By Tracy Hanes
Climate-resilient construction measures are coming to a code near you
The City of Toronto earned a dubious honour on June 23, 2025. As the mercury hit 36°C, with a record-breaking humidex of 46°C, it made the list of the world’s hottest major cities.
On July 16, 2024, 10 cm of rain fell in just three hours, drenching the GTA and causing massive flooding that blew past $1 billion in insurable losses, with total costs likely three to four times higher, according to the Insurance Bureau of Canada. The Ottawa area, meanwhile, bore the brunt of a May 2022 derecho—a widespread, long-lived, straight-line windstorm associated with a fast-moving group of severe thunderstorms—that caused $720 million in damage in Ontario. Both events were among the top six most costly natural disasters in Canada in terms of insurance claims, according to Catastrophe Indices and Quantification Inc. (CatIQ)., Canada’s loss and exposure indices provider.
Extreme climate events such as these aren’t anomalies.
“I keep hearing, ‘Is this the new normal?’ But it’s just the start of how things will be,” says Ryan Zizzo, founder and CEO of full-service climate consultancy Mantle Developments, and a professional engineer with extensive experience in climate-smart construction project management.
Adding to that concern is the fact that 1.5 million homes, or roughly 10% of Canada’s houses, can’t get insurance due to their locations, according to Dr. Blair Feltmate, head of the Intact Centre on Climate Adaptation (ICCA) at the University of Waterloo.
“This is a huge deal for insurance companies, and they are hoping to get others on side to mitigate the risks,” says Gord Cooke, president of Building Knowledge, which helps builders and developers design and construct homes with improved performance and indoor living environments.
Zizzo says there’s pushback from some home builders’ associations, as they view climate resilience as one reason why housing is so expensive. Still, many of those measures might soon be mandated. And many are trying to get ahead of the curve.
“There are some builders that have started down this (resiliency) path, and the Canadian Home Builders’ Association has launched a task force with the Institute for Catastrophic Loss Reduction to find evidence-based solutions, as some day, this will be in the Code,” says Cooke.
Currently, the OBC is roughly 85% the same as the National Building Code, Cooke notes. The latest published, but not yet adopted, edition, NBC 2025, does include a few new resiliency measures; however, it is unclear whether the OBC will adopt those sections, Cooke adds.
Feltmate, Zizzo and Cooke all say there are measures builders can take now to make homes more resilient, some at little cost. The ICCA has developed a series of infographics that address climate-related perils, including fire, flooding and heat, with cost-effective measures that builders and homeowners can incorporate into new or existing homes.
As it stands, homeowners are paying dearly for climate change in more than one way, with premiums climbing much faster than inflation. The average cost of a typical homeowner policy in Ontario now runs about $1,565 per year (≈ $130/month), according to Rates.ca. Premiums in the province jumped 84% between 2014 and 2024, then another 5% in Q1 2025, on top of double-digit increases for many 2024 renewals. And, as Global News reports, the 5.3% average hike projected for 2025 is more than twice the Bank of Canada’s 2% inflation target.
Flooding
Of course, that all pales in comparison to climate-related damages. “The average flooded basement costs $54,000 to remedy,” says Feltmate. “It’s non-negotiable that you have to spend that money. If you experience a flood on Monday and it remains unresolved by Wednesday, the house is deemed uninhabitable. It’s not discretionary spending.”
Depending on the market zone, homes with sump pumps should have battery backup and electrical panels that can easily be converted to run from a generator, advises Cooke. A kit from Home Depot costs about $500, Feltmate notes—a small price to pay given the average cost of basement flood damage.
Builders may want to reconsider building basements altogether and instead build up into the attic, Cooke suggests. His son has an older 1940s house near the Humber River that has experienced multiple basement floods, and if he rebuilds, he won’t include a basement.
One proven mitigating technology is the green roof, a standard the City of Toronto has had in place for 15 years. Noting that these roofs reduce flooding by absorbing rainfall, while providing a habitat for birds and insects, Zizzo believes that green roof standards “should be rolled out across the country.”
In the interim, new-home builders should avoid building on floodplains, Feltmate stresses. There are 36 areas in Ontario where conservation authorities regulate building, but in other regions, it’s at the discretion of the municipality. But Ontario’s newly passed Bill 17 will limit conservation authorities’ role in development approvals, and “that can be very dangerous, because perhaps you have a mayor who doesn’t believe climate change is real, or councillors who have lived there for 25 years and have never seen a drop of water in their basements,” Feltmate says. “Cheating the system is catching up, though, and that’s why 1.5 million homes in Canada are not insurable. In Quebec, Desjardins has stopped renewing mortgages for homes in flood areas.”
