Retrofit of 1980s townhouse complex

Jennings Place is a townhouse complex located in Surrey, British Columbia, consisting of 15, two-story townhouse buildings (totaling 52 units) and a recreation building. Built in 1989 to meet the standard of the day, and now showing its age, the owners of the complex sought to update some aspects of the building, as a number of its components had reached or were nearing the end of their serviceable life. The retrofit work also provided the ideal opportunity to address the building’s energy performance.

The goal: Improved energy performance & long-term durability

Building envelope improvements were identified as among the most effective and efficient means to improve energy performance, lower energy demand, reduce energy costs, and bolster the building’s long-term durability, while also reducing ongoing repair and maintenance expenses. Beyond the economic case for retrofit, the owners also weighed potential positive impacts on occupant health, safety, and wellbeing. Following a thorough building condition assessment, WSP Canada Inc. building consultants presented a detailed, strategic plan to address existing deficiencies and realize project objectives, while fulfilling scope and budgetary requirements.


The Challenge

Moisture management was a considerable concern, given the construction of the existing wall assembly and the local climate. Surrey, British Columbia experiences a six-month wet season where any given day has a 35 percent chance of precipitation. That probability rises to nearly 60 percent in the peak month of November. Overall, the city experiences significant annual precipitation totaling over 2,500 mm. The wall assembly at Jennings Place was original to the building and over 30 years old, with deterioration noted in the vinyl cladding. It had also been installed with a “concealed barrier” approach—that is, it is not completely sealed on the outer face (as in the case of a face sealed assembly)—and it did not have a cavity, or “rainscreen”, to provide drainage and ventilation which facilitates drying potential behind the cladding. It is recognized that the concealed barrier strategy is no longer adequate for the climate of the region. The current building code requires a drainage cavity behind the cladding to prevent moisture accumulation and mold potential. As such, WSP recommended full wall rehabilitation with the implementation of a rainscreen drained cavity wall assembly approach.

Thermal issues were reported, specifically poor thermal performance of the existing wall and window assemblies, resulting in excessive heating costs. Insulation R-values met building code at the time of construction but, with code advancements, were now below levels required by the current code. Improving the building envelope with a higher performing wall system to reduce air leakage and significant heat loss/gains was key to lowering ongoing operational costs. The insulation strategy was a primary focus.

Wall Assembly - Original Construction:

  • Horizontal vinyl siding
  • Building paper
  • 3/8" OSB sheathing
  • Batt Insulation and 2 × 4 wood studs (16" on center)
  • Vapor retarder (4mil polyethylene sheet)
  • 1/2" Interior drywall

Additional deficiencies in the assembly would also need to be addressed to improve thermal performance. Existing windows were double-glazed in non-thermally-broken metal frames. These windows offered very little thermal resistance and were a significant source of heat loss. This type of window is also susceptible to condensation during the colder months of the year, leading to potential for moisture and possible mold/mildew growth. Doors on the outside of the units were not exterior grade, and each unit’s garage door was uninsulated, as were the exterior walls of the semi-conditioned garages. The radiant floor systems were also identified as inefficient, and a more effective solution was sought.


The Solution

The building envelope was upgraded, and a number of building components were replaced. A key strategy to improving thermal and moisture performance of the exterior wall system in each of the complex’s buildings was the installation of a 2” layer of ROCKWOOL Comfortboard® 80 continuous exterior insulation outboard of the sheathing to create a continuous thermal break and reduce thermal bridging. This will serve to increase the thermal performance of the wall assembly, bringing it in line with current BC Building Code. The team also took into account BC Energy Step Code by integrating some Passive House principles with the aim to apply best practices while also future-proofing the building. A more efficient building envelope will result from the addition of the stone wool continuous insulation since thermal bridging can reduce thermal performance by up by as much as 30 – 50 per cent.

Insulating the exterior will also contribute to effective moisture management. The Comfortboard® 80 exterior insulation will help keep the temperature of the sheathing above the dew point, which will reduce the chance of condensation and excess moisture in the wall system. Creating a rainscreen system with stone wool also provides a number of benefits. Not only does it provide a drainage cavity for moisture egress and better ventilation, the vapor permeability of stone wool results in high drying potential, allowing any moisture to easily dry to the exterior. Additionally, it will prevent moisture, mold, and air quality issues, ultimately creating more durable and resilient buildings at the Jennings Place complex. With climate change bringing increased moisture and more severe weather, the complex will now be well positioned to withstand the elements for years to come.

The composition of the exterior and interior stone wool insulation also improves upon each building’s fire resistance since all ROCKWOOL insulation products are made from stone and are noncombustible building materials. Residents benefit from greater fire protection, as stone wool can help to prevent flame spread in the event of a fire and potentially provide extra time for residents to get to safety.

