The background

Wulf Recreation Center in Colorado needed energy-saving improvements. Monitoring retrofit projects can sometimes be a challenge, as delivering on promise is not easy. However, the energy performance contract by the Golden, Colorado offices of McKinstry, Seattle, Washington, guaranteed a 32% reduction in energy expenditures amounting to more than $18,000 annually. Thus, the contract took out the guesswork of the return-on-investment for the 40,000-square-foot Wulf Recreation Center’s $540,000 renovation.

Case study

Aim:

Reducing energy consumption and thereby reducing energy costs was the prime focus of the recreation centre’s retrofit project. Although the recreation centre includes a gym, gymnastics room, weight/cardio room, racquetball courts, child care, dance studio and other spaces, the pool is the centre’s anchor activity hub, because it serves the local high school and community for both competitive and family recreational swimming.

Method employed – sustainable initiatives:

McKinstry, which was led by Steve Ruby, Project Director and Caroline F Traube, PE, Energy Engineer, functioned as the energy service company (ESCO) on the project. The seven-year energy performance contract is using a measurement and verification process overseen by McKinstry’s Jaymes McMullin, Performance Assurance Specialist.

Based on a pre-construction energy audit completed during the summer and fall of 2011, McKinstry’s recently completed improvements guarantee an annual reduction of 109,000 kWh of electricity and 18,804 therms of natural gas, which equates to cuts of Wulf’s carbon dioxide emissions by 182 metric tonnes.

Cutting HVAC operational costs:

Integral to the energy performance contract’s savings was the replacement of two 40-year-old 100% outdoor air HVAC systems that controlled the 7,000-square-foot pool space’s temperature and relative humidity (RH). McKinstry and installing mechanical contractor, Murphy Co, Denver, replaced the system with two 6,500-cfm NV Series indoor pool ventilation units manufactured by Seresco USA, Decatur, Georgia, with less than a two-day downtime.

Equally important as the short downtime was the minimum of $4,995 in operational savings and 12,704 in reduced therms annually that the new system would provide versus the original gas-fired make-up air systems.

The NV Series uses several new technologies that include heat recovery, direct drive fans, an on-board microprocessor controller and other energy-efficient features. Unlike the original supply/exhaust system, heat from the space’s exhaust air is now recovered via a glycol run around loop (GRAL) for pre-heating outdoor air. Using the recovered heating energy, versus gas-fired equipment to help raise outdoor air temperatures from 0°F to 45°F reduces heating costs significantly. After maximising the pre-heating potential, the space’s 82°F set point temperature is completed through the NV Series units’ on-board gas-fired heaters.

The HVAC system’s dedicated duty, direct drive fans also reduce fan power consumption versus the old system’s belt-driven design, which is estimated to be as much as15% in typical application comparisons. Combined with variable speed controls that help tailor the ventilation operation to occupancy rates, the fans save significant amounts of fan energy versus the original units’ 1970’s fan technology.

Other positive outcomes:

McKinstry also specified an optional purge fan feature. Instead of the typical mix of outdoor and re-circulated air during common operation, the 100% outdoor air purge fan mode can complete a total pool space air change in an adjustable eight to 15 minutes. This is a strategic Indoor Air Quality benefit in the event of rising CO2 levels during heavily attended swimming competitions or in the case of excessive chemical odours during and after water shock treatments affect.

Another advantage of the new HVAC technology is its use of outdoor air modulating controls. The units don’t have a mechanical refrigeration circuit for dehumidification or space cooling, but instead use free cooling from Colorado’s mountainous climate, which is inherently dry and cool nine to 10 months of the year. By monitoring indoor and outdoor air conditions precisely, only the required amount of outdoor air is introduced to maintain the best possible pool space IAQ, save energy and comply with codes.

Before these controls were developed by the HVAC industry, natatorium ventilation systems typically provided more cool outdoor air than necessary during the winter, which potentially resulted in substandard RH levels. Low RH levels typically create uncomfortable chilling effect on wet skin.

A critical control feature of the indoor pool ventilation system is an on-board, Ethernet-based microprocessor that senses, tracks and transfers daily machine operating statistics via Seresco’s proprietary WebSentry system to the factory for daily monitoring and recording. The system, which senses compressor liquid and suction pressures, temperature, space humidity, outdoor conditions and dozens of other parameters, also sends operational alarms via email or telephone. Besides factory technicians, other responsible parties, such as McKinstry’s Josh Harwood, Programme Manager for commissioning services, and Ellen O’Connor, Manager of Recreation and the Wulf Project’s Team Leader for Evergreen Park & Recreation District (EPRD), Evergreen, Colorado, can receive email alarms and review real-time data from a computer or smartphone. This eliminates the possibility of a machine operating inefficiently for months between annual service calls, which can raise energy costs.

Since Wulf’s budget didn’t allow for the purchase of a digital building automation system, McKinstry used Hobo data loggers by Onset, Bourne, Massachusetts, to perform its pre-construction energy audit throughout the building. During the subsequent performance review, McKinstry took advantage of the WebSentry, which comes free from the manufacturer on all its equipment, and its ability to sense, track and record real time and historical data of the two indoor pool ventilation units.

Another major source of energy savings was converting the building’s mix of T-12 fluorescent, metal halide and high-pressure sodium light fixtures to a combination of more efficient T-8 and T-5 lamps manufactured by Philips Lighting, Cleveland, or Osram Sylvania, Danvers, Massachusetts. Wulf’s lighting is also now controlled more efficiently with occupancy sensors by Sensor Switch, Wallingford, Connecticut.

McKinstry also replaced old stand-alone room thermostats with a Viconics Technologies, Saint-Leonard, Quebec, networked, web-interfaced thermostat system that allows the facility manager to set schedules and temperatures from a single source dashboard and minimises unauthorised tampering.

Insulation was also installed in several room additions that had been built with only concrete block walls. The insulation improved the walls from an R-2 to R-10 rating and consisted of two-inch-thick rigid wallboard insulation by Dow Building Solutions, Midland, Michigan, and EcoBatt roof insulation by Knauf Insulation GmbH, Shelbyville, Indiana.

Conclusion

The Wulf Recreation Center in Colorado, which needed today’s new proven technology, including a new energy-saving indoor pool ventilation unit, lighting, digital controls and other upgrades, can save significant operational and energy costs.

The Wulf upgrades will not only save energy and money, but also improve IAQ and reduce EPRD’s carbon footprint. Annual utility savings combined with a $15,300 rebate from the Colorado utility Xcel Energy will deliver an 18-year payback for Colorado taxpayers.