By Bronwen Parsons
Symphony of Design: Jasper Place LibraryBuildings Building Mechanical & Electrical (HVAC) Systems Building Structure
Achieving a tight integration with the architecture was one of the most memorable achievements in this project," says Chad Musselwhite, P.Eng., of Williams Engineering Canada. "In the open areas of the library there are no heating, ventilation,...
Achieving a tight integration with the architecture was one of the most memorable achievements in this project,” says Chad Musselwhite, P.Eng., of Williams Engineering Canada. “In the open areas of the library there are no heating, ventilation, controls, lighting, power or anything on the underside of the concrete ceiling. It’s completely open as far as the aesthetics go, which is something the architects wanted to achieve and which was a challenge for us as mechanical-electrical engineers.”
Musselwhite was project manager with Williams Engineering (WEC) for the Jasper Place Library built in Edmonton last year. The 1,394-m2 (15,000 sq.ft.) branch of the Edmonton Public Library, located at 156 Street NW and 90th Avenue, replaced a smaller predecessor built on the site in 1961. Despite a renovation in 1988, the older structure could not serve the library’s evolving needs. “There was an analysis done for adding to the old facility and renovating it, but in the end a complete rebuild was required,” explains Musselwhite.
The new library exerts a striking presence in the neighbourhood. Its large undulating concrete roof “floats” over a completely glazed front wall. The roof has deep overhangs, and below it projects a rectangular solid volume marking the entrance. Across the upper half of the wall’s glazed front is a series of horizontal sunshades.
Inside is a large, bright open public area. There are areas for book collections, children’s activities, quiet study areas, and computer stations. There’s also a terraced informal seating area. Beyond this open space are the more enclosed administration areas and a community multi-purpose room.
Expressive and functional
If the architecture of the library is expressive, it is also functional. The forms not only create an open and light-filled interior, but also play a role in the building’s ventilation and cooling systems.
The integration of architecture and function is thanks to the collaborative approach taken by Dub Architects, Hughes Condon Marler Architects, Fast + Epp structural engineers, and WEC as mechanical-electrical engineers. The design process started with a design charette in which library and city department staff also participated.
The result is a building that has 90 per cent of its spaces lit by daylight, that can rely on natural ventilation for certain periods of the year, and that according to computer models uses 51 per cent of the energy used by a standard equivalent building designed to Canada’s National Energy Code for Buildings. The building is mandated to be certified as LEED Silver, but it is still under review by the Canada Green Building Council, and the designers are hoping it will be certified as LEED Gold.
Access flooring and displacement
ventilation: a good combination
The last thing the architects wanted was to have the dramatic exposed concrete roof in the main space cluttered with mechanical and electrical equipment.
The solution was to use an 18″ high access flooring system. Into that raised floor space is channelled all the electrical and communications cabling. The access floor also distributes the ventilation air through diffusers.
The system delivers the air at low velocity which allows the air to spread out along the floor. The air rises as it warms and is displaced by fresh air entering behind it. This non-turbulent air flow gathers both waste heat and contaminants generated by people and computers and pushes the stale air upwards and away from the occupied space. WEC’s description calls this a “naturally balancing and highly effective” process that achieves high indoor air quality “with the least expenditure of mechanical energy.”
By contrast says WEC: “Traditional systems focus on creating a well-mixed volume of air within a space and in doing so trap the waste heat in the occupied zone, rather than letting it evict itself from the cooling equation.”
Operable windows scoop out stale air
Edmonton generally has a mild climate in the summer, spring and fall, so when outside temperatures are between 18-24°C most of the mechanical ventilation systems for the large open area can be turned off altogether. At these times the space can be naturally ventilated with air entering from low operable windows on the north end of the space, then rising naturally to be swept upwards along the sloping roof. The air exits through the high south wall via operable windows. Even when the days are too hot and mechanical air-conditioning is required, the windows automatically open at night to allow the building to be naturally cooled.
