In 1999, executives at Cadillac Fairview, owners of Canada's largest office complex, the Toronto Dominion Centre (TD Centre), were facing a dilemma: what could be done to make the Centre more attractive to new tenants and even more appealing to its 20,000 current occupants? Already one of the most recognizable landmarks in Toronto's downtown financial district, the development consists of six "Class A" towers totaling 4.5 million sq ft on 5.5 acres. In addition to the above-ground area, the complex features a retail section with 70 stores and two food courts located at the hub of Toronto's 11-kilometer network of underground shopping concourses.

Mr. Rob Furlan, director of property operations at TD Centre, had some big ideas in mind, but he knew that a project of this scope would be an enormous challenge. First, since the office complex houses some of the most prestigious and influential businesses in Toronto, renovation would have to be as unobtrusive as possible. Overnight, each floor would need to be retrofitted and the tenant space made fully operational for the next morning. Second, the buildings are enormous, with the tallest tower at 54 stories, making any renovation project a massive undertaking.

"One of our top priorities was making sure there would be no disruptions during the business day," said Furlan. "The renovation would benefit our clients greatly, but we didn't want them to sacrifice their concentration and productivity in the process."

Knowing what challenges were ahead of them, Furlan and his team developed a plan to make everyone breathe a little easier. They would modernize the complex, making special improvements to many of the lighting, electrical, and mechanical components. A large part of this project included improvements to indoor air quality (IAQ) through hvac equipment and control system upgrades. These enhancements also improved tenant comfort, conserved energy, and minimized environmental impacts on the community.

The Toronto Dominion Centre is undergoing a complete modernization, which included making special improvements to many of the lighting, electrical, mechanical components, and IAQ through hvac equipment and control system upgrades.

The Need To Update

To stay competitive in the market, Cadillac Fairview executives knew that modernization was a key factor in the renovation. In the late 1960s, popular architect Ludwig Mies van der Rohe designed the first and largest building, the Toronto Dominion Bank Tower, which became the anchor for later development. The Centre was well ahead of its time, a gleaming monument of functional beauty and elegance.

Thirty years later, the buildings still exhibit the same aesthetic appeal, but much has changed in terms of building functionality. Rightfully so, the last few decades have seen more interest in the health, comfort, and productivity of office employees. Advanced tests measure the levels of airborne contaminants such as carbon monoxide, carbon dioxide, lead, asbestos, radon, and other environmental hazards often found in older buildings. Studies show that poor IAQ affects workers in many different ways, making them less alert and therefore decreasing productivity. Specific medical conditions known as Sick Building Syndrome (SBS) and Building-Related Illness (BRI) have surfaced into costly and high profile lawsuits. The Occupational Safety and Health Administration (OSHA) and ASHRAE have released strict guidelines with which landlords and office developers must comply.

The planned modernization was a step in the right direction, but the team decided to go even further and join Toronto's Better Building Partnership, an initiative that urges building owners in the city to improve energy efficiency, renew aging building systems, and reduce greenhouse gas emissions. The goals of the innovative public-private partnership include a 20% reduction of carbon dioxide emissions, the creation of new jobs, and a renewed interest in the city's downtown area. The executives at the TD Centre knew they could not complete a project this large by themselves. They needed experienced consultants to help them bring their visions of a new and improved Centre to life.

Meeting The Challenge

Enter Ed Golfetto, a senior project manager for DukeSolutions, the retail arm of Duke Energy and one of the fastest growing energy services companies in North America.

"The real challenge was the sheer size of the project," said Golfetto. "We had to make sure that each piece of equipment installed or retrofitted worked properly and we had to do it one floor at a time."

For months, Golfetto worked with lead design engineers Kaya Corabatir, P.E., Harold Murray, P.E., and William Todorov, P.E. to plan the future of each of the six towers, named appropriately Tower 1, 2, 3, 4, 5, and 6 - from oldest to newest.

Change Is In The Air: Towers 1, 2, and 3

What the Centre, specifically the three oldest towers, needed was a total refurbishment that included a simultaneous retrofit of all of the existing flush-mounted lighting fixtures and the hvac control systems. To some, these two projects would seem mutually exclusive, but the secret lies in the fixtures themselves. Small diffuser slots hidden within the lighting fixtures distribute air into the office space. By the end of the renovation, more than 100,000 of these multipurpose fixtures will have been retrofitted and refurbished. The purpose of the retrofit is threefold: to replace the old with the new, save energy and improve the IAQ and environment for the tenants.

One part of the project involved the conversion of air-handling systems. Previously, Towers 1 and 2 were ventilated and air conditioned by central air-handling units located on the two lower-level mechanical floors in the buildings. These systems delivered constant volumes of cooled air that then were reheated by steam coils to match the floor cooling load. Using pneumatic valves to regulate the steam quantity, the space temperature was determined by only two reheat coils per floor, resulting in a limited amount of interior temperature flexibility for the occupants.