And expect it to get wetter. Environment and Climate Change Canada confirms an upward trend in heavy precipitation across Southern Ontario: intense rainfall events that once occurred every 10 years are now happening every five years or less in many regions. Large urban centres such as Toronto, Ottawa and Hamilton report increases in one-hour and two-hour rainfall extremes—key drivers of flash floods through overwhelmed storm sewers and urban runoff systems. Municipal water authorities, meanwhile, report more frequent and intense drainage backups and basement flooding, even during what were once considered moderate rains.
Wind
According to the Insurance Bureau of Canada, wind caused $340 million in insured damages across Ontario in 2024. Doug Tarry Homes is, shall we say, blowing away the competition when it comes to mitigating potential damage. The St. Thomas-based builder has participated in a pilot project with The Institute for Catastrophic Loss Reduction, aimed at enhancing home resilience to high-wind and tornado events, with a focus on the roof. At 100 new homes in St. Thomas, Tarry installed measures based on extensive research led by Western University, one of which involved longer roof sheathing nails and a second involving a special screw connecting the roof framing to the walls.
Company president Doug Tarry has witnessed the devastation that extreme weather events can wreak. As co-founder of the charity Hope Agua Vita, he helped rebuild homes in Puerto Rico that were destroyed by Hurricane Maria in 2017. It provided valuable insight into how to build more resilient homes in Ontario.
Measures on roofs provide the highest benefit at the least cost, says Tarry. He says hurricane ties aren’t costly, but it takes one minute to install one. A six-inch hurricane screw, on the other hand, can be installed in eight seconds. “You have to factor in the cost of labour,” he cautions.
Underlayment is another measure the company has taken, so that if shingles blow off, the roof still has some protection. “We’ve redesigned our gable overhangs too, as a high wind effect rips them up and water comes in,” Tarry explains. “We tie it back to the truss. We build the structure on the ground and crane it up. It’s more resistant to uplift and won’t sag. It’s standard with our homes, and we’ve shared this with the industry.”
While roof-to-wall hurricane ties and screws are not yet in the Code, and need to be more cost-effective for most builders, they’re standard in all Doug Tarry homes.
Despite the costs of resiliency, Tarry says his company has “done well” in the current market and met its targets for new-home sales. Net Zero Ready (NZR) homes offer significantly lower operating costs and are more resilient than OBC homes, with features such as a tighter envelope, low-solar-gain windows, and superior air filtration systems that help mitigate the effects of high heat events and wildfire smoke. Homes upgraded to full Net Zero could potentially store power from their solar panels in a battery to provide power during an outage. Tarry’s homes are either fully electric or dual-fuel hybrid models, which help reduce carbon emissions that contribute to climate change.
“Lots of builders are pulling back on Net Zero/NZR and Energy Star because of the cost,” Tarry notes. “But that’s not a choice we’ve made. We have customers come to us because of our better-value product. We’re a little bit boutique and have chosen a different path. Someone has to get out in front and figure out how to do it. That’s our role, and we’re happy to share what we’ve learned.”
Fire
Wildfires are not just a western Canadian problem, notes Feltmate, as Ontario’s boreal forests are at risk. “Areas such as Muskoka, Haliburton and the Kawarthas are vulnerable, and it’s just a matter of time before there’s a major wildfire in southern Ontario,” he says. “We should be preparing for this now.”
The ICCA, for its part, suggests solutions such as integrating 30-metre-wide zones, or fire breaks, with ignition-resistant materials, including mowed grass, roads and ponds, into community design. Builders can consider using fire-resistant building materials such as Class-A roofing, non-combustible siding and non-combustible decking materials.
With regard to landscaping, Tarry cautions, “No wooden decks, and no shrubs around the foundation perimeter in fire-interface zones. And there should either be no eaves, or they should be covered.”
A growing concern in Ontario has been wildfire smoke. Protecting against pollutants such as those from wildfires is one of the reasons Zizzo believes there also needs to be more effective air filtration in buildings.
Heat
Extreme heat is also of concern to Feltmate, who says that between 2050 and 2080, the average summer temperature is expected to increase by three to five degrees above current temperatures. Furthermore, the number of hot summer days per summer is increasing throughout southern Ontario.
While most new-home builders don’t currently install AC in new homes as a standard feature but make provisions for it, “We’re starting to see a movement to make air conditioning a requirement,” says Zizzo, who believes it should be mandated in the NBC, noting that a 5,000 BTU window unit costs only $150 and will typically last 10 years, incurring about $5 a month in added hydro costs during the summer.
“Houses are getting much hotter, as builders are putting in way more windows that have 50% heat gain,” Cooke says. “This becomes even more problematic if there’s a lot of west-facing glass without proper shading or overhangs, or wall-to-wall glass that leads to a whole new level of air conditioning.” And if there are power outages, “you’re going to have a problem in a tall building.”
