Canadian Consulting Engineer

Buildings: Prairie Vision

August 1, 2012
By By Russell Lavitt, P.Eng. SMS Engineering Ltd.

When the Winnipeg Airports Authority decided to replace its outdated 1960s-era air terminal building, they chose Stantec Architecture and international architect César Pelli for the design. The resulting, $585-million, 51,000-m2 facility...

When the Winnipeg Airports Authority decided to replace its outdated 1960s-era air terminal building, they chose Stantec Architecture and international architect César Pelli for the design. The resulting, $585-million, 51,000-m2 facility opened in October 2011.

Named after the “father of Canadian commercial aviation,” the Winnipeg James Armstrong Richardson International Airport handles 3.4 million passengers per year and is the eighth busiest passenger airport in Canada. It is predicted that 4.1 million travellers per year will pass through its doors by 2015.

The architects’ vision was for a new terminal characterized by transparency, connectivity and an abundance of natural light.

SMS Engineering were the lead mechanical and electrical engineering designers and were instrumental in delivering a robust and energy-efficient building that performs over 50% better than the Model National Energy Code for Buildings. It is also the first free standing airport in Canada, and the second in North America, to undergo a LEED accreditation process. All this was accomplished in a location that has one of the most widely fluctuating climates in the world.

A giant fish bowl

The architects planned for an all-glass building, making it easy for travelers to find their way and allowing for an abundance of natural light.

However, a transparent 51,000-m2, three-storey, north facing structure enveloped by 500+ linear metres of glass presented an enormous mechanical design challenge. How do you efficiently heat and cool a giant fish bowl located on the windswept Canadian prairies?

The 55 skylights, atrium, many thousands of square metres of glass walls and numerous clerestory windows spill light into the terminal, but they can also be a source of solar gain, causing the building to heat up and making temperature control difficult in the summer.

Thermal and light studies revealed that wintertime solar energy could easily be absorbed into the building’s heating system and re-used. The challenge became how to provide enough cooling to counteract the heat generated from the summer sun.

The architects modified their original floor-to-ceiling, clear glass design by adding a ceramic bonded, fritted glass in the upper sections. Finned shades were also added to the curtain wall to “shadow” direct light at certain solar angles and help control solar energy from entering the building.

Harvesting solar gains in underfloor piping

To find a way to counteract the direct summertime solar gain to the floors, the engineers studied where the sun would enter the building throughout the day for each day of an entire year. With this it was possible to know where the most solar energy could be harvested. In these locations, flexible plastic tubing is embedded into the floors. Cool water runs through the tubes and absorbs the hot summertime sun, repurposing the energy elsewhere in the building. This process reduces the need to cool the building with treated air. The tubes also pipe the hot water needed for radiant floor heat in the winter.

During the cooling mode, sensors determine the dew point temperature of the air adjacent to the floor to prevent dangerous puddles forming on the tiled walking surfaces and water condensing on the carpeted floors.

During moderate outdoor winter temperatures, the radiant heat system can operate as designed, at a lower water temperature. When winter temperatures drop, the radiant floor system needs to operate near 60° C to generate enough heat to push through the carpeted floors to warm the space.

The problem for the designers was two-fold — where to get the additional heat and how to deliver it without compromising the integrity of the concrete floors, which when heated to high temperatures for long periods of time, would begin to deteriorate.

Most modern equipment produces heat at temperatures greatly beyond what was needed for the floors (82° C versus the required 60° C). Options such as adjusting the boiler’s temperature controls and cooling overheated water to the appropriate temperature were quickly eliminated. Cooling overheated water wastes energy and running boilers at lower temperatures would damage the units.

Heating cascade

Research revealed a product made in Montreal that would make the entire system work.

Traditional hot water boilers produce high temperature water (82° C) from the central utility building, which is pumped approximately 1,000 metres to the air terminal. Once in the terminal, the water is first pumped to high-temperature devices needing a high volume of hot water, like wall-mounted radiators and heaters located near entries.

Instead of directly returning this water to the boiler for reheating, as is done in most buildings, the heating system directs this nominally cooler water to the next stage of the cascade — the air handling system. The coils in the air handling system are designed to accept water from the radiators at a medium temperature and use it to heat the outside air. The temperature of the used water is lowered to near body temperature before finally it is pumped to the boiler plant. This water is too cool to be used as return water in the non-condensing boilers.

Squeezing heat from the boiler

In order to increase the overall efficiency of the boiler plant, the Montreal-made flue gas economizer unit (see photo p. 27) captures latent energy from the boiler exhaust so that it can boost the return boiler water temperature. An extraction fan draws the boiler exhaust into the unit, pushing it up and out the chimney of the central utility building, while a spray of water is simultaneously pushed down against the flow of the exhaust. The contact area between the exhaust and spray is increased by a packing of stainless steel rings.

Heat from the exhaust is transferred into the water spray. This heated water is then passed through a heat exchanger which is used to heat the low temperature water returning from the terminal building. This water is heated to above 60° C to ensure proper operation of the central utility boilers.

The flue gas condensing economizing unit used on the project also has a natural gas burner built in that allows it to act as an additional boiler. As a result, the unit is used as the primary heating source, due to its very high efficiency. The traditional boilers operate only when the building needs greater amounts of heat.

An airport has many spaces requiring constant cooling, including electrical rooms with large transformers, computer rooms, retail stores and restaurants. By combining the cascading heating system with an efficient condenser water loop, the designers were able to capture energy from these spaces and use it elsewhere in the building.

The end result is a heating plant for a 51,000-m2 building that is nominally above 95% seasonal efficiency.

