New YMCA Saves Big With Custom Configuration
The Plainfield, Ill.-based 52,000-square-foot facility had the watchful eyes of a large donor, plus the high profile status as the first YMCA internationally to be a collaborative effort between a school board, a hospital, a city, and a park district. Therefore the innovative HVAC design helped provide more value for the $10.1 million recreation center, not to mention reducing future operating costs.
Syed Ahmad, P.E., project engineer with R.L. Millies & Assoc., Munster, Ind., and Stephen Doonan, vice president, DeKalb Mechanical, DeKalb, Ill., used heat recovery options, air distribution designs that afforded smaller and more efficient blower motors, fabric versus labor intensive metal ductwork, plus a number of other HVAC value engineering solutions that saved the facility tens of thousands in construction costs.
Ahmad estimated Dectron's unique pool water heating feature on the dehumidifier cuts energy usage by 20 to 25 percent versus using 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, Calif., a 1 million MBH boiler. Ahmad's specification of this feature saved thousands of dollars in piping, equipment placement labor, and mechanical room space. Because the boiler is located on the roof with the dehumidifier, it's also safer because the combustion process is far 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," said Ahmad, who has designed several natatoriums in the past.
Domestic hot water for the entire recreation center is handled with Lochinvar Corp., Lebanon, Tenn., boilers.
Since 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 recirculate natatorium air during unoccupied hours at a significantly reduced energy rate. The minimum exhaust fan operates only during occupied periods as opposed to a conventional economizer, which operates a full size 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, Ill., is capable of introducing 100 percent 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 to conventional economizer operation, the resultant annual energy savings from the 9,100-square-foot natatorium's dehumidifier is over $40,000 annually.
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, Ill., and general contractor, Nicholas & Associates, Mt. Prospect, Ill. The synergy between the HVAC design and the architecture assured the building orientation of windows on the South, West, and East sides that promotes more solar gain in the winter and less in the summer months. Consequently the building orientation resulted in a smaller-sized dehumidifier compared to 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 versus a drop-ceiling design subliminally give swimmers the more open feeling of swimming outside rather than in an enclosed box.
Collaboration between the architect and engineer is also evident in the rooftop dehumidifier positioning, which is in close proximity to the six-foot-higher outside wall of the natatorium. Instead of a large amount of costly fabrication and installation labor associated with rooftop equipment, the rooftop ductwork merely projects five feet 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 for smaller horsepower motor/blowers that saved approximately 5 percent in air distribution operational costs.
Doonan's value engineering contribution was replacing the round spiral aluminum duct specification with fabric duct, thus saving $35,000 in ductwork labor and materials. Additional savings will come from the fact that the 30-inch diameter fabric doesn't need protective epoxy paint coatings, which is a direct construction cost as well as long-term maintenance savings. Additionally, Avery stands to gain long-term IAQ benefits and other reduced maintenance costs because fabric duct doesn't attract condensation, which can proliferate biological contaminants. If the duct needs cleaning, it's designed to be disassembled and commercially laundered.
The 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, Okla., 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 Carrier, Syracuse, N.Y., 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 is expected to eventually payoff in higher 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."
Publication date: 05/08/2006