U of T researchers aim to increase energy efficiency of aging Toronto apartment towers

Thursday, May 12, 2011 10:34:00 AM

Research News

Researchers in the Department of Civil Engineering are working on a plan to increase the efficiency of aging apartment buildings in Toronto by creating an outer perimeter whose temperature varies between the inside and outside temperature.

Nested Thermal Envelope Design, or NTED, is essentially a "building within a building" and is designed to control air flow, heat flow and moisture transfer.  Developed by U of T Civil Engineering Professor Kim Pressnail, Ryerson University Professor Russell Richman (Architectural Science), and U of T Civil Engineering Ph.D. candidate Marianne Touchie, it allows the temperature of a perimeter to drift between the core and exterior temperature, using a heat pump between the perimeter and core space. "Not only are heat losses moving from the core to that exterior captured in that perimeter zone, we're also able to take advantage of passive solar gains from the exterior," Touchie said. "By transferring that heat by an interior heat pump, we can use those losses and that potential solar gain to heat the core space."

Studies have shown energy savings in a single family home of 74 per cent using NTED.  In an apartment building, the team is aiming to increase that percentage.  Using NTED, the perimeter would be created using the balconies. Air tightness may also be a problem, but the amount of ventilation to each unit can be varied using a dedicated outdoor air system, or DOAS, which can have 83 per cent energy savings. 

There is also a tendency to increase efficiency in high rise buildings by trying to seal the suites, which in the past were ventilated by increasing the pressure in the corridors.  Energy efficiency may also be increased by installing carbon dioxide sensors, reducing ventilation to unoccupied rooms and increasing ventilation only when people are present.

Dr. Pressnail and Ms. Touchie presented their design at the recent Building Envelope Solutions conference held April 13, 2011 in Toronto. Click here for a brief video of their presentation and for a link to a longer article.

This is an edited excerpt of an article found at

Further information on researchers:
Kim Pressnail: http://www.civil.engineering.utoronto.ca/staff/professors/pressnail.htm
Russell Richman: http://www.ryerson.ca/richman/index.html