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Union Mill: Rebirth of Maryland’s Largest Stone Mill

Once the largest cotton duck (canvas) producer in the world, the historic 86,000-sq-ft Union Mill, located in Baltimore, MD, has been restored into a vibrant mixed-use complex of 56 one- and two-bedroom apartments (designed exclusively for school teachers new to Baltimore), 30,000 sq ft of office space (designed for Baltimore’s education, health and human-service nonprofit organizations) and a 1,500-sq-ft café restaurant in the former boiler-house building.

Seawall Development Co. used the Baltimore City Green Building Standards to bring back to life Union Mill’s long-productive campus of historic buildings, vacant for only three of the past 146 years. Seawall’s team consisted of architects, engineers and contractors who were all veteran managers with extensive LEED, energy-efficiency and sustainable-development experience. Their combined talents and vision for Union Mill paid off when the developer received a letter from the manager of Baltimore Gas & Electric’s “Smart Energy Savers Program,” stating that their proposed energy-efficiency improvements were to be rewarded with a cash rebate of $164,258.

Using real estate to create social change
Seawall’s development philosophy is to revitalize functionally inoperable buildings in historic neighborhoods into nonprofit office space and apartments for organizations that bolster Baltimore’s public school system. The company strives to provide affordable housing and office space for new teachers coming to Baltimore.

“The Baltimore School System recruits 700 to 1,000 new teachers each year,” said Evan Morville, Partner, Seawall. “Many come from the best universities in the country to work under the Teach for America program. These highly educated and motivated graduates don’t know where to live, and it’s difficult for them to find housing.

“We want to roll out the red carpet and provide them with affordable, smart housing close to the inner city,” said Morville. “Their days are tough, and we wanted them to be able to come home to a comfortable, teacher-friendly environment where they can share the challenges of their day with their peers. We knew they would also need space for collaborative, shared amenities like workout rooms with showers and teacher resource rooms for late-night lesson plans and copying—all under one roof. We also put the word out to 25 local educational nonprofits to have affordable space close to our teachers. A local merchant responded to our call by providing high-speed copiers in a 24/7 resource center.”

Certified under Baltimore City Green Building Standard
In August 2007, the Baltimore City Council mandated that the city establish Green Building Standards for commercial and multi-family residential buildings larger than 10,000 sq ft, either newly constructed or extensively modified. The code reads as follows: Projects electing to follow the LEED compliance pathway are exempt from this requirement, but must submit LEED Silver or higher documentation prior to expiration of the LEED Pathway Compliance Period.

“Consulting with my design team, we decided that a LEED Silver equivalency was the proper way to go for Union Mill’s sustainability program,” said Morville. “All three Seawall partners are Baltimore natives, so it was a thrill when we received word that Union Mill was the first project to be certified under the Baltimore City Green Building Standard.”

Estimated annual energy savings of 450,000 kWh
Needless to say, the partners were pleased by the utility rebate of $164,258. “A utility incentive of this size is extremely rare in our business,” said Mike Babcock, Co-founder and Managing Partner of Sustainable Building Partners LLC. “What it all boils down to is this: Through our comprehensive whole-building, hourly energy-simulation model, we were able to project for Baltimore Gas & Electric an overall savings of 450,000 kWh annually.”

Babcock explained that the baseline modeling methodology used for this analysis is consistent with LEED, ASHRAE 90.1 protocols and best practices. The overall performance was driven by the synergies between the R2-Series VRF zoning system from Mitsubishi Electric Cooling & Heating, high-performance make-up air, energy-recovery ventilation, premium-performance double-pane low-E windows and thermal mass.

“Every day my professional life revolves around measuring and analyzing whole-building energy performance, comparative system analysis and ROI,” said Babcock. “The thing that most impresses me about the Mitsubishi Electric VRF zoning technology is the combination of 100% INVERTER-driven compressors, quiet and premium-efficiency indoor units, free integrated energy recovery and, lastly, no need for supplemental electric resistance heating. Typical heat pumps on the market today begin to engage electric resistance auxiliary heat when the outdoor temperature drops below 25°F, while the Mitsubishi Electric VRF zoning system does not.”

VRF zoning system
When specifying Union Mill’s HVAC system, the design team had a number of variables to consider with the 146-year-old structure. They had to take into consideration sightlines for the placement of mechanical equipment on and around the historic structure and the city of Baltimore’s zoning and noise restrictions. They could not afford to disrupt the unique, historic nature of the mill, and with stone walls that were more than 2-ft thick, demolition would be prohibitively costly. This grand building had a pitched roof that would not support boilers, chillers or outdoor condenser units. A traditional split heat-pump system would call for up to 160 individual split-system units that would be impossible to hide. Placing 160 outdoor units in the courtyard or behind the building was not an option, so a conventional split system with heat pumps was out of the question. The team had few choices.

The mechanical engineers at Allen & Shariff Engineering LLC; HVAC independent sales representative The Joyce Agency; and distributor Aireco Supply Inc. suggested to Morville that he consider a VRF zoning system from Mitsubishi Electric.

The VRF zoning equipment costs were less than expected. Mitsubishi Electric’s outdoor units are known for their low noise, with a small footprint. Also, indoor units come in diversified configurations, which provided the architect with numerous choices for installation in a variety of zones.

The HVAC team liked the fact that the R2-Series simultaneously cools and heats different zones within the mill. Heat energy is collected from the zones in cooling mode and then transferred to the zones that require heating. The shared heat energy between the indoor units means less of a need for the outdoor unit, which translates to maximized energy-efficiency. The multi-zone design allows one outdoor unit to support up to 50 indoor units. Installation efficiency and equipment savings stem from the system’s requiring only two pipes from outdoor to branch circuit controller, and then two pipes from there to each indoor unit. Only one small penetration is required through the 26-in.-thick walls for the two bundled refrigerant lines to connect the outdoor unit to the BC controller.

The zoning system has TG-2000 software, which allows integrated tenant billing. Through sub-metering, Seawall can bill each tenant for their equivalent share of energy use. Finally, with Mitsubishi Electric’s Lossnay energy-recovery ventilators, Seawall can provide an outside-ventilation air system, with heat recovery, integrated into the VRF zoning system’s CMCN controls scheme.

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The Team
Seawall Development Co., Baltimore, MD
Marks, Thomas Architects, Baltimore, MD
Energy Engineer
Sustainable Building Partners LLC, Fairfax, VA
Mechanical Engineer
Allen & Shariff Engineering LLC, Columbia, MD
HVAC Contractor
Charles A. Klein & Son Inc., Baltimore, MD
HVAC Independent Sales Representative
The Joyce Agency, Springfield, VA
HVAC Distributor
Aireco Supply Inc., Savage, MD

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