main offices for the FBI, Secret Service, Social Security, and Internal Revenue Service (IRS). The office/multi-use building also houses private firms and a restaurant.
The original heating and cooling system, a 1,000-ton water-source heat pump system being served by four 250-ton forced draft cooling towers and a bank of cast-iron gas-fired boilers, was aging and underperforming. The need for replacement was the perfect opportunity to look at the returns for investing in new technology. The old heating and cooling system had undergone many “patch” replacements, and most of the original water-sourced heat pumps were replaced through the years.
According to Casey Younkins, sales engineer with Kennett manufacturer’s rep firm Energy Transfer Solutions, building managers phased in gradual replacement of all original heat pumps.
“Through the years, the loads in the building increased, and the old towers and boilers were having difficulty meeting the peak demand,” said David Parmiter, engineer, Urban Engineers Inc. “The challenge was to not just replace the equipment but to improve performance while also reducing energy consumption. We performed a comprehensive evaluation that included a return on investment calculation.”
According to him, the original, closed-circuit cooling towers were consuming large amounts of water through evaporation. Also, even after several repairs to the coolers, the boilers were unable to maintain loop temperatures for cold morning startups. Parmiter led the effort to engineer retrofit solutions for the facility that included options for replacing the towers and boilers and optimizing controls.
“Ultimately, the purpose of this renovation was to make a dramatic impact in the entire system’s energy performance and water use,” added Younkins.
The owner’s directive to the system improvements was threefold: prioritize energy efficiency, minimize maintenance, and streamline water treatment. The owners had real appreciation for the fact that one firm, Evapco, could avail single-source manufacturing of the cooling towers, the control system, and water treatment.
Parmiter and Younkins specified two eco-ATWB-E cooling towers that would provide the most tower capacity while staying within the size and weight limitations of the existing support structure. The new coolers would reduce the total connected fan motor horsepower from 160 hp down to 60 hp — a 60 percent reduction in energy for the fans alone. To improve water and energy savings, the new coolers offer both evaporative and dry cooling simultaneously and three modes of operation: evaporative, dry, and water efficient (simultaneous wet/dry).
Control technology was developed to connect and manage all of the new system’s critical functions while also measuring and analyzing water inlet and outlet temperature with ambient dry bulb monitoring.
“The control easily interfaces with BACnet, so the owner was able to seamlessly integrate the Sage control into their building automation system,” said Younkins.
Following system installations in 2014, the building owners have experienced significant cost savings.
Engineers projected an average of 15,338 kWh per month over the old evaporative coolers — improvements that equate to a 75 percent savings in total energy use and cost after one year. Now, 40-some months after completing the retrofit at the facility, Parmiter learned from managers of the facility, who have tracked energy/utility performance rigorously, that the systems have saved almost $25,000/year in energy costs alone.
Tabco Towers is a large HUD apartment building in Towson, Maryland. When it came time to replace its aging packaged terminal air conditioning (PTAC) units, management looked beyond a simple in-kind replacement.
The building’s owner, Wishrock Investment Group, wanted to pursue Enterprise Green Communities (EGC) certification.
Melling Engineering and New Ecology, a nonprofit sustainability consulting firm, were both vital in the project’s early phases.
In addition to certification and efficiency, Wishrock was looking for a long-term solution that would provide greater comfort and control and reduced maintenance costs. Because wall penetrations for the PTAC units had caused maintenance issues in recent years, sealing up the building and controlling condensate drainage were goals as well.
Once a performance baseline for the 22-story, 180-unit building was established, attention turned to selecting a replacement HVAC system. There was initial skepticism concerning higher upfront cost, but what ultimately tipped the scales in favor of VRF was that the retrofit needed to take place while the building was occupied.
Fujitsu General’s Airstage heat recovery system was the No. 1 choice because of its overall efficiency. In addition, the Fujitsu refrigerant branch units fit in the small allotted spaces.
“We initially looked at both heat pump-only and heat recovery systems,” said Rick Melling, of Melling Engineering. “But the building’s tall, slender shape meant that most of the rooms have external walls. This creates the potential for widely varying loads and increases the likelihood of different zones simultaneously calling for heating and cooling. Being able to essentially ‘recycle’ heat, or extracting heat from one space and rejecting into another zone, was a big advantage.”
