Vintage factory converted to healthcare offices
Energy improvements key to success.
The Providence Center, a nonprofit, behavioral healthcare organization now occupies the 72,000 square-foot brick building that was once part of the Eagle Screw Company. After the building was renovated to provide offices and meeting rooms, Providence Center purchased it in 1996. But it wasn’t until 2013 that a mechanical system retrofit brought all facets of the 1875 building into the 21st Century. Operating costs fell while indoor air quality and comfort levels rose.
"These old brick buildings are solid and beautiful, but they sure don’t win any energy awards," said Bob Pritchard, director of facilities and projects at The Providence Center. "We couldn’t keep the facility at a comfortable temperature in the winter, and spent huge dollars attempting to."
"Also, there are two full levels of the building below grade," continued Pritchard. "The entire east side of the building has a 40-foot tall flagstone foundation, which inherently means moisture within the envelope. Air quality was a concern year-round. The building was just damp and musty."
Victory Mechanical was hired to design and install components to provide a solution. Don Fleck, PE, systems engineer at Victory, brought in rep firm Emerson Swan during the design.
"The work was split into two phases; a hydronic retrofit in late 2011, and a more invasive air-side upgrade in early 2013," said Tim Eaton, at Emerson Swan.
The first challenge was the basement mechanical room. Four existing 1 MBtu boilers consumed nearly 18,000 gallons of fuel oil each year. The Victory crew removed the oil boilers and installed four, HTP Mod Con 850 gas-fired boilers. The new condensing boilers offer 96% efficiency, a vast improvement over the roughly 65% efficiency the facility had before the retrofit.
The building’s existing fin-tube radiation was serviceable, as were a handful of fan-coil units in stairwells. "With four modulating boilers, each with a 5:1 turndown, this system literally has 20 stages of heat input," said Fleck. "It’s like having 20 tiny boilers, and each one only turns on if it’s needed. So you’re never using more fuel than the building really needs."
Taco pumps on the boilers and the building’s primary loop provide efficient, maintenance-free circulation. For further space and initial cost savings, Victory installed Taco Plus Two multi-purpose valves with each secondary pump. The compact valve is effectively five valves in one, combining all the functions that are normally required on the discharge side of a centrifugal pump in a single body; a shut-off valve, a non-slam check valve, a balancing valve and a flow metering valve. It’s easily field-converted from a straight pattern to a 90-degree pattern for easy use in nearly any application.
The Providence Center didn’t have to wait long to see savings from the boiler retrofit. Once connected to the natural gas utility line — fuel expenses were $66,000 below the prior winter, meaning the estimated 4.8-year ROI is tracking nicely.
Next, says Pritchard, the company tackled the problems with humidity and indoor air quality. "We knew we were using way too much electricity for air conditioning," he added, "and temperatures varied as much as 15°F from room to room." The building’s 37 independent HVAC systems couldn’t maintain desired conditions.
In 2013, work on the airside project started. Fleck and Eaton had designed a dedicated outdoor air system around a new product.
The solution to all ailments would come in the form of a packaged rooftop unit. The 20-ton Modine Atherion unit now installed at Providence Center is used for dedicated outdoor air supply. It features condensing gas heating technology and an optional ERV module with an energy recovery wheel, the effectiveness of which typically exceeds 60%.
Ductwork a Challenge
Gary Tsacoyianis was the controls and startup technician from Victory for the Atherion unit. "My job was easy," he says, "But I’m told the ductwork was another story." The most challenging part of the project came when Victory technicians installed 5,100 lineal feet of duct in the building. The old brick and large timbers slowed progress, but when finished, there was neutral-temperature, fresh air delivery to the farthest reaches of the facility.
With the Atherion’s ERV module, a portion of the cooling load has been lifted from the existing independent systems, allowing the system to easily meet demand. And with up to 94% efficiency, the unit is able to condition outdoor air in the winter without adding heating load for the modulating boilers downstairs.
The Atherion’s gas heating capability is provided by Modine’s Conservicore technology; a dual heat exchanger that provides condensing efficiency and up to 100°F temperature rise. Paired with the Energy Recovery Module, the unit provided everything needed at Providence Place.
Pressure Balance Problems
"Before the retrofit, we had major issues with negative pressure in the building," said Pritchard. "You had to heave on the door to get in the building. Once open, it’d literally suck you in."
Three vertical utility shafts in the building — plus the elevator shaft – acted as big chimneys, providing a perfect conduit for warm air to leave the building. This — and the building’s inoperable windows — created a vacuum.
As annoying as the pressure issue was, it also created a huge waste of energy as conditioned air was pulled out of the building, especially in the winter. During the retrofit, the shafts were used to run ductwork between the floors, and were then sealed off. But Victory took the pressure solution a step further. Aside from providing cost-effective make-up air, the Atherion is also tasked with maintaining positive pressure within the building.
A barometric pressure sensor in the building corresponds with the Atherion’s VFD-powered fan in order to maintain the .02" H2O setpoint — similar to that of a typical pharmaceutical clean room. "On average, the Atherion is exhausting 3,800 CFM and supplying 4,000," said Tsacoyianis.
"We’re absolutely, 100 percent satisfied with the retrofit," said Pritchard. "The energy savings are staggering and the indoor environment is now infinitely better." But the project also resulted in a few less-tangible benefits.
The new control system installed by Victory allows domestic water to be shut off within the building during unoccupied hours — another big benefit because the facility had suffered a few overnight leaks in the past.
This project in Providence is an excellent example of giving new and energy-efficient life to a very old building using 21st century boilers, airside systems, and control technologies. Many other buildings out there are candidates for such renovations.
Project benefits at glance:
- $66,000 annual fuel savings from heating retrofit alone
- 4.8 year ROI is on-track
- Vastly improved indoor air quality
- Negative pressure issues resolved
- Boiler repair and maintenance now virtually non-existent
- Consistent temperatures throughout building in both heating and cooling mode
- Programmable thermostats enable save energy during unoccupied hours
- Domestic hot water leaks are no longer a concern due to the new control system.
Modine Atherion Ventilation Unit
This article originally appeared in the Gas Technology Summer 2016 issue.