Other measures could include awnings, strategic placement of trees, and storm shutters that protect against heat and wind.
Current and Future Code Measures
Simply building to NZ/NZR or Passive House standards includes resiliency elements such as highly insulated building envelopes, high-performance windows and air filtration. Cooke says the first step for builders is to simply follow well-documented methodologies, such as proper water management for roofs, walls and basements—elements that have been in the Code for at least 25 years. For example, it’s well-known how to anchor roofs. “We know about screws and how to install them on rafters. These measures are in the Code but are not being enforced. You need best-practice guides, and you need training, such as how to properly install windows.”
Cooke says the Local Energy Efficiency Partnerships (LEEP) program, managed by Natural Resources Canada, is one resource builders can access for training and guidance.
While Canada’s next building code, set to take effect in 2030, will incorporate climate resilience for the first time, few details have been released yet.
Municipalities Taking Steps
At least 14 Ontario municipalities, including Toronto and Markham, have adopted green building standards that incorporate some resiliency measures, although Ontario’s Bill 17, as mentioned, will limit cities’ ability to set their own green standards.
At the Community Resilience Recognition Day during the 2024 National Climate Adaptation Summit last October, cities making exceptional strides were highlighted. Hamilton Housing was honoured for its Ken Soble Tower in the category of Resilient Housing. Earning Passive House Canada EnerPHit Certification, the 2017-to-2021 transformation rehabilitated a post-war apartment tower to reduce greenhouse gas emissions by 94%. It laid the groundwork for industry-wide, ultra-low-energy retrofits needed to maintain and upgrade apartment buildings.
The tower features R38 overcladding and Passive House windows. Its Juliet balconies offer enhanced natural light and improved natural ventilation, reducing reliance on artificial lighting and heating and cooling systems, and avoiding the thermal bridging that conventional balconies can cause.
Dufferin County, meanwhile, was recognized at the event for its Hurricane Clip Rebate Program in the Disaster Resilience and Emergency Management category. “Normally, we think of how walls hold a roof up. In a severe storm, we need to consider how the walls will hold the roof down,” the county notes. The rebate program provides property owners with $4.50 for each installed and inspected hurricane clip used to secure the roof rafters or trusses to the top plate of the wall on your new construction project.
These thin metal straps (or ties) may have the word “hurricane” in their name, but they could just as easily be referred to as tornado clips. Ontario, Canada’s most active tornado zone, averages 18 tornadoes per year, according to Western University data. There were a whopping 60 last year, however, 10 of which occurred over water, according to the Northern Tornadoes Project. Most are rated EF0 or EF1 on the Fujita scale (98% of all tornadoes in Canada measure EF-2 or less, with winds less than 252 km/h). That’s the sweet spot where Tarry’s measures can make all the difference.
Feltmate says almost every major city in Ontario offers weather-mitigating subsidies that you can direct homeowners to, such as for disconnecting a downspout from the eavestrough to divert water away from the foundation, or for installing backwater valves.
“The backwater valve installation costs about $2,800 to $3,000, and 70% is covered in most Canadian cities,” Feltmate advises. “Ten to 15 years ago, people were unaware of their existence, or they were difficult to find on a website, or too complicated. Cities are now making the process more user-friendly and better advertised. But a lot of people don’t use them, and the uptake has only been 7-9% so far.”
The Next Moves
On a broad level, the next steps require “cooperation between insurance companies, municipalities, builders and different levels of government. There has to be a carrot and stick,” Tarry says. For example, insurance companies could provide a reduced rate for homeowners who incorporate resiliency measures into their homes.
Zizzo calls for provincial guidance on climate-smart construction, as he says the OBC currently contains nothing related to carbon footprint or climate resiliency. The federal government has a good climate policy, he notes, but the province hasn’t adopted it.
In the meantime, Tarry recommends taking proactive measures. “Determine the highest (climate-related) priority in your area, and work at getting good at that detailing,” Tarry says. “High-fire interface area? Look at non-combustibles. High potential winds? Keep the roof on! High flood or rain potential? Keep water away from the home.
“But for all homes, the two commandments are moisture management and airtightness.”
“When you don’t do sustainable and resilient design up front, it becomes more expensive in the long run,” Zizzo cautions. “Things you can do to the roof and basement are a small investment, with large savings in the long term.”
Cooke is also an advocate of hedging against the future. “Do I think these measures will end up in the Code in 10 years? Yes.”
“The good news is that, to a large extent, we know what the problems are and have developed very good guidance in Canada with various agencies, providing practical, cost-effective advice,” Feltmate says. “The problem is, we need to deploy these solutions and preparedness much more rapidly. There’s not much we can do when a house is on fire or a basement is full of water.”
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