Greening existing buildings need not be painful, say experts

Some leading authorities on improving the sustainability of existing office buildings emphasized at a recent event in Ottawa that the most effective actions are sometimes the simplest ones.

The Canada Green Building Council held a workshop on Friday that brought together experts to share their knowledge and experience on the topic of greening existing buildings.

Shawn Carr, a project manager for consulting firm Halsall Associates in Ottawa, pointed out the challenge owners and managers of existing buildings face in making their facilities greener. He said the average office building in Canada uses about 29 to 35 equivalent kilowatt-hours per square foot, while newer high performance buildings are generally designed to use half of that.

But there are savings to be had with existing buildings, he said, and it doesn’t always require big renovations or new equipment.

“You can have a building that has older systems in it,” he said. “That doesn’t necessarily make it a bad building from an energy perspective. How the building is operated and what people are doing inside the building can have a much bigger impact on your overall performance.”


Carr and others touted the value of “retro-commissioning” as a way to achieve significant efficiencies.

“The primary objective of retro-commissioning is to optimize the performance of your existing systems and your building’s operations and maintenance procedures,” he said.

He cited a U.S. study of about 640 buildings in which retro-commissioning helped achieve average energy savings of 16 per cent, and the money that was spent on improvements was generally made back within a little more than a year.

Tenant engagement

Carr also talked about the importance of working with tenants to achieve energy efficiencies because as much as half of the energy used in office buildings is from tenant activity.

Yvon Morin, a manager of technical services with Bentall Kennedy and responsible for Ottawa’s World Exchange Plaza, agreed with the importance of tenant engagement as a way to make buildings run greener.

He talked about how his building used to automatically provide lighting and ventilation throughout much of its office space on Saturdays in case people were there. In an attempt to better manage energy usage, building management consulted with its tenants to see how necessary this was.

“Pretty well all the tenants agreed that we could get rid of the lighting on Saturday and the air ventilation, and just turn it on when they require it,” Morin said. “So all they need to do is make one phone call and the lights and HVAC is started, and we’ve saved quite a bit of money just from that fact.”

While assessing a range of measures to improve the building’s efficiency, Morin said it was the relatively simple measures, such as this, that have been most effective.

“Tenant engagement and retro-commissioning produce the best results,” he said. “Talk to your tenants. You’ll find out that they are interested in doing their part, in helping out and making sure your building is efficient.”

Small steps toward green buildings

Jeff Clark, a manager of operations for Brookfield Office Properties in Ottawa, talked about how he has taken an incremental approach to greening some older buildings. This has included conducting energy audits, replacing equipment where appropriate and using automated systems to best utilize facilities’ energy usage.

“All buildings have different starting points, and you need to plan your way toward whatever your objective might be for green buildings,” he said. “Old buildings can still be really good performers.”

The importance of air

Robin Hutcheson, president of Ottawa-based Arborus Consulting, talked about how many buildings waste energy through over-ventilation.

“Outdoor air is the biggest energy piece. That’s the biggest part of your energy pie,” he said.

Hutcheson said that while there needs to be an adequate intake of fresh air to ensure air quality, “what we find more often than not is that buildings are actually over-ventilated.”

He suggested measures such as maximizing the amount of fresh-air intake at times when most people are in the building, and easing off at times, such as night, when fewer people are there. “Demand control is the best strategy,” he said.

Hutcheson referred to an instance in which a building was bringing in enough outside air to keep carbon dioxide levels consistently less than 500 parts per million, when a range of 600 to 800 is acceptable.

After finding this out and adjusting the ventilation, the building was able to use about 40 per cent less natural gas and around 15 per cent less electricity, he said.

“If you’re going to do nothing else, go right to the outdoor air management,” he said. “You can demonstrate savings very, very early in the (greening) process.”

Industry Events