Renewing the Building Envelope: A Multi-residential case study

All photos courtesy GRG Building Consultants Inc.
All photos courtesy GRG Building Consultants Inc.

By Brian G. Shedden, BSSO and Gerald Genge, P.Eng., C.Eng., BDS, BSSO, C.Arb., Q.
Several years ago, this author was invited by University of Toronto’s Ted Kesik, PhD, to join a technical advisory committee formed to provide a critical eye for work he was undertaking with Ivan Saleff, B.Tech (Arch.Sc.), M.Arch, OAA, MRAIC. The task was to produce a single-source document that would present state-of-the-art information on high-rise tower renewal; specifically Toronto’s aging stock primarily erected during the 1960s and ’70s. The result of Kesik and Saleff’s work was the resource document, Tower Renewal Guidelines.1

While tower renewal seeks to re-invent the ‘tower-in-a-park’ phenomenon that lead to their original construction through re-imagining everything from energy and transit to the economy, this author’s interest lay in a much more pedestrian aspect of the concept: how to maximize the existing building envelope’s performance while optimizing return on investment (ROI) in a fully-occupied building. Taking a concept from a page and bringing it to life is an extraordinary challenge—and this article explains the process of a multi-residential renewal project.

Planning for upgrades
Built in 1972, York Condominium Corporation (YYC) No. 118 is a twin-tower site located in Toronto’s historic Swansea neighborhood. With 16- and 18-storey buildings supporting 332 units, the project comprised:

  • unvented brick masonry on concrete block backup walls;
  • virtually no insulation;
  • large expanses of cast-in-place concrete; and
  • single-glazed windows.

These same features can be found on upward of 2000 similar structures around the Greater Toronto Area (GTA).

The YCC 118 buildings had continuously leaked since they opened. A lawsuit against the developer in the late 1970s secured some funding, but repair after repair had failed to stop the leaks. Of course, over this same period, the masonry and concrete were spalling, sealants had failed, wind whistled in though inadequate windows and doors, and the continual funding of an ever-increasing load of urgent repairs brought the condo board to a point where it was ready to look at alternatives. There are two sure-fire ways to tell when it is time to act: when the water comes in, and when the concrete falls down.

Attention to detail during the building envelope renewal project mockups was critical for project success.
Attention to detail during the building envelope renewal project mockups was critical for project success.

Unlike many of the rental apartment buildings in the same condition and general area, condominiums have a duty to plan for future restoration requirements and ensure they are adequately funded through a reserve fund plan (RFP). In Ontario, under the 1998 Condominium Act, a condo corporation must keep an adequate financial reserve to respond to the building’s requirements for restoration over time. In fact, this fund must look 30 years into the future as many building components last a significant period before requiring repair or replacement. Having adequate monetary resources on hand to accomplish a task that might not occur for more than 15 years requires some careful planning, both engineering and financial.

In 2011, having completed the mandatory three-year cycle for reserve fund updates, GRG Building Consultants was retained to conduct a Class 2 reserve fund study (RFS). Class 1 is done when the condo is first registered and it is the first RFS conducted. After the initial RFS, a Class 2 is conducted every six years, while alternating the three-year period with a Class 3 RFS. Class 2 involves detailed visual investigation of the conditions of common elements throughout a condominium, while Class 3 is essentially a financial update of the previous study, taking current inflation, interest rates, construction, and consumer price indexes into account.

Built in 1972, York Condominium Corporation (YYC) No. 118 are condo towers in Toronto. They were subject to a recent recladding project.
Built in 1972, York Condominium Corporation (YYC) No. 118 are condo towers in Toronto. They were subject to a recent recladding project.

As these buildings were due for a Class 2 RFS, in addition to the normal ‘ground-level’ survey of the building envelope, there were investigations from swing stages to access and assess all areas of the exterior from grade to roof. Essentially, the swing stage inspections revealed the spalling of masonry and concrete was widespread and more severe than previously thought.

