Can affordable housing high rises serve the needs of low-income people and cut carbon dioxide emissions at the same time — all at a competitive cost? Let’s look at a just-completed public housing retrofit owned by CityHousing Hamilton (CHH), which shows what is possible.
The story starts with the 18-storey Ken Soble Tower on Hamilton’s MacNab Street. This CHH property was built in 1967. By 2010, it needed extensive repairs to its structure as well as all-new heating and electrical systems. CHH explored many options, including ‘demolish and rebuild.’
In the end CHH chose to renovate to the EnerPHit standard1. It was a risk. No other building of this size had been renovated to the EnerPHit standard when CHH made its decision in 2019.
EnerPHit is an evolution of the Passive House standard conceived in 1988 for low-rise buildings2. “Passive” means the building is airtight and has extra insulation, and so needs no furnace. EnerPHit extends these principles to renovating high rises. In both standards the goals are the same: slash energy use and maximize occupant comfort.
The trick is to include energy recovery ventilation. When stale air is exhausted, the energy in it is extracted and transferred to the fresh air being drawn inside. Incoming fresh air and outgoing stale air flows through energy recovery ventilators in separate streams; only the energy content of the stale air is transferred to the fresh air. It works with heated and cooled air.
The result: temperature and humidity are steady and comfortable. There are no drafts. Humidity stays in the optimal range to discourage airborne transmission of infections such as COVID. To earn an EnerPHit rating a building must be tested once the renovation is complete. Here are highlights for CHH’s tower:
- Airtightness was 50% better than the target: energy use dropped 89% and carbon dioxide emissions dropped by 94%
- All the structure problems, including asbestos and black mold, were eliminated
- All public spaces were brought up to current accessibility standards and 20% of the suites were brought up to barrier-free standards
- Maintenance and energy cost savings keep housing affordable. Residents will be paying no more than 30% of their income for their home. The building-wide upgrades for accessibility and upgrading 20% of the suites to support barrier-free requirements mean the low-income seniors living in the building will have the option to age in place.
All this is pretty extraordinary when you consider that CHH had no experience with EnerPHit. Nor did anyone else, as this was the largest first EnerPHit renovation in the world at the time. To get these extraordinary results CHH used an Integrated Design Process3. They consulted multiple experts on every key decision during the pre-design and design phase. This helped the team to cope when structural surprises were discovered after construction began in 2019. All the work was finished by late 2021 despite slowdowns due to COVID.
PCL, the general contractor, and Entuituve, the building envelope engineer, also credit regular testing throughout construction for the final performance. It helped building trades adjust to the different techniques required to achieve the EnerPHit standards.
The $34 million renovation is said to be less than the cost to demolish and rebuild a new tower to the same performance standard.
The incremental time and materials to achieve EnerPHit added just seven percent to the total budget. And much of this premium was tied to the business risks of such an unprecedented project. The feeling seems to be that more projects will decrease the perception of risk. This should help to decrease the cost.
Given these exceptional results, why would any approach besides EnerPHit be used to refresh public housing highrises? The Ken Soble experience also suggests possibilities for the thousands of privately owned high rises that were built around the same time. They too are aging and need upgrades.
For more on this interesting project, read at CMHC: Ken Soble Tower Renewal, CityHousing Hamilton retrofits derelict high-rise into seniors housing
at Canadian Architect: Raising the Bar, Ken Soble Tower, Hamilton, Ontario
and at PCL: Ken Soble Tower Achieves EnerPHit Certification
Footnotes
- Read more about EnerPHit at the Passive House Institute: EnerPHit Certification
- Passive House (a.k.a. passivhaus) standards are available here.
- Read more about integrated design processes at NJ Green Building Manual: What is an Integrated Design Process?
