How to Renew Our Old Apartment Buildings

Our old apartment buildings can be new again with Passive House design.

Before and during tower renewal
Before and during tower renewal.

 Tower Renewal Partnership

Fifty or 60 years ago, architects and builders didn't worry much about insulation and moisture control; it just caused problems. It was much simpler just to build a brick wall and add a lot of heat to drive moisture out of the walls. Air conditioning didn't enter the picture, although buildings often had cross-ventilation and balconies. This tower (shown above) in Hamilton, Ontario was a good example of the genre; it has a nice, compact plan with lots of corners for ventilation, with the exterior brick still in pretty good shape.

It also had no insulation, inadequate ventilation, mold and hazardous materials, and lousy thermal control. The brick is just sitting on the concrete slab, so the whole thing is a giant thermal bridge, probably radiating and leaking more heat to the exterior than it keeps inside. It's not very comfortable or healthy; in many cities they would demolish it, which is how we lost architectural icons like Robin Hood Gardens in London. But there is a lot of concrete in this building, a lot of embodied carbon that would have to be replaced if a new building was built.

Fortunately, 500 Mcnab didn't get torn down. Instead, it is the new poster child for Tower Renewal, a concept initiated by ERA Architects in 2007 in Toronto, which once had a progressive Mayor and government that was interested in such things. The Tower Renewal Partnership's goals include:

  • Rehabilitate our aging rental housing supply to meet modern standards of comfort, health, and energy performance – while maintaining affordability.
  • Expand opportunities for community-led economic diversification, social infrastructure, and cultural production to enable post-war tower neighborhoods to become more healthy and complete communities
  • Leverage the legacy of postwar tower urbanism toward regional growth, sustainability, and transit connectivity, building more resilient and thriving urban regions.

This building is down the road from Toronto in Hamilton, Ontario, a former working-class steel town that has had its ups and downs, but has a vibrant green building community and a few very interesting Passive House social projects.

Graeme Stewart of ERA and Ya'el Santopinto recently presented the Ken Soble Tower at the Global Passive House Happy Hour, one of the few good things to come out of this pandemic, and graciously shared their slides with Treehugger. (They start at about 12:30 in the video after all the happy talk.)

The building is being renovated to the EnerPHit standard, a version of Passive House adapted for renovations, which requires a bit more flexibility. But that doesn't make it easy.

Base conditions
Base conditions. Tower Renewal Partnership 

Looking at this list, one has to wonder if it's worth it, it seems almost everything inside the building is due for replacement. But it's a lot of concrete, like most buildings of the period, the units are generous, and possibly most importantly, it exists; its hard to get these buildings approved in these NIMBY times.

Passive House Renewal
Passive House Renewal.  Tower Renewal Partnership

The restored units have sprinklers for life safety and a complete wrap of noncombustible insulation in an airtight envelope with triple-glazed windows. The balconies were a nice feature to have, but they were impossible thermal bridges, like radiator fins to the exterior with two edges connecting to the building, but now the residents have air conditioning.

ventilation systems
Ventilation Systems.  Tower Renewal Partnership

Ventilation is one of the most difficult aspects of a building like this. In condominiums, where the units are owned by individuals, there are often individual AC units in each unit, exhaust fans in the bathroom and fresh air admitted under the door to the hall. In rental units, you need a system that is easier to maintain, which is why it is often centralized for easy access. Getting direct ducting into suites like this is the best way to do it, but it certainly isn't the cheapest.

Thermal bridging at windows
Thermal bridging at windows. Tower Renewal Partnership 

Note the care that is going into the design of every detail to reduce thermal bridging, the conducting of heat from inside to out. You have to think about everything, and it all works together.

Fifty years ago during the energy crisis of the seventies, everyone suddenly became concerned about energy consumption and started wrapping buildings in insulation and vapor barriers. But similar consideration wasn't given to ventilation, and since the walls were no longer leaky, the humidity levels inside the units shot up. Thermal bridges weren't considered, just the R-value of the insulation, so there would be cold spots with condensation all over the place, in corners and near floor and ceiling connections, all becoming thriving mold farms. I remember seeing walls in apartments with vertical lines of mold where the steel studs were.

Since then we have learned (mostly thanks to the research done in the Passive House world) that good thermal design is a careful dance of insulation to keep the heat in, ventilation to keep the moisture levels under control, and elimination of thermal bridges so that the interior surfaces are all an even temperature, and consistently too warm for condensation to form.

air tightness test
Blower door test.  Tower Renewal Partnership

The other thing we have learned is you have to test and verify that the building is built to the specifications and meets the criteria. I like the way that the Tower Renewal Partnership has an "Air Boss" monitoring every step of the job. Finding leaks after the fact is never as easy as doing it right in the first place and catching mistakes early.

The lessons of London's Grenfell fire disaster are clear here as well: no late substitutions to save money (in Passive House it would be back to the drawing board) no chimney-like gaps where firestopping was not properly installed, no combustible or off-gassing materials, no cheaping out.

90 percent reduction in greenhouse gases
 Tower Renewal Partnership

There are many things to love about Passive House; as they note on the Accelerator website, "Passive House design and construction creates comfortable, healthy, energy-efficient, resilient, and beautiful buildings."

The Ken Soble building also shows how it can give new life to existing buildings, provide greater accessibility, life safety, and community. This is how it's done.