©2014 This excerpt taken from the article of the same name which appeared in ASHRAE Journal, vol. 56, no. 4, April 2014.
By Jacques Lagacé, Member ASHRAE
About the Author
Jacques Lagacé is innovation vice president at Bouthillette Parizeau in Montreal
La Maison du Développement Durable (MDD) wished to make its Centre for Sustainable Development a model of sustainable design, by pushing sustainability boundaries, and aiming for a Platinum LEED certification rating. Built on a 14,900 ft2 (1384 m2) confined land lot in downtown Montreal, the five-story building has a total floor area of 68,450 ft2 (6359 m2) and an average glazed area of 34%. It houses the offices of eight social and environmental organizations including Équiterre, a kindergarten, and a restaurant, for an overall occupant population of more than 200 adults and 72 children.
The building was designed using an integrated design process. Building professionals, experts and observers shared their experience and expertise in order to develop the design, justify choices, and analyze every facet of each solution. The specialists questioned all suggested ideas from their own unique perspectives.
Performing energy balance analyses and energy simulations software, helped the design team optimize the mechanical and electrical infrastructure and the envelope performance to reduce energy consumption, capital costs, and operating and maintenance costs.
To reduce the environmental impact of the building, geothermal energy is used to satisfy 100% of heating and cooling needs. The results of test wells were used to characterize the ground and define the thermal conductivity, which helped to optimize the number of wells required and eliminate redundancy and unjustified cost investment. Because the amount of land area was small, the 28 geothermal wells were drilled directly underneath the building to a depth of 500 ft (152 m), an equivalent of 4 tons (14 kW) per well.
Each geothermal well is independent from the others to minimize negative impacts on the capacity of the system in the event of a failure of one of the wells. The geothermal system performs at its maximum throughout the year, because the equilibrium has been carefully calculated.
During winter, energy is extracted from the ground to satisfy the heating needs of the building (equivalent to 728 MBH [213 kW]). A high-efficiency natural gas condensing boiler (750 MBH [220 kW], e=97%) is installed to be used only as a backup in case of geothermal failure or for extreme winter conditions.
In summer, air conditioning is provided solely by the geothermal heat pumps using R-410A refrigerant, totaling 113 tons (400 kW), with an average 3.93 COP. A conventional water tower is not require, reducing infrastructure and maintenance costs, physical footprint installation, potable domestic water consumption, chemical treatment, as well as improving overall architectural aesthetics.
The building has two supply ventilation systems: one for the office spaces and the kindergarten, which have similar schedules and are supplied at 13,000 cfm (6135 L/s). The second system serves only the ground floor, which is continuously in use with 10,550 cfm (4979 L/s). The 9,800 cfm (4625 L/s) outdoor air volume is processed by a dedicated outdoor air system (DOAS) whose rate varies from a minimum that balances the general exhaust to a maximum peak flow to compensate kitchen hood exhaust that operates at variable speed with infrared detection (reducing energy consumption of treated air). To further maximize the energy recovery, a heat recovery cassette type (average year-round at ±68%, peak at 92%) was installed between outdoor airflow and general air exhausts.
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