Normal remediation practices such as isolated brick replacement or concrete ‘patch and repair’ were no longer viable as the sheer size of the failing envelope components would have rendered the scope of the repairs far beyond what could be construed as routine maintenance. Additionally, repairs or restoration generally involves a ‘resetting of the clock’ where compromised materials or systems are brought back to their original design intent and function. In the case of these buildings, there were problems right from the beginning of construction—40 years of service life meant it was time to see if better options were available.

This photo shows the new parapet cap fl ashing employed on the project.
This photo shows the new parapet cap flashing employed on the project.

The concept of ‘tower renewal’
If we consider the building envelope as the building’s ‘coat’ that covers the bones of the building’s structure, shopping for a new ‘coat’ is a factor of both desired performance and lifecycle cost. A ‘coat’ needs to have many attributes such as style, heat retention, and durability.

The owners wanted energy savings associated with an exterior insulating finish system (EIFS). In this case, the insulation’s thickness was a factor of its aesthetic impact and material cost.

In conjunction with window replacement, EIFS can be cost-effective when looking for a new building envelope for an occupied building. Without disrupting residents and interior living spaces, EIFS allow the existing envelope and structure to stay in service while the coat goes on, and elevates the previous envelope’s performance by harnessing its thermal mass in the service of the new envelope. At the same time, it updates the appearance and reduces energy use and costs.

The existing wall assembly did not have a purpose designed vapour barrier, and once the concept of overcladding with EIFS and the window and door replacement was understood on a conceptual level by the condo board, the rationalization of the potential costs and benefits versus undertaking a major repair project was fed into the RFS. When looking at the lifecycle costs of options, some of the major considerations include:

  • What is the anticipated cost of repairing the existing?
  • How long will the repair last?
  • What will be the future cost of carrying out the repairs again (and again)?
  • What is the anticipated cost of an overcladding project?
  • How long will the overcladding last before requiring repairs?
  • What are the future costs of the overcladding?
  • What are the energy costs today versus future energy costs if the repair strategy is undertaken?
  • What is the impact on energy costs now and into the future with the overcladding option?

Once the concrete and masonry is overclad, it is no longer exposed to the elements. Within a properly designed overcladding, they are now contained inside the warm area of the wall system; they essentially remain encapsulated and stable in their current state indefinitely. In this case, masonry, as well as the concrete was spalling. Cosmetic repairs to the finish coat and periodic sealant repairs are the primary future costs.

Renderings of the new façade for the two residential towers.
Renderings of the new façade for the two residential towers.
The completed east side of the project’s Phase 1.
The completed east side of the project’s Phase 1.

 

 

 

 

 

 

 

 

 

Further considerations
Beyond these questions and answers, the fact remains if a traditional repair is carried out on an aging building, the result is an aging building with repairs. If an overcladding project begins, an aging building can look new and provide thermal performance exceeding many of today’s new buildings. As Kesik once said, “It is like having a 1960s muscle car with the mileage of today’s best cars.”

There is one other aspect that needs to be considered, and it is one without any hard and fast answers, because it is too early in the renewal game to understand its full impact: real estate values. If a 93-m2 (1000-sf) unit in a 40-year-old tower sold for $320,000 before the renewal effort, what will it be worth after the work is complete? This author believes the answer to this question will forever tilt the decision-making process in favour of the renewal option, but time will tell.

Looking around at recent building construction, it seems Canadians have spent an entire generation building all-glass buildings. Despite the decidedly cold climate, the industry has moved from the massively thick masonry walls of a century ago to constructing exterior walls with little more than 25-mm (1-in.) thick insulated glazing (IG) units. Depending on who is asked, and how it is calculated, standard glass-clad construction offers the thermal performance of R-4. The original 40-year-old structure of block, brick, and a thin layer of insulation gave an R-8 before the renewal started—the process is adding another R-12 to the envelope, reaching R-20 nominally. This is five times the thermal performance of the new buildings.

