HVAC System Heats, Saves at YMCA
The challenge was to find new ways to meet the HVAC needs for a new YMCA while keeping costs down. An HVAC system, with a custom-manufactured heat-recovery process, achieved both objectives.
By nature, collaborative efforts between two large organizations can be difficult to manage. When four organizations are involved, many see a recipe for disaster. Not so at the C.W. Avery Family YMCA in Plainfield, IL, which is a shining example of how a school board, hospital, city, and park district can successfully work together to create a 52,000-sq.-ft. facility to serve a community. One of the achievements of this effort is its HVAC system, which meets all expectations, saved on construction costs, and will save money in the long run.
Examples of HVAC savings for the facility range from innovative thinking in maintaining pool temperature and natatorium humidity levels, to nontraditional placement of heating/cooling units and the use of a fabric duct system.
|The C.W. Avery Family YMCA’s eight-lane pool features a heat-recovery system from Dectron that maintains the water temperature at 80 F, while also keeping relative humidity at 50% and room temperature at 82 F in the 9,100-sq.-ft. natatorium.|
Syed Ahmad, P.E., project engineer with R.L. Millies & Assoc., Munster, IN, and Stephen Doonan, vice president, DeKalb Mechanical, DeKalb, IL, used heat-recovery options and air-distribution designs that afforded smaller and more efficient blower motors; fabric, instead of labor-intensive metal ductwork; and many other innovative HVAC, value-engineering solutions that saved the $10.1-million facility tens of thousands of dollars in construction costs.
Additionally, annual operational savings will add up. For example, a custom-manufactured Dry-O-Tron DS-202 by Dectron Inc., Roswell, GA, uses a heat-recovery process to heat the eight-lane indoor pool’s water to 80 F, while simultaneously keeping the 9,100-sq.-ft. natatorium’s relative humidity and space temperature at a comfortable 50% and 82 F, respectively.
Ahmad estimated that the pool-water heating feature on the dehumidifier cuts energy usage by 20% to 25% when compared with a standard swimming-pool water heater with no heat recovery.
The Avery dehumidifier is also fitted with a factory-installed, natural-gas, back-up boiler by Raypak, Oxnard, CA. Specifying this feature saved thousands of dollars in piping, equipment-placement labor, and mechanical-room space.
The boiler’s rooftop location, along with the dehumidifier, is also safer because the combustion process is removed from interior mechanical rooms where flammable and corrosive pool chemicals are present. “We’ve learned early on that it’s a significant savings and just makes more sense to specify a boiler as part of the factory-engineered, rooftop package unit,” Ahmad said. He has designed several other natatoriums in the past.
The supply of domestic hot water for the entire recreation center is handled with boilers from Lochinvar Corp., Lebanon, TN.
Because Dectron is capable of custom manufacturing, another R.L. Millies energy-saving specification places 3,300-cfm (minimum code) and 16,100-cfm (purge) exhaust fans before the evaporator coil and relies solely on a supply-air fan to re-circulate natatorium air during unoccupied hours, at a significantly reduced energy rate. The exhaust fans operate only during occupied periods, as opposed to a conventional economizer that operates a full sized return fan in conjunction with the 24/7 supply fan.
R.L. Millies’ configuration specification, which was overseen and facilitated with Dectron by manufacturer’s representative, Imbert Corp., Niles, IL, is capable of introducing 100% outside air to purge the space effectively during super-chlorination periods. Splitting the two exhaust fans makes the dehumidifier more efficient with both net-sensible cooling and fan operation. In comparison with conventional economizer operation, the resultant annual energy savings from the 9,100-sq.-ft. natatorium’s dehumidifier is more than $40,000.
Further energy efficiency comes from Ahmad’s specification of Dectron’s Smart Saver heat recovery coil option. The Smart Saver extracts heat from the exhaust air stream to preheat the outdoor air, thus requiring less energy for make-up air heating.
R.L. Millies’ energy-efficient design began as pre-design meetings with the project architect, Clifford A. Bender, A.I.A., director of architecture, Healy, Bender & Assoc., Naperville, IL, and general contractor, Nicholas & Associates, Mt. Prospect, IL. The synergy between the HVAC design and the architecture assured the building orientation of windows on the South, West, and East sides to promote more solar gain in the winter and less in the summer months. Consequently, the building orientation resulted in a smaller-sized dehumidifier, compared with other similar-sized natatoriums. Smaller blowers will also produce significant long-term energy savings over the life of the building.
Aesthetically, Bender’s ample use of floor-to-ceiling windows and Ahmad’s request for an open-architecture ceiling, instead of a drop ceiling, subliminally give swimmers the more open feeling of outdoor swimming.
Collaboration between the architect and engineer is also evident in the rooftop dehumidifier positioning, which is in close proximity to the 6-ft.-high outside wall of the natatorium. Instead of a large amount of costly fabrication and installation labor associated with installing rooftop equipment, the rooftop ductwork merely projects 5 ft. laterally out of the unit and through the natatorium wall to the interior perimeter duct connection. Additionally, this short ductwork run, with no elbows, reduced static pressure and allowed use of smaller horsepower motor/blowers that saved approximately 5% of the system air-distribution operational costs.
DeKalb Mechanical’s Doonan’s value-engineering contribution was replacing the round, spiral, aluminum-duct specification with fabric ductwork, thus saving $35,000 in ductwork labor and materials. Additional savings will come from the fact that the 30-in.-dia. fabric doesn’t need protective epoxy paint coatings, which is a direct construction cost, and the long-term maintenance savings. Additionally, the Avery YMCA stands to gain long-term indoor-air-quality benefits and other reduced maintenance costs because fabric ducts do not attract condensation, which can proliferate biological contaminants. If a duct needs cleaning, it’s designed to be disassembled and commercially laundered.
Ahmad’s even-air distribution on the windows is dependent on linear diffusers that run the length of the perimeter fabric duct system. Air stratification within the interior portions of the space, such as over the pool water, is eliminated with six strategically placed return vents that meet at a manifold near the dehumidifier.
Another long-term, operating-cost reduction came from Doonan, who suggested using package rooftop units by AAON, Tulsa, OK, that efficiently use heat recovery enthalpy wheels to reclaim exhausted locker room heat. Throughout the rest of the building, Doonan switched out the specified five large rooftop units in place of 20 smaller units, manufactured by Carrier, Syracuse, NY, and AAON rooftop package heating/cooling units, for a total savings of $110,000. Since most of the smaller units are positioned over the rooms they serve, much of the savings came from the reduced ductwork materials and labor of larger, centrally located units. “I think they will see operational savings from this switch too, because instead of running one large unit that services many rooms, they can get isolated room temperature control from a single unit,” Doonan said.
While controlling costs helped make the project successful and more functional, the HVAC design also created a comfortable swimming environment that will eventually pay off in attendance figures. “We toured other natatoriums in the area and most of them were pretty muggy,” said Pamela Lee, executive director, C.W. Avery YMCA. “We notice a definite difference in our new pool facility because it seems so much more comfortable.”