The terminal building is primarily cooled by high-efficiency chillers located in the central utilities building. Chilled water is pumped to the terminal and fed to the air handling units and radiant floor (when in cooling mode). During shoulder seasons, or should the central chillers be off-line, two smaller chillers within the terminal building produce the necessary chilled water for smaller loads.

Air — only where needed

The air ventilation system services only the zones where people are present, leaving the remaining three-story high space alone.

Air handlers – some 20 units ranging from as small as 150 L/s of air flow to nearly 50,000 L/s – provide ventilation. Heat recovery is included on most of the building’s exhaust systems and when the right conditions exist the system takes advantage of free cooling modes.

There are three modes for getting air into the occupied spaces. First, a series of “eyeball” diffusers located below the clerestory windows in the departures hall jet small volumes of air at a high velocity causin
g air movement with a minimal use of fans.

Second, displacement ventilation in the baggage claims hall pushes air through five large round grills atop each of the three baggage carousels, causing a fountain effect of air that gradually drifts down to the floor. This fountain of air treats only the vertical volume where people are present, leaving the air in the remaining three-story high space alone. To prevent the air near the ceiling from overheating, invisible return air gaps are incorporated in the skylight housings.

The third critical area is the passenger hold rooms. These areas incorporate both a continuous band of jet diffusers and a series of stainless steel “totems.” In heating season, the totem’s lower back side registers are opened to wash the curtain wall with warm air, preventing possible condensation (see photo p. 27). In cooling mode, the upper register is used to push cool air high into the hold room where it will begin to gently drift down on passengers, minimizing drafts.

Controls and enhanced air filters

The overall building is controlled by a series of distributed computers that measure ambient conditions, outside conditions, and the status and performance of equipment. Fans speed up or slow down based on heating, ventilation and air-conditioning requirements. Carbon dioxide and volatile organic compound (VOC) sensors throughout the building measure the air quality. Outside air quality is also measured and the two are compared. If the outside air is poor, perhaps due to jet plane exhaust for a certain period of time, the fresh air intake is minimized.

Rather than using traditional fine-mesh filters, the building has coarser mesh filters with electrostatic enhancement. This technology has an electrostatic filtration system on a very slim filter that uses electricity to capture the very fine contaminants. The end result is an air filter only twice the width of a traditional home furnace filter that achieves a very high efficiency (85%+).

Airports use a lot of water, for washrooms, kitchens and maintenance. Besides low-flow equipment, the building has end-of-line instantaneous water heaters which generate hot water only when it is required.

Lighting that enhances

the architecture

With the abundance of natural light streaming into the building, the challenge for the lighting design was how to emphasize the stunning architectural features. Upon entering the terminal building, for example, travelers are greeted with an abundance of natural wood, including a curvilinear wood ceiling that has been interpreted as waving fields of wheat. The artificial lighting used here had to exude a sense of warmth.

During four long nights of installation, electrical designers worked in the departures hall adjusting the numerous metal halide lights to eliminate shadows and reduce glare. The result is a uniformly “uplit” golden-toned ceiling. The expanse of open area is bathed by “downlights” tucked into the black separation bands of the ceiling.

Another creative use of light is in the passenger hold rooms. Fixtures used to light adjoining retail areas are strategically positioned to reflect light off the dropped T-bar ceilings back into the passenger waiting areas, helping to create a relaxed environment.

A random constellation of skylights within the baggage and lounge areas are surrounded by indigo-coloured LED rings to simulate a prairie sky.

The public artwork program is brought to life through specialized lighting systems varying from internal LEDs to colour changing lamps, to backlighting.

The exterior of the building is lit using an array of linear LED uplight and downlight fixtures.

On the electrical side …

As with any secure facility with automatically locked doors and controlled access points, it is vital these areas be interconnected with the fire alarm system for safe and rapid evacuation if required.

Being a complex, multi-tenanted, common use facility means the IT systems are extremely complex and important to the building’s day-to-day operations. In all, there are over 3.5 kilometres of cable trays within the building, supporting many thousands of cables. There are two large-scale data rooms that house all of the main components required to run a modern air terminal building including airport operations and coordination, signage, PA systems, check-in counters, baggage handling control, and flight information display systems.

Resiliency and reliability are key characteristics of a modern airport, which means ensuring power is maintained during an emergency.

The new building incorporates two-2000 kW diesel generators, each capable of operating for 24 hours from large fuel storage tanks. After power is restored, the generators automatically synchronize with the utility power system to seamlessly transfer power from generator power to utility power, without even so much as a dip in the lights.

At the time of design, this was one of the first airports in North America to have full on-site back up diesel-electric generation.

While most buildings have only a single source of power from Manitoba Hydro, this one has two. Electric power is provided to the airport property at 24,000 volts, and is eventually knocked down to 600 volts in the airport by high capacity transformers.cce

Owner: Winnipeg Airports Authority

Architects: Stantec (prime); Pelli Clarke Pelli (master)

Mechanical & electrical prime consultants: SMS Engineering (Garry Bolton, P.Eng., Russell Lavitt, P.Eng., Chris Hewitt, P.Eng., Ian Kelly, P.Eng.)

Mechanical sub-consultants: Stantec (Blair McCarry, P.Eng., Robert Abbenhuis); Smith + Andersen (Doug Smith, P.Eng., Kevin Sharples, P.Eng.); The Mitchell Partnership (John Lowden, P.Eng.)

Electrical sub-consultant: Mulvey + Banani (Bob Lymer, P.Eng.)

Structural consultants: Crosier Kilgour (prime); Halcrow-Yolles

General contractor, terminal building: EllisDon

Program management: Parsons/Wardrop (Tetratech)


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