Retro Housing Retrofitted for the Modern Age: A Case Study

The Ken Soble Tower project sought to rehabilitate a post-war apartment in Hamilton, Ontario. The building was completely upgraded, inside and out, to achieve Passive House standard, reducing greenhouse gas emissions by an impressive 94 per cent. The success of the Ken Soble Tower retrofit demonstrates a pathway to revitalizing similar aging building stock across North America through ultra-low energy retrofits. Additionally, it serves as an example of the positive impact such projects could have on the built environment and local communities, while improving occupant quality of life, reducing operating expenses, and contributing to overall carbon reduction in urban areas.

The Goal

Built in 1967 at 18 stories and 80,000 square feet, the Ken Soble Tower had been in a state of deterioration for some time as the oldest high-rise multi-residential building in CityHousing Hamilton’s portfolio. The goal was to retrofit the building to achieve EnerPHit certification, a branch of the Passive House (PassivHaus) standard designed specifically for retrofits. The building overhaul would include nearly every facet of the building from the building envelope, mechanical systems, electrical, plumbing, and safety systems to interior upgrades to its 146 units to support aging in place, accessibility, comfort, and overall improvement of the occupant experience. As public housing, cost was a key consideration, and the team set out to complete the retrofit at a fraction of the cost of a new build.

The Challenge

The current building had significant challenges including a deteriorating envelope, lack of insulation, inadequate ventilation, and lack of thermal controls. While ERA Architects was originally going to re-clad the building with an entire wall assembly outside the existing brick, a visit to the ROCKWOOL booth at the Construct Canada exhibition changed everything.

The Solution

After introducing the architect to the DuROCK PUCCS NC EIFS system incorporating ROCKWOOL stone wool insulation, the entire plan for the building envelope was revised. The resulting cladding design includes a six-inch thick stone wool EIFS system. ERA Architects liked three main things about the system: first, and most obviously, the non-combustibility (important given the vulnerability of the senior-aged occupants); second, the excellent moisture control offered by the stone wool and the unique, built-in drainage layer cut into the back side of the insulation; and third, the liquid applied water resistive barrier (LAWRB). In all, 50,000 square feet of ROCKWOOL stone wool insulation was incorporated into the new façade, helping to realize the R-38 effective R-value required to achieve EnerPHIT certification. The EIFS system fi t the need for cost effectiveness (the system helped reduce labour costs), ease of install, high-quality composition, a favourable sustainability profile as well the top-notch technical support, provided by ROCKWOOL and DuROCK. The upgraded building envelope with inorganic stone wool will also help contribute to better air quality, since mold was previously an issue. Additionally, it created a more resilient building, able to stand up to harsher conditions as a result of climate change in the region, effectively future proofing the building and better protecting its senior residents. In fact, thanks in part to its tight and super insulated building envelope, ERA Architects notes that Ken Soble Tower, “demonstrates passive resilience to extreme conditions: In case of failure of active systems, the building will stay warm in winter for up to two days (compared to two hours in a typical building) and below dangerous heat levels in summer for up to four days (compared to half a day in a typical building).”

Overall, Ken Soble Tower will now provide residents with improved comfort and control of their indoor environments while substantially reducing energy demand. At its peak, the total energy needed to heat or cool each unit will be equal to the energy needed to run three incandescent light bulbs (100W). The retrofit now positions Ken Soble Tower as a true asset as well as a proud and prominent landmark in Hamilton’s waterfront – fitting, as it now stands as one of the world’s largest EnerPHit certified projects.


Architect: ERA Architects

Contractor: PCL Construction

Passive House Consultant: JMV Consulting

Location: 500 MacNabb St. – Hamilton, ON

Year: Spring 2021

Project Size: 18 stories, 146 units, > 80,000 square feet

ROCKWOOL Product & Application: 6” ROCKWOOL Stone wool insulation – 50,000 square feet of 6x24x48” as part of the DuROCK PUCCS NC Exterior Insulated Finish System (EIFS)

Editor’s Note: This case study is reprinted with permission from ROCKWOOL. You can read more case studies online at

Retro Housing Retrofitted for the Modern Age: A Case Study

About DuROCK

For more than 40 years, DuROCK, a Canadian family-owned business, has been a leading manufacturer of top-quality products in the field of Exterior Insulation Finish Systems (EIFS), and Specialty Coatings for floors and walls. The company’s broad range of products and wall systems are subjected to extensive research and rigorous testing to ensure that they meet Canadian Building Code requirements. The company’s new, state-of-the art facility in Woodbridge, the largest of its kind in the industry, has a busy research and development department which develops innovative new products that keep DuROCK on the cutting edge of technology. Learn more about DuROCK at and learn more about PUCCS here

Retro Housing Retrofitted for the Modern Age: A Case Study


The ROCKWOOL Group is the world’s leading manufacturer of stone wool insulation. They offer a full range of high-performing and sustainable insulation products for the construction industry. Their insulation products are based on innovative stone wool technology and today they are the world’s leading manufacturer of stone wool insulation. The ROCKWOOL group also includes a range of sister companies delivering specialist solutions for the horticultural, marine, and offshore sectors.