With the completion of the retrofit, one of the most obvious improvements occupants of Jennings Place will notice is an increase in comfort within their suites. The introduction of double-glazed high-performance vinyl windows as well as a vapor permeable water resistive barrier, which was taped and sealed as an air barrier then covered with a layer of ROCKWOOL Comfortboard® 80 continuous exterior insulation, will remedy the drafty environments that were problematic pre-retrofit, leading to more stable indoor temperatures and a reduction in overall energy demand. The suites will also prove quieter and more resistant to exterior-to-interior noise transfer. A reduction in excessive noise from the exterior has been demonstrated to contribute to improved occupant wellbeing in several ways—from better sleep and less stress to greater productivity and health.

Upgraded Wall Assembly:

  • Fiber cement siding
  • 1 × 4 Pressure-treated vertical strapping (16" on center)
  • 2” ROCKWOOL Comfortboard® 80 Continuous Exterior Insulation
  • Water-resistive barrier, sealed as the primary air barrier
  • 1/2” Borate-treated plywood sheathing
  • Batt Insulation and 2×4 wood studs (16" on center)
  • Vapor retarder (4 mil or 6 mil polyethylene sheet)
  • 1/2” Interior drywall

In selecting an exterior insulation strategy, WSP’s building consultants aimed to reduce the construction impact on the existing structure, especially within the interior, maintaining wall thickness on the inside and reducing disruption to the tenanted units. Insulating primarily from the exterior with ROCKWOOL Comfortboard® 80 stone wool rigid board insulation also made sense since cladding replacement was part of the overall scope of work. The goal was to improve energy performance as much as possible within budget. The addition of the exterior insulation increased the R-value of the wall system by R-8.

In addition to improving insulation levels, further improvements in energy efficiency were achieved by addressing air tightness, ventilation, and upgrading other parts of the envelope such as windows and doors. Detailing of the air/vapor barrier, particularly around wall penetrations, was meticulous. Ventilation was also improved in kitchens and bathrooms to help control moisture and humidity. Radiant heating was disconnected and replaced with heat pumps. Domestic water distribution piping was replaced in each unit and components like faucets and mixing valves were replaced for greater water efficiency. In addition to passive fire protection measures such as the noncombustible stone wool insulation, life safety enhancements included active measures such as new smoke and carbon monoxide alarms, as well as fire extinguishers. Minor repairs were made to the envelope, where necessary, including to the existing polyethylene sheet and framing members. Upgrades were also made, where possible. Anywhere the vapour retarder was found to be compromised and unrepairable or non-continuous, a 6 mil polyethylene sheeting was installed in place of the original 4 mil product. Additionally, any original fiberglass insulation batts that were found to be slumped or damaged by mold or moisture were replaced with high-performance ROCKWOOL Comfortbatt® stone wool insulation. In keeping with the retrofit project’s sustainability profile and tight budget, selective replacement reduced waste to landfill and helped reduce costing.

Overall, the energy retrofit of Jennings Place is anticipated to result in significant savings from the energy conservation measures (ECMs) and envelope improvements, shaving at least $50,000 per year from operating and repair costs while bolstering efficiency, building durability, as well as occupant safety and comfort.

The success of this retrofit project is largely attributed to its holistic strategy, keen attention to detail, ongoing oversight and collaboration between WSP and the general contractor (RJS Construction), as well as specifying the right building components. A collaborative and integrated approach by all members of the build team is expected to become the gold standard in renovation, retrofit and new construction. This is especially true as the built environment moves towards higher codes, standards, and performance (e.g. net zero and Passive House) and as a holistic approach to high-performance building becomes the accepted norm. Ultimately, owners, communities, residents, and the environment stand to benefit from a collective commitment to building better.

Jennings Place

Surrey, British Columbia, Canada

Proper detailing is always critical, especially when it comes to the building envelope. Whether light improvements or those designed for deep energy reductions, a successful retrofit depends on all parties and stakeholders working closely together toward the overall goal. Even then, achieving key goals relies on a holistic strategy and high-performance building materials. We chose ROCKWOOL for this project due to its noncombustibility, vapor permeability and high drying potential, thermal performance, as well as its ability to enhance the occupant experience and the overall durability of the buildings.

Masoud Attar

Building Consultant, WSP Canada Inc.

Project Data


Retrofitted: February 2021 - June 2022
Originally Built: 1989


7775 120A St.
Surrey, BC

Original Architect

ELBE, LOCK, WALLS & Associates Inc.

Architect/Engineer/Building Consultant (2021)

WSP Canada Inc.

Renovation Contractor

RJS Construction Ltd.

Building Type

Residential Townhouse Complex

Building Size

15 two-storey townhouse buildings comprising 52 units
1 recreational building

Retrofit Budget

ROCKWOOL Cavityrock® – Rainscreen Application – 50,000 sq. ft.

ROCKWOOL Product & Application

ROCKWOOL Comfortboard® 80 – Continuous Exterior Insulation
ROCKWOOL Comfortbatt® – Exterior Cavity Walls