To solve this problem, the team removed the 30-year-old constant volume boxes in Towers 1 and 2, and installed variable-air valve (vav) systems in their place (Tower 3 was built with vav systems). In total, there would be 3,500 new vav controllers and nearly 25,000 digital control points, eliminating the need for reheat and giving tenants more flexible temperature control. There are now approximately 30 temperature control zones per floor. There were two total for each tower before the project started.

Another advantage to installing the vav systems is that, in addition to added comfort for the tenants, the landlord now has advanced temperature-reporting capabilities. Existing front-end software was upgraded to allow the building operator to find the hot and cold spots in the towers from a personal computer. "The vav systems allow for a new level of troubleshooting," said Golfetto. "A building operator can now get an instant picture of what is happening in the heating and cooling systems on each floor and head off any problems before they become complaints."

To control the quantity of air, all of the supply and common return fans were retrofitted with variable-frequency drives (vfd's). Velocity sensors were mounted to track air volume and maintain building pressurization, ultimately saving fan energy and minimizing drafts in winter months. Supply fan motors were replaced with smaller, more efficient models, to take advantage of the reduced cooling load.

Air quality in the towers was, of course, also a primary consideration. Carbon dioxide (CO2) sensors that compare gas concentrations inside and outside are being added to a minimum of four locations per building. These monitors will calculate the ventilation rate and ensure that a minimum supply of 25 cfm of outdoor air per person is being pumped into the towers at all times for the safety and comfort of the occupants. An extra precaution, this supply level is much higher than the ASHRAE 62-1989 requirement of 15 cfm of air.

"We are constantly thinking about why and how we are here making these improvements," said Golfetto. "Sure, we want to save as much energy as we can for our client, but that really comes second to making sure that the people in this building are going to be comfortable, healthy, and productive. Even a 1% improvement in productivity has far greater financial benefit for tenants than the energy savings - that's where the value is."

The Outer Limits

In Towers 1 and 2, there have been similar improvements to the perimeter zones that will reduce fan energy and increase comfort. Approximately 2,300 perimeter induction unit controllers are being installed, while at the same time, converting more than 7,700 of the perimeter induction units' pneumatic valve heads to direct digital control (ddc) for greater control flexibility and occupant comfort. The team added velocity sensors for fan tracking and cleaned perimeter induction unit coils and lint filters to reduce pressure drop. As a direct result of the reduced airflow and cleaner units, the noise levels in the smaller perimeter offices have decreased.

Vfd's were also added to all of the perimeter fans in order to take advantage of the reduced airflow requirements during mild weather conditions and cloudy days.

Makeup Air Unit Modifications: Towers 5 and 6

Towers 5 and 6 received upgrades similar to those in the older towers, with a few exceptions. As the newest buildings in the Centre, they were already equipped with vav systems during construction. New motors and vfd's were added to the existing supply and return fans, and CO2 sensors were likewise installed.

The biggest impact of these changes is improved temperature and humidity control. The air preheat temperature was changed to 40°F to provide free cooling to the air handlers in the winter. The cooling coils in the makeup air unit in Tower 6 were replaced to comply with the ASHRAE 62-1989 requirements for sloped, non-corrosive drain pans. New, gas-fired steam humidifiers replaced spray-type humidifiers that could harbor stagnant water, bacteria, and mold. The new equipment decreases the risk of sickness caused by airborne contaminants, while eliminating the need for environmentally unfriendly chemicals and conserving energy at the same time.

A Chilling Problem: Tower 5

Since Tower 5 was built much later than Towers 1, 2, and 3, its architects incorporated a number of modern components during construction. A few minor improvements were made during the renovation, such as solving the problem of unequal chiller loading. DukeSolutions engineers converted the secondary chilled water loop to variable flow to reduce the pump energy required. They also installed bypass loop and flow measuring sensors to match the amount of primary flow.

"This project has truly been a team effort," said Golfetto. "For the past year-and-a-half, our engineers have been working around the clock - planning during the day, tearing down entire floors at night, rebuilding them by morning. It's amazing to see it all come together like that."

Total Savings

DukeSolutions predicts that by the time this project is over, the Centre will save approximately 21 million kWh in electricity annually - enough energy to power 6,000 homes. Environmentally, they plan to save around 35,000 tons in CO2 emissions.

Later this year, the renovation will be complete, and the DukeSolutions' crew will have moved on to their next project. However, the improvements from this project will last for years to come. Superior lighting quality, enhanced air quality and improved comfort will be the legacy that tenants of TD Centre will enjoy from this comprehensive revitalization. But it is the tenants' increased productivity and effectiveness that DukeSolutions and the executives at the Toronto Dominion Centre regard as their success. ES