By By Chantale Bourdages, ing. and Olivier Brodeur, ing. Dessau
Symbol of SustainabilityBuildings Building Mechanical & Electrical (HVAC) Systems
As an ecologically responsible pioneer in sustainable building design, the new Cartierville YMCA in Montreal is a truly 21st-century expression of the organization’s philanthropic values and mission. Open since April 2010, the...
As an ecologically responsible pioneer in sustainable building design, the new Cartierville YMCA in Montreal is a truly 21st-century expression of the organization’s philanthropic values and mission. Open since April 2010, the 88,000-sq.ft. construction, located about 15 kilometres northwest of downtown Montreal, offers aquatic, sports and recreation facilities such as a semi-Olympic pool and an indoor jogging track. It also has multifunctional rooms and a daycare.
Due to their elevated hot water consumption for pools and showers, as well as their need for extra air-conditioning and dehumidification, recreation facilities tend to have lofty energy bills. Engineering-construction firm Dessau was mandated to carry out the energy efficient HVAC design that would become a focal point of this environmentally friendly building. By creatively combining clean renewable geothermal energy and clever heat recovery systems, the mechanical engineering team was able to craft a self-financing project that is designed to save the building owner almost $200,000 a year and use 50% less energy than a standard building of its type.
The building was made possible due to an innovative partnership between the Ministère de l’Éducation, du Loisir et du Sport du Québec (MELS), the city of Montreal, the borough of Ahuntsic-Cartierville and the YMCA.
Energy Modelling Using DOE2
Quebec’s extreme winter climate presents challenges for designers of efficient building systems and tends to complicate energy management. To meet these challenges, the design team created a model of the building and its electromechanical systems using DOE2.1e simulation software to accurately analyze the building’s peak and partial loads.
The software simultaneously takes into account weather data, building envelope parameters and complex building HVAC system interactions that are almost impossible to estimate using traditional calculation methods.
Subsequently, energy simulation models were used to demonstrate the energy savings and cost-effectiveness of different scenarios. These helped determine that integrating geothermal energy with heat recovery equipment was well worth the initial investment. Data provided by the building simulations proved to be essential for designing and sizing the geothermal and recovery equipment.
Geothermal Exchanger Optimized
to 30% of Peak Load
Thermal comfort is maintained throughout the building with 21 water-to-air heat pumps, while three water-to-water heat pumps were installed to meet the building’s significant hot water needs.
The building’s heat pumps are connected to a geothermal closed loop that substantially increases the performance of the equipment. Renewable ground source energy is ideal for extreme climates typical of regions in Canada. During winter, the geothermal loops draw heat that has been stored in the ground the previous summer. During warmer summer months the geothermal loops reject excess heat from the building and slowly recharge the ground for the upcoming winter. This alternating cycle of heat absorption and storage works well in regions with extreme seasonal temperature variations like Québec.
Unfortunately, excavation and materials for geothermal ground exchangers are quite costly. Furthermore, because the average heating or cooling part load for a building in Quebec is generally under 50% of its peak load, heat pump efficiency is reduced considerably when sized to meet the building’s overall needs.
Taking these two factors into consideration, the design team for the YMCA decided to evaluate a cheaper auxiliary heating system — electric boilers – to supply extra heat during periods of intense cold. Energy simulation models helped pin down the percentage of the maximum capacity that should be ensured by the geothermal system. This optimal combination of systems made it possible to reduce the size of the geothermal exchanger to 30% of the design’s peak load, consequently keeping excavation and material costs to a minimum.
A blend of water and propylene glycol flows through 12 boreholes, each 450 ft. (137 m) deep, which were drilled and connected to the building’s water network. Furthermore, by downsizing heat pumps by 70% under the building’s peak load, the designers ensured that the equipment would work more hours at full capacity, therefore maximizing HVAC performance.
Flexible Water Networks for Recovering Heat
Deemed unusable, excess heat is often discarded even in the dead of winter by conventional HVAC systems using air condensers or cooling towers. In this case, however, by carefully analyzing the YMCA’s heating, cooling and humidification loads through simulation models, the designers were able to create a sophisticated multiple water network system that prioritizes heat recovery.
Having flexibility between water networks is a key element for fully recovering the building’s internal energy before tapping into the geothermal or grid equipment. For example, excess heat from the dehumidification processes and superfluous heat generated by the mechanical room equipment is salvaged to supply building space heating and hot water needs.
As well, an enthalpy wheel recovers sensible and latent heat that would usually be lost in the outgoing exhaust air and transfers it to the incoming fresh air, with an average efficiency of 75%.
By reducing the amount of energy wasted, the heat-recovery systems not only generate important energy savings, they also radically reduce the building’s heating and cooling loads, which enabled an initial downsizing of the related equipment.
Integrated Architectural Approach
By incorporating integrated architectural, engineering and urban design principles from frameworks such as LEED, Integrated Design Process, Community Design and Smart Growth, the Cartierville YMCA has become a pillar of sustainability in Montreal’s Ahuntsic-Cartierville district by contributing to its local social, economic and environmental development.
The architectural design, for example, incorporates an abundance of natural lighting, and it also includes a white roof. By improving solar reflectivity, the white roof reduces the building’s cooling needs as well as urban heat island effects. A water management system rations the building’s use of water resources, and the building’s landscape design focuses on providing urban green spaces for recreation and social gathering. Furthermore, by choosing a location that is highly accessible via public transit and integrating 110 bicycle parking spaces, the building encourages its patrons to use sustainable transport.
Lastly, the Cartierville YMCA’s environmentally conscious self-financed HVAC design spawns savings that help conserve energy and reduce greenhouse gases by 1,200 tons a year while promoting the financial feasibility and benefits of renewable energy.
If one of the YMCA’s mottos is Mens sana in corpore sano (a sound mind in a healthy body), the new Cartierville YMCA proves that the organization also endorses a more global vision, supporting the fact that human beings should have access to healthy buildings and communities as well. cce
Client-Owner: YMCAs of Québec
Mechanical-electrical: Dessau, Montreal (Olivier Brodeur, ing., Laurier Nichols, ing., Jean-Luc Thomassin, T.P.)
Architect: Daoust Lestage