“This is the other benefit of integrating the systems with the architecture,” says Musselwhite. “Displacement ventilation works really well with access flooring, but it also works well with high ceilings. It’s really neat how all these things are working together. That’s not always the case. Sometimes there is a trade-off where the mechanical and electrical systems have to make a building livable where it might not be so otherwise, where systems are working to counteract the effects of one another rather than working in the same direction.”
Overhangs and heat loads
The large expanse of south glazing creates challenges due to solar heat gains, so the roof has a deep overhang to provide shade in summer when the sun is at its peak. The external sunshades are designed for the same purpose. WEC did an analysis for the architects to determine their size. The goal again was “to minimize the heat load rather than compensating for it by maximizing the size of the chiller equipment.”
The exposed concrete roof not only looks dramatic, but also plays a useful role in balancing the interior temperature swings. In an age-old system, the concrete acts as a thermal mass, soaking up and storing either hot or cold energy and taking the edge off any sharp shifts in the outdoor temperature, which are common in Edmonton.
For cooling the ancillary spaces and for times when it is so hot outside that mechanical systems are required to cool the main space, there is an air cooled chiller and a single make-up air unit in the mechanical room. It has a heat recovery wheel, variable frequency drives and MERV 13 air filtration. Sensors measuring carbon dioxide and occupancy levels help to make the system operate as efficiently as possible.
Heating in the building is provided by three modulating, high-efficiency condensing natural gas boilers. The open area has recessed low-temperature convection heaters around the perimeter. These prevent condensation developing on the inside surface of the glass and protect people sitting in those zones from cold downdrafts.
Controls monitored by the city
The building management system (BMS) that orchestrates all these systems is based on a BACnet protocol, which is open and non-proprietary. What’s unusual is that the BMS ties into a wider campus network that is operated and controlled centrally by the City of Edmonton (see story, p. 21).
“The City of Edmonton operations and maintenance people can look into the facility over the internet and see how everything is running. They can manipulate the systems to address any issues that occupants are having,” explains Musselwhite.
“What we design has to be compatible with the city-wide system. There is a short list of vendors that have been preapproved,” he says. “Having that consistent approach allows the city to have energy measurement and verification software that can extract trends for this building and for their building portfolio as a whole.”
Clean ceiling, indirect lighting
The architects’ desire to have the concrete ceiling unencumbered by equipment meant conventional lighting was out. “From the electrical side there were challenges,” says Musselwhite. “So we had to work with the architects to find a location for the lights on the perimeter walls
and columns.” These lights shine upwards to spread indirect ambient light. There are also task lights integrated into bookshelves and furniture “so you have the light where you need it,” he says. The maximum energy consumption is 10 W/sq.m.
A fire sprinkler system would have obscured the ceiling lines, but the architect and code consultant were able to show that occupant safety is achieved in other ways.
The building has conventional security systems, including camera surveillance monitoring. Emergency lighting is provided in the general lighting, using an emergency lighting inverter. This eliminates the need for battery packs and emergency light heads on the walls and ceilings.
After careful analysis it was decided that a rainwater recovery cistern and a grey-use water re-use system were too costly and that the savings could be applied more usefully to other “green” elements. Nonetheless, thanks to its low-flow plumbing fixtures the building uses only 52 per cent of the potable water that an equivalent standard building would use.
Another green feature is a charging station for electric vehicles in the parking lot.
A library must be flexible
“A part of sustainability that’s not talked about much is that if a building is very flexible it can be a useful building for much longer,” points out Musselwhite. A building that is durable means an efficient and more sustainable use of the earth’s material resources.
The access floor brought benefits in this durability aspect as well. The electrical, computer and other cables it contains are modular and can be easily changed as needed. “Using the access floor worked out not just for our [electrical and mechanical] systems, but for the flexibility of the building in the long term,” says Musselwhite. “Today libraries need to adapt to many different space functions from one day to the next. They are rapidly changing in terms of whether they have books or more digital forms of information exchange. Since we can’t predict what will be required of a library in the future, the more adaptable and flexible the building is, the longer it can serve and function.” cce