Habitat 67

Outside the box: Iconic heritage building, Habitat 67, necessitates creative restoration solutions

Perched on the banks of Montreal’s riverfront, Habitat 67 is a historical landmark, a building commissioned as part of Canada’s Expo 67 centennial celebrations.  When designed, and built by architect Moshe Safdie, Montreal’s Habitat 67 landed outside the box of traditional architecture with its concrete, modular pod construction, stacked in unusual and irregular configurations.  Over the years, it has drawn sightseers and architectural enthusiasts from across the globe to study its unique composition.  Habitat, through its design, was meant to introduce a forward-thinking housing option—a hybrid between the single-detached home and urban multi-unit apartment building. It endeavored to provide families with a greater sense of community in higher density dwellings, with gardens, green space, sunlight, terraces, walkways and private streetscapes.

Balancing Preservation and Performance

When Moshe Safdie decided to undertake a major restoration of his own unit within the Habitat complex, his vision aimed to safeguard the past, while simultaneously making profound improvements to the building envelope. Specifically, the goal to increase its energy efficiency while respecting the building’s heritage designation proved a challenge as unique as Habitat itself--one that necessitated an equally inventive, outside-the-box approach.

The Challenge

Architect Ghislain Bélanger of the Montreal firm CO12 Architecture worked closely with Safdie’s team on the design and restoration process. From an energy perspective, the team came up against an array of difficult parameters:

The retrofit could not change the looks of the interior or exterior of the unit.

• The building’s unusual wall assembly left little space for insulation.
• Raised floors serving as “plenums” for ducts and electricity also posed challenges for insulation and air/vapor tightness.
• A desire to use non-combustible insulation was expressed.
• The insulation had to be removable, so changes could easily be made, if necessary, in future. 
• The unlevel concrete wall surfaces further limited some options. 
• The insulation solution needed to address both durability and preservation. Moisture and air management were important factors to combat potential issues moving forward.

The Solution

Weighing their options, the architectural team selected stone wool insulation as a non-combustible solution that could effectively address the building’s challenges, while improving efficiency, durability, air quality and air/moisture management. The technical issues proved considerable, and the team turned to ROCKWOOL’s Building Science team (RBS) to help. The RBS team modelled and tested a number different assemblies. The idea of using the company’s COMFORTBOARD product inboard of the building’s exterior walls at first seemed a reasonable option. However, the team could not resolve the issues surrounding the unevenness of the concrete walls. Normally, one would simply increase the wall thickness in order to square off and create a more level surface, but given the historic designation and inability to modify the interior, a more unconventional approach was applied. 

A z-girt system would compensate for any irregularities of the wall surface, while CAVITYROCK® would improve thermal performance and work in tandem with other details to resolve air/moisture concerns. Modelling proved it to be a suitable remedy. However, the team were under no illusions that it was the perfect thermal solution. However, it would meet other strict parameters and prevent the most pervasive threat that could jeopardize Habitat’s durability--moisture.  

Ultimately, the team designed an assembly whose components would work in tandem to control air flow and vapor drive and increase drying potential.  To prevent any moisture-related issues and better preserve the building envelope, the following wall assembly was employed: 

1)      The existing concrete walls were stripped back and cleaned—removing some damaged wood and the old polystyrene insulation.

2)     31 mm liquid air and water barrier was applied.  The product stops water and air penetration, but does not impair the movement of vapor.

3)     A z-girt system was installed against the wall and ROCKWOOL CAVITYROCK® insulation was added.

4)     Smart vapor retarder was installed to allow the wall to dry either toward the inside or the outside depending on the direction of the water vapor flow (directed by temperature and/or water vapor pressures). 

In the end, the creative approach to the retrofit should help Habitat endure for years to come, while simultaneously improving comfort, energy efficiency, safety and durability. Residents will benefit from more stable and homogenous indoor temperatures, passive fire protection due to the buildings non-combustible stone wool insulation, and better indoor air quality as a result of CAVITYROCK’s mold and moisture-resistant qualities.  Moving forward, the preservation and improvements on Moshe Safdie’s unit can serve as a model for similar, future retrofits.