Proceeding with the project
After evaluating the pros and cons, both performance and financial, it became clear the appropriate course of action was to proceed with the tower renewal project including new windows, doors, and a pressure moderated rain-screen EIFS overcladding. This gave rise to two distinct questions: What will it look like? What are the technical challenges associated with cladding these buildings?

These are potential risks, not just for EIFS, but for every material system from masonry to concrete to curtain wall. Detailing the connections in what are fully vented or drained systems requires adhering to a principle acknowledging water is going to get in; therefore it involves establishing a design, constructible in the field, to manage its exit.

At the same time, there is the issue of what the architectural design of the overclad will look like. The project’s ‘emotional aspects’ of colour, texture, look, and feel can either garner support from present or future unit owners, or grind the process to a halt in no time. With two adjacent towers, similar in overall design, but different in their lines and floor plans, the best approach to this critical element of the project was considered.

Digital models of all elevations and likely perspectives of both buildings were created. The next step was the artistic challenge of designing the look and general colour placement. Since this is essentially designing a new building façade, the sky is the limit.

In a condo corporation with 332 units and hundreds of residents, there will be many different ideas. So, in a nod to the building’s history, the neighbourhood, and planned twin high-rises to be constructed directly across the street, two options were developed by the architect to share with building residents at an information meeting. During the meeting, a full presentation was made on the project process and what to expect as a resident living ‘inside’ the new envelope. Residents were asked to vote on their preferred choice of rendering, a process that continued for a week. Once the votes were tallied, a clear consensus had emerged and the detailed drawings for the tender package could commence.

The two residential towers, totalling 332 units, before renewal are shown above and below.
The two residential towers, totalling 332 units, before renewal are shown above and below.

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Moving the restoration forward
While the options were presented to building residents, the process of specifying windows and doors continued. Most of the existing single-glazed, mill-finish aluminum windows were original to construction. In past years, previous boards and property management had permitted residents to change their own windows and doors. This process led to some interesting results in terms of materials, types of windows, and the building façade’s general aesthetic—some were white, aluminum, vinyl, and even wood. Normally, the building envelope and its components, including windows, are common elements in a unit maintained by the condominium rather than on an ad-hoc basis by individual owners.

When seeking a window manufacturer, it was important to find one that had invested time, effort, money, and technology into the process of having products tested by independent laboratories against the building code referenced in the Canadian Standards Association (CSA) A440, Window, Door, and Skylight Installation standards. With climate change resulting in more severe storms, higher winds, and torrential downpours, the decision to go for a high-performing window system was the project’s goal. Windows demonstrating an air leakage rating of A3, a water leakage rating of B7, and wind resistance rating of C5 were required. (These ratings are the highest each category can achieve.) Non-combustible materials were also preferred and low maintenance, aluminum framing with a fluoropolymer coil coating finish was specified.

The existing doors were solid-core wood in wood frames complete with mill-finish aluminum storm doors. The wood doors swung to the inside of the unit, while the storm door swung outward to the balcony. This is a terrific setup for a mild day in spring with lots of ventilation and no thermal issues to address. However, in winter, they are woefully inadequate. A thermally broken aluminum frame, complete with a 44-mm (1 ¾-in.) thick insulated metal door, was the answer. In response to the wind pressures to maintain the seal around the doors, an out-swinging door was specified; to address the ventilation concerns, a vertically hung, insulating glass, sliding window with a flyscreen was set into the door. Accessibility concerns were also addressed by specifying a lever-type passage set, as opposed to the previously used knob set.

With the design and specifications determined, it was time to go to tender. A total of six qualified restoration firms with known experience in this type of work were invited to bid. The work was planned to occur in three phases over three years. When the tender closed at the site, the board selected the two low bidders and invited them to attend for an interview. This was a critical decision to take. When both firms are capable of doing the project, deciding which firm will be the best personal fit for the culture of the client is essential—especially if the project is going to last three years. As it happened, the low bidder was also determined by the board to be the best fit for the project team, and a contract was awarded to the contractor for $5.9 million.