The final plan utilized 22 VRF condensers, most of which were 10 tons each. The units were paired together into 20-ton systems, with one system serving two floors. Single-bedroom apartments were outfitted with 18,000 Btu slim-duct units. Studio apartments are conditioned by wall-mount evaporators, ranging from 9,000 to 14,000 Btu. The PTAC units remained in service for the duration of the project. Without interrupting either the heating or cooling in any apartments, tenants were only displaced for several hours.
The entire project took roughly six months to complete.
“In simple numbers, modeling showed that the VRF retrofit at Tabco Towers would yield a 15-year payback before subsidy or grant money is accounted for,” said Marty Davey at New Ecology. “After receiving Enterprise Green Communities Certification funding, the real ROI should be five or six years.”
Centrally located in Tyler, Texas, the People’s Petroleum Building first opened its doors Nov. 5, 1932, as the tallest high-rise building in East Texas. Originally named People’s National Bank after its largest tenant, the 1930’s-era art deco office building is a prominent historical landmark that included several oil companies and related businesses that thrived during the East Texas oil boom.
After 70 years, the owners of the historic People’s Petroleum Building were ready to renovate and modernize the structure while maintaining the historical architecture and design.
To minimize disruption to the tenants, renovations were completed one floor at a time, beginning in 2012. The outdated chilled-water system, installed in 1969, was replaced with an efficient, reliable, and quiet Daikin Variable Refrigerant Volume (VRV) system. From the owner’s perspective, they were looking for a highly efficient system to reduce utility expenses, integrate with their existing BMS, save space, maintain the historical architecture, save on annual maintenance expenses, and spread the installation cost over several years.
All 15 floors of the mixed-use building, including a restaurant, retail store, and office space, were completed in 2017. Energy savings between 20 and 30 percent and annual maintenance savings of 50 percent is estimated with the Daikin VRV system when compared to the previous chilled water system. Unobtrusive, ceiling-mounted cassette units were installed flush with the ceiling throughout most of the building. Several ducted concealed and floor-standing concealed units were also fitted to hide above ceilings and behind walls as necessary to maintain the original historical interior architecture. A few wall-mounted units were also used for individual, unique spot cooling applications. A Daikin i-Touch Manager control system was installed to integrate the Daikin VRV heat pump system with the BMS, and individual Navigation Remote Controllers are used to control each zone.
UNIVERSITY OF ALABAMA
The University of Alabama (UAH) in Huntsville, Alabama, decided to build a new student center as a central location to support student affairs and activities of some 6,800 students. The university’s facilities staff sought an HVAC solution for the new 100,000-square-foot building that, in keeping with the school’s sustainability goals, would employ energy-efficient equipment.
Facilities staff considered two scenarios and their drawbacks. In the first, they could incorporate the new building load with the existing central plant. The staff would not be able to use their standard “chiller and boiler” design at the central plant because of space constraints in the cooling tower yard. In the second scenario, they could incorporate a chiller and boiler at the new student center, but the cost significantly exceeded the project budget. The final solution came when facilities staff at UAH, in consultation with Carrier Corp. and Mims Engineering, decided to install two Carrier AquaForce® 30XW heat recovery chillers in the central plant.
Rather than sending the heat the chillers produce to a cooling tower for dissipation, the condenser water (up to 138°F) is pumped into the existing hot water loop while also contributing chilled water to the cooling loop. This loop, which is also served by several Carrier AquaForce 19XR centrifugal chillers at the university’s central plant, cools a total of 767,121 square feet of space across several classroom, research, and residential buildings.
As part of their research, the facilities staff traveled to the Carrier factory in Charlotte, North Carolina, to view a heat reclaim chiller system at work.
“I call the 30XW units ‘heat machines’ rather than chillers because their sole purpose is to generate hot water for heating and reheat applications,” said Mark Cowherd, executive director of facilities for UAH. “The byproduct of this process is chilled water. We also use the chilled water for cooling. This system is super-efficient — we use every drop of hot and chilled water — and it has also saved a huge amount of potable water and natural gas. Show me a more sustainable design.”
In the first two years, the UAH system saved 6 million gallons of water, which translated into a savings of over $23,000. The system also saved the university $385,000 in energy costs.
In addition to these savings, the project has resulted in several accolades for both the university and the staff. The Charger Union student center is expected to attain LEED® Silver certification, and it received the 2013 Award of Merit from the North Alabama Chapter of Associated Builders and Contractors (ABC) Inc. Cowherd was also named the Association of Energy Engineers’ Energy Innovator of the Year 2015 for his region.
Publication date: 7/16/2018