The Reginald-J.P.-Dawson Library, Montreal
The vertical open space design of the new building from basement to roof provides natural light to the heart of the library. The existing building, on the left, is now flooded with natural light through the addition.
The Reginald-J.P.-Dawson Library, located in the heart of the Town of Mount Royal in Montreal, went from being a place to simply borrow books to providing the local community with a cozy venue where it is possible to nourish the mind, get some respite, relax, recharge, revitalize, and be inspired. Moreover, it was done in harmony with respect to the original heritage building, and in continuity with the city’s lush green spaces. The extension of the building was designed to be resilient and sustainable.
These exemplary objectives were set during the integrated design phase, where the city invited the architect and engineer to study the project and determine the most favorable development plan.
The new construction, which extends the existing library, is mainly dedicated to reading rooms and offices. It consists of a basement, a ground level, a mezzanine, and first floor, covering an overall area of 13,313 ft2. The existing portion of the building was 21,200 ft2. This multi-level design floats overtop the public space, expressing itself vertically, in contrast to being spread out.
The unique bioclimatic design is reflected in various ways throughout the new building. Perhaps the most impressive proof of the eco-efficient concept is the fact that even though the library’s square footage expanded by 68% with the addition of the new building, the energy consumption increased by only 22%. When translated to the LEED certification criteria, the energy efficiency earned 19 points, the highest attainable LEED score for energy performance optimization.
The energy model, which compared the new building to an ASHRAE/IESNA Standard 90.1-2007 baseline building, showed its energy consumption to be 52.91% lower, and its energy cost 57.59% lower. Some elements that contribute to this performance are the geothermal wells, the radiant floor, a hybrid ventilation system (mechanical and natural), heat recovery ventilation units, very low energy consumption daylighting controlled lights and movement sensors, CO2 sensors, as well as a highly efficient building envelope.
More specifically, the heating/cooling system relies on three heat pumps. In cooling mode, the energy retrieved from the various spaces is transferred to the hot manifold, reducing the energy required to produce hot water. This configuration is most effective during mid-seasons, absorbing the hot and cold water demand fluctuations.
Inversely, in heating mode, the hot manifold can transfer energy from the floor to the geothermal wells. Hot water is distributed to the radiant floors throughout the new building. To meet the building’s energy needs, seven new wells were added to the existing six.
Another contribution to the bioclimatic concept comes from the coupling of the radiant floor with a ventilation system equipped with a heat recovery ventilator, through which the heating energy of the building is retrieved. In winter this system, with a 70% latent and sensible heat recovery efficiency from exhaust air, allows for fresh air preheating.
With the perspective of improving both energetic yield and overall comfort, a hybrid ventilation system combining mechanical and natural systems allows, in given conditions, to ventilate and cool without using energy. This is made possible by the vertical open space design in the center of the new building, from basement to roof. Not only does this space invite natural light to the heart of the library, but it also creates a temperature gradient, or stack effect, pulling the air from the lower level opened windows to the windows at the highest point of the staircase near the roof.
When exterior conditions allow for it, natural ventilation is prioritized by the centralized controls of the mechanical equipment (dampers, motorized valves and windows, ventilators, temperature/pressure/humidity setpoints, boilers, heat pumps, etc.) through activation of strategically placed motorized windows in the building perimeter. Once the windows are opened, air naturally flows through the building.
Indoor Air Quality and Thermal Comfort
To ensure the best air quality, the heat recovery ventilators are fitted with high-efficiency filters, and CO2 sensors are installed in strategic areas to regulate the required fresh air intake. The relative humidity is maintained by a vapor humidifier inserted in the fresh air ducts, as well as humidity sensors installed strategically in the building.
The humidity and temperature setpoints were set using ASHRAE Standard 55-2004. One challenge met by the design team was how to choose the clo level in the spaces since the employees are dressed for a normal office type workday, while the occupants may be arriving in the library wearing winter jackets, for example. In the end, the owner and the design team decided to go with the values closest to the level of the employees since visitors always have the option to remove clothing, and the employees are using the space all day.
Fresh air renewal and distribution is optimized when exterior conditions allow the hybrid ventilation system to be activated.
Another strategy implemented to improve air quality and occupant comfort is displacement ventilation. Many zones within the library have very high ceilings and many occupants. These zones are ventilated through displacement, supplying air at low speed near the floor. Two distinct zones are created: the lower level, where the occupants are, is the stratified zone; up higher is the mixing zone. With this type of ventilation, the free-cooling period can be extended.
The connection to nature and to the outdoors is present even in a completely urban setting.
© Bénédicte Brocard
With the radiant hot water floor as the heating source, the risk of combining and redistributing various odors in the rooms is completely avoided since no air is transferred from one room to another as with a heat through ventilation air system.
All of the airflow rates were calculated using ASHRAE Standard 62.1-2007 and were validated through the LEED certification process. An Ez value of 1.0 was used, since only air cooler than or at the same temperature as the room is ever supplied through the ceiling with radiant floor heating.
Furthermore, as mentioned below in the Environmental Impact section, materials were selected based on their low emission of volatile organic compounds.
