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Achieving optimal Airtightness for Deep Retrofit

67 Richmond St. West

Modern City


In its latest commercial retrofit at 67 Richmond St. West, the energy and sustainability team at Dream Unlimited explored ways to improve the energy and GHG performance of this historic building.


The focus was on maximizing the airtightness of the building envelope and internal penetrations to effectively size the new mechanical equipment for this historic property.


If left unattended, envelope leakage would necessitate larger mechanical systems and higher capital costs, while creating energy waste and increased GHG emissions, negatively impacting the building's operating expenses.

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Scope of Work

The entire building was sealed using Aerobarrier technology, a pressurized spray system designed to seal holes as large as 5/8” and as fine as a human hair follicle.

Each floor was compartmentalized and sealed individually to ensure optimal airtightness around each of the openings and penetrations, as well as window and wall assemblies.

Whole building airtightness testing was conducted by Building Knowledge Canada.

Mechanical design and energy modeling were performed by HAMMERSCHLAG & JOFFE INC., Consulting Engineers.


  • The building achieved a 77.4% reduction in air leakage.

  • Energy modeling indicates that the pre-sealing leakage showed a “Normalized Leakage Rate (NLR) of 2.6 L/s per m² of building enclosure area at 75 Pa.”

  • The value of 2.6 L/s per m² exceeds the Toronto Green Standard default value of 2.0.

  • Given the success of the Aerobarrier application, we conservatively estimate that this test would produce a result today of a maximum value of 1.5 L/s per m².

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Judges’ Comments

“Old historic buildings face extraordinary challenges when it comes to energy and GHG performance. Building conditions such as lack of airtightness can have a significant impact on capital, operational, and environmental performance. Dream’s commitment to tackling these challenges head-on and using innovative technologies to solve historical challenges is a testament to innovation in energy and carbon reduction.”

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