Canadian Consulting Engineer

simple advances

August 1, 1999
By Rich Janecky

breton, Banville and Associates (BBA) is a mid-size Quebec engineering firm that specializes in the latest energy and control systems. BBA has helped upgrade a wide range of businesses, from mining co...

breton, Banville and Associates (BBA) is a mid-size Quebec engineering firm that specializes in the latest energy and control systems. BBA has helped upgrade a wide range of businesses, from mining companies to private and public utilities, so it is only fitting that a company known for its cutting-edge technology uses an equally progressive approach in the design of its new corporate headquarters in Mont Saint-Hilaire, Quebec. The prime goal for the new 4,645-m2 facility was to give the employees a more comfortable place to work by addressing indoor air quality, lighting and sound-proofing. The firm also wanted all building systems including HVAC, lighting, security and fire prevention unified so that one person can monitor and modify them through a single-user interface.

Working with few design constraints, the consulting engineers on the project, Concept R Engineering, and the BBA design team completed a project that represents significant advancements in the use of standard, off-the-shelf equipment with a unique set of systems and controls.

Reservoir heating and cooling

Located directly beneath the building is a 200,000-litre mitigated-water reservoir that acts as a thermal storage unit. Energy generated at the core of the building by its occupants, lighting and office equipment is transferred to the reservoir and saved for future use. The reservoir is kept between 60 and 90 Fahrenheit for optimal efficiency. During the winter months, when the reservoir’s energy is drained, an auxiliary natural gas-fired boiler is activated to maintain the reservoir’s minimum 60F temperature. Ronald Gagnon of Concept R says the boiler has been fired up only three times since BBA employees began moving into the building last December. The only additional heating sources are small 5 kW heaters located by the main entrance and the emergency staircase.

During the summer months, the system operates in reverse. During the day, the reservoir stores the heat generated within the building. At night, when peak demand is at its lowest, the system’s cooling tower kicks in. By the time the BBA employees begin to arrive at work, the reservoir is back down to 60F. Gagnon explains that on the cooling side, the system has enough inertia to operate for 10 hours before the reservoir heats past 90. Even on the warmest summer days the cooling tower does not kick in until the evening.

Heating and cooling is evenly distributed through a network made up of 42 water-source heat pumps, linked to the reservoir with stainless steel piping. The schedule 10 stainless steel piping is more expensive than its standard mild steel schedule 40 counterparts, but the cost of using stainless steel is offset because it is easier to work with; simple clamps are all that are needed to fasten the stainless steel pipes together.

Improving the system’s reliability was the real motivation behind choosing stainless steel. The network is a fully enclosed system and the water in the reservoir is the same water that will supply the heat pumps for the building’s entire life. The stainless steel piping reduces the potential for corrosion and also prevents scale build-up within the heat exchangers.

To further improve the system’s reliability, the design team decided on modifying the project’s off-the-shelf heat pumps. The heat pumps’ water-regulating valves that work on compressor head pressure were replaced with conventional balancing valves, ensuring a constant flow of water is supplied to the heat pumps 24 hours a day. Gagnon admits that some efficiency is sacrificed with this approach. Nonetheless, he defends the decision. “With the variable valves, pressure is not going to be equal throughout the network. If you start changing operating pressure you won’t have the same distribution all the time.”

Indoor air quality was addressed through a centralized network that features only one variable-valve latent thermal wheel that operates at 75% efficiency. This unit is the building’s sole source for its entire fresh air demands. Concept R is monitoring the CO2 levels on both floors and is constantly re-adjusting the volumes according to the building’s scheduling and contamination levels. Gagnon says the building averages only 550 ppm of CO2, a figure well below their 800-ppm target.

The building’s energy performance and indoor environment are further improved with the attention awarded to the building envelope. Triple-paned windows, maximized on the southern exposure, make the most of available daylight, while additional insulation in the walls and roof helps to retain heat.

Again the design team wanted to keep materials and techniques for the building envelope conventional, but Gagnon says that within these limited constraints the team was still able to design a building envelope that was effective at keeping the inside of the building comfortable.

Altogether the additional insulation, high-performance windows and the particular attention to detail reduced the cooling capacity by 36 tons. With that kind of savings the team could offset the $67,000 it cost for the higher-quality material by downsizing the equipment. Concept R estimates that downsizing equipment specifications saved the project $37,000.

Integrated controls

The BBA building is highly automated. Enter a conference room, for example, and the lights automatically come on and you hear the ventilation power up. All personnel have their own security profiiles that grant them access to some rooms and not others.

Engineering the building controls so that they all — fire, security, lighting, and HVAC — work together smoothly through a single-user interface is perhaps the design team’s greatest accomplishment, especially considering the tight deadlines they had to work under. (BBA fast-tracked the project and requested that the new headquarters be built, occupied and operational in just eight months.)

Again, the design team was directed to stick with standard equipment. But equipment regularly available in the market place does not always communicate easily with equipment from other manufacturers. For example, the design team managed to use a single set of motion sensors to control the lighting, HVAC, and security systems, but they had to use software interfaces to make them work the way the client desired.

To cut down on the software translation problems, the design team opted for a Johnson N2 platform. Overall the equipment did work together transparently and efficiently, but Gagnon explains that to perform high level operations they still have to refer to each individual system. “You don’t have full transparency across the line,” he says. “With the Triatek lighting system we have the Triatek software. We don’t use it in normal operating, but if we want to exchange some sequences in the Triatek board we can download it using a PC.”

All Direct Digital Control (DDC) manufacturers have canned functions (for example, proportional and integral differential (PID) loops for reaction and anticipation), but the design team was looking for sophisticated sequences so they had to develop their own. Gagnon says that the programming became very elaborate. They have to use heavy sequences that use way more processor time than with canned functions.

Programming the HVAC system was another hurdle. Most of the loops were not designed for this kind of application. The worst part control-wise was the cooling tower and heating system. Working off-line at different periods, and shedding load-in-time, were functions that no available sequence could handle. So the sequence for this had to be written from scratch.

Gagnon admits that developing the controls was a trying experience for most members of the design team. But he adds that it would have been more difficult and taken much longer if they didn’t use the team approach involving all the consultants — engineers, architects and the interior designers — on the project.

Engineering the controls for the new BBA headquarters has taken on a life of its own. Concept R is still working on additional sequences that will further reduce peak demand. Gagnon
expects that the additional sequences will reduce peak demand by 25 to 30 kW.

From a performance standpoint, the additional design and engineering features are a success. The upgraded heating and environmental systems are estimated to save the company approximately $40,000 dollars per year. When compared to conventionally built structures in the region, the payback period on the additional investment translates into 3.3 years.

With the combined high-performance building envelope and an elaborate system of sensors and controls, the building uses 39.1% less energy than if it was built to the Model National Energy Code for Buildings standards. The building’s exceptional energy performance also qualifies for additional funding from Natural Resources Canada’s Commercial Building Incentive Program — a program initiated to cultivate better building practices within Canada. According to the government program’s formula, The BBA headquarters qualified for a $40,861 incentive.

BBA is happy about what they accomplished with their new corporate headquarters. In fact, they are already considering using the same approach for their next building project which will soon be erected across the street from their new headquarters. CCE

Rich Janecky is an Ottawa writer.


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