If taken individually, most of the technologies in place in the building might not seem exceptional in and of themselves. However, when looked at as a whole, the library is an entirely innovative building.
The idea to use existing equipment and enhance its use is not only ecological, but a novel approach. The engineers used equipment that was not working to its full potential and enhanced the system by adding geothermal wells and connecting new heat pumps to the network, resulting in a comfortable and energy-efficient building.
Natural ventilation is rarely seen in a library since there are concerns with humidity levels in an environment with books. By adding the proper controls to the windows and going through a rigorous commissioning process, all the required setpoints are maintained. Natural ventilation is available many hours throughout the year.
By using an integrated design process, the building geometry was able to accommodate the engineering requirements (central basement to roof opening), while also providing a space that promotes tranquility and light, an ideal setting for reading and learning.
Operation and Maintenance
The maintenance personnel have local and remote access to a building management system (BMS), which integrates all electro-mechanical equipment. Through the BMS, they can fully optimize the balance between environmental conditions, energy consumption, and operational needs. Furthermore, the alarm signals are sent to the operators via emails and telephone messages, and they include the level of urgency tied with the action to be taken.
Start-up was carried out with ease, even though it involved the integration of the existing building systems into the new BMS. The heat pumps were intensively commissioned to optimize setpoints with respect to the new conception.
The commissioning process not only allowed for a smooth start-up of the new equipment, but also helped the O&M staff understand the importance of continuous maintenance such as filter changes to maintain equipment efficiency.
Commissioning of natural ventilation required more time, testing different enthalpies to get the best compromise between mechanical and natural ventilation. The process ensured that the displacement ventilation was adjusted to the occupants’ liking while maintaining the vertical temperature gradient within the setpoints calculated with Standard 55-2004.
A comparative study on energy/cost consumption was carried out after one year of occupation. The study compared pre-renovation (2008–09) consumptions and post-renovation consumptions (2013–14), accounting for outdoor temperatures. The study found a cost increase of 36% and energy increase of 41%. On the natural gas portion, there was a reduction of gas costs of 40% and gas consumption of 53%. The result was a total energy cost increase of 31% and energy consumption of 22%, for a building that is 68% bigger in size.
Figure 2 shows energy consumption for 2015. In 2014, the total energy consumption was 4,508 m3 or 162 MBtu at a cost of $1,815.
The electrical consumption for the same year was 901,951 kWh or 3,077 MBtu at a cost of $66,312.
The total energy consumption for the building is 3,239 MBtu, which equals 152 kBtu/ft2.
Even though part of the existing building was conserved architecturally, those mechanical and electrical components were part of the renovation. According to RS Means Square Foot Costs 2014, the electrical and mechanical costs for a library are $70/ft2. The total existing building square footage is 21,200, which equals $1,484,000. The total project cost for mechanical and electrical was $1.6 million, for an additional cost of $116,000.
The energy model predicted an energy cost savings of 57%, which can be assumed for the existing building as well as the new construction for a cost savings of $39,000. This represents a return on investment of three years.
It is often said that the most ecological building is the existing building. This is yet another way in which the library stands out. It was not transformed through a demolition/construction process, but rather by the addition of a new LEED Gold extension, which is harmoniously integrated to the existing heritage building. Furthermore, this transformation allowed the existing portion of the building to reclaim its original cachet.
When compared to a reference building using gas with an 80% efficiency, we calculate savings of 653 MBtu, which translates in equivalent CO2 reduction of 35 tons.
Efficient water management is also a predominant preoccupation in the new building. The plumbing fixtures were selected to reduce the building’s water consumption by 40.1% (based on LEED calculations). Outside, the green roof, terraced garden, as well as the landscaping are all composed of native and adapted plants, which are drought-resistant and require no irrigation.
The construction materials were carefully selected following strict criteria. Paints, coatings, adhesives, and sealants were chosen based on their low emission of volatile organic compounds. The entirety of wood used in the new building was Forest Stewardship Certified. Thirty percent of the construction materials were of regional provenance and 12% contained recycled materials.
Other environmental initiatives rewarded in the LEED certification include designing lighting to reduce exterior light pollution, maximizing green spaces, no parking space, and remarkable access to public transportation, which surpasses the exemplary double transit ridership defined in the LEED manual.
The Town of Mount Royal is renowned for its abundance of trees and delightful green spaces. Building in continuity with this already rich natural landscape helps support biodiversity health and survival. Healthy biodiversity also helps prevent the establishment of invasive plants. Additionally, library users also benefit from the landscape, for as they move through the new building, they remain in constant visual contact with the outdoors, whether it is on the ground level gardens, views on the green rooftop, or the terraced garden.
The Reginald-J.P.-Dawson municipal library is a model to follow on so many levels, from resource optimization to reduction of ecological footprint, economical strategy, and valorization of built heritage. It is also a model that brings pride and a sense of community to the citizens of the Town of Mount Royal.
About the Authors
Martin Roy, LEED Fellow, is president, Nancy Picard, LEED BD+C, is director of LEED certification services, and Lianne Cockerton, LEED BD+C, is a mechanical engineer at Martin Roy et Associés, Deux-Montagnes, Quebec, Canada. •