With the project team in place, the process of ensuring ‘all oars were in the water and pulling at the same time’ began. This was referred to as the ‘mockup phase,’ and required the actual tradespeople who are going to carry out the work with products that are going to be used creating a full-scale representation of the finished project, and then subjecting it to testing.2 Time can be spent fretting over getting the detail drawings exactly correct, but if the person doing the construction work does not read the drawings or the specifications, it may not be good enough. For this project, a two-storey section of the building including corners, concrete, masonry, and windows was selected for the EIFS mockup. With attendance by the manufacturer, general contractor, installation trades, engineer, the board, and all others with an interest in the project, each step of the EIFS system could be reviewed in detail.

Since adhesive applied with a 13 by 13-mm (1/2 by 1/2-in.) notched trowel (i.e. notched adhesive) and mechanical fasteners were used in a ‘belt and suspenders’ approach to attachement, pull-out testing was conducted. The critical flashing details to ensure water within the system actually exits were reviewed and adjusted until the concept was understood. The base-coat protection to ensure the correct areas were left for sealants to adhere to were established and then sealants were tested to ensure adequate bond and flexibility. Finally, the colours and textures of the EIFS finish coat could be reviewed and approved by the condo board.

While the EIFS mockup was underway, the window and door mockup also proceeded. The process of tying the air barrier and drainage planes correctly into the existing building on one side and the new envelope on the other were painstakingly reviewed with the trades. The membranes were checked for proper lapping, and end-dams were installed. Drawing detail of fasteners were reviewed by the structural engineer, expanding foam was checked for depth and fill, interior painted wood jamb returns and casing finishes were installed, and once it was ready, the independent testing agency was called to confirm the CSA A440 specifications were met in-situ.

In this case, the windows instantly failed. This is why mockups and testing are done onsite—just because a manufacturer passes a test in a lab a few years ago, it is not enough to assume everything is still the same at the window plant. Of course, this type of event really tends to pique the interest of the manufacturers. In fairly short order, the source of the failure was determined and proper performance was confirmed by retesting again, onsite.

The combination of the new exterior insulating fi nish system (EIFS) and windows and doors effectively eliminates air-leakage.
The combination of the new exterior insulating finish system (EIFS) and windows and doors effectively eliminates air-leakage.

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Conclusion
As the time of this article, Phase 1 of the project is nearing completion and Phase 2 is gearing up. Concurrently with Phase 2, the aged, original heating boilers will be replaced with new, compact, high-efficiency models. Once completed, energy savings are forecasted to be up to 40 per cent. Coupled with the building’s new look and the absence of what had become the annual parade of repair trades, YCC 118 has made a major contribution to the value of its condo units and its profile in Toronto.

Notes
1 The full report can be accessed at www.daniels.utoronto.ca/people/faculty/publications/tower_renewal_guidelines. For another look at tower renewal, see the article, “Understanding Overcladding,” by Brian Burton, in the July 2011 issue of Construction Canada. (back to top)
2 A mockup is not intended to be insurance against failure to read contract documents. They are used to co-ordinate multiple interrelated trades’ work or confirm an esthetic result that may be hard to define entirely in contract documents. (back to top)

Brian - PhotoBrian Shedden, BSSO, is senior building envelope specialist at Entuitive Corporation in Calgary. He has more than three decades of experience in the restoration of existing buildings. Shedden is a past-president of the Ontario Building Envelope Council (OBEC), past director of Canadian Condominium Institute (CCI), presenter at Construct Canada, and recognized as a leading expert in the building envelope renewal field. He can be contacted via e-mail at brian.shedden@entuitive.com.

 

Jerry croppedGerald Genge, P.Eng., C.Eng., BDS, BSSO, C.Arb., Q.Med., is a consulting engineer and principal at GRG Building Consultant Inc. He has more than 35 years of experience, specializing in building assessment and rehabilitation. Genge can be reached at jgenge@grgbuilding.com.

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