More rigorous energy performance standards for windows and doors proposed

Windows and doors in the net-zero frame

National Energy Code pushes the envelope toward low-carbon performance
Thursday, February 27, 2020
By Barbara Carss

A wider selection of high-performance windows and doors is expected to hit the market as Canada’s National Energy Code continues to push the envelope toward net-zero-energy-ready development. A new slate of proposed code changes, released for public review earlier this winter, include downward adjustment of permitted thresholds for heat loss through the building envelope and air leakage at the juncture of building components and assemblies. Developers and designers adhering to the code’s prescriptive path would also face stricter constraints on the number and/or size of windows in almost all of Canada’s climate zones.

While there will still be leeway to fall short of some requirements via the code’s performance path, which factors in counterbalancing tradeoffs elsewhere in the building design, the proposed updates will narrow the room for such manoeuvring. Industry insiders suggest the pending 2020 iteration of the energy code will pose more challenges for developers and designers than the previous 2017 version, and prompt window and door manufacturers to respond.

“I think the smart manufacturers realize this isn’t the time for baby steps,” muses Al Jaugelis, technical director with Fenestration Canada, the national association for window manufacturers and distributors. “These kinds of code changes are signalling to the industry: It’s time to upgrade your platform.”

He predicts market demand will pick up for triple-glazed commercial products such as storefront windows and building entrances that are now primarily sold as double-glazed configurations. Meanwhile, a proposed reduction of U-values for thermal transmittance, or the movement of heat from inside to outside, will most directly affect windows that are designed to be opened because they typically sport twice as much metal as fixed, inoperable windows.

“The highest performing part of a window or door, the part that gives you your efficiency, is the glass. The worst performing part of any window or door is the framing system,” Jaugelis explains. “In most of our market, we don’t have a big supply of operable windows and doors that can achieve this (proposed U-values).”

Lower U-values bring upfront costs and long-term operational savings

As proposed, allowable U-values — a measure of heat loss over surface area per degree Celsius of indoor-outdoor temperature differential, which is expressed in watts per square metre per kelvin (W/m2-K) — for doors and vertical windows will drop by varying amounts in all six of Canada’s climate zones. A complementary code change would introduce higher allowable U-values for skylights to recognize that their sloped formation alters how heat transfer occurs, but wouldn’t diminish performance expectations.

“The proposed skylight U-values will result in a skylight with the same physical components (i.e. low-e coatings, gas fills and warm edge spacers) as a window that complies with the lower U-values,” states the accompanying code change rationale from the Canadian Commission on Building and Fire Codes (CCBFC).

CCBFC projections, based on modelling of 16 archetype structures in the six climate zones, show a range of resulting upfront cost premiums and energy saving estimates. In general, added costs will be highest in climate zones 7A and 7B, covering much of the populated area of northern Quebec, northern Ontario, Manitoba, Saskatchewan, Alberta and northern British Columbia.

That’s pegged, on average, at $12,900 to $14,000 or a 2 to 2.2 per cent premium compared to compliance with 2017 code criteria. The same zones would reap the greatest energy savings, modelled at 94 to 114 gigajoules (GJ) or 2.4 to 2.8 per cent annual savings compared to performance of the 2017 U-value thresholds.

Nationwide, large office development would see the largest incremental cost increase, estimated at an average of $25,900 or 2 per cent compared to 2017 criteria, which would deliver a projected additional 178 GJ or 1 per cent annual energy saving. However, gains could be somewhat muted depending on seasonal intensity.

“The proposed reduction in window thermal transmittance results in reduced heating, but increased cooling. The better insulated windows reduce heat loss during the winter, but prevent cooling during summer nights/mornings,” the code change rationale acknowledges.

Supporting Canada’s clean growth and climate change commitments

In any case, Jaugelis speculates developers and designers will have to balance off superior performance of some window products for the non-compliance of others. That practice, known as area-weighted averaging, has already been employed to meet standards invoked in 2017 and 2015 editions of the energy code.

“The threshold at which you have to take those measures is now moving downward so this may affect some designs and development that wouldn’t have been affected before,” he says. “For fixed windows, with triple glazing, you can meet these (proposed) numbers. As you get to operable windows, it starts becoming almost impossible, although you might reach those numbers in the lowest climate zones, in places like Vancouver and Windsor.”

That’s arguably in harmony with the code’s overarching agenda to achieve net-zero-energy-ready (NZER) status by the end of this decade — a goal set out in the Pan-Canadian Framework on Clean Growth and Climate Change to support Canada’s commitment to reduce greenhouse gas emissions by 30 per cent below 2005 levels by 2030. It’s a challenging target that many building specialists agree requires a steady and aggressive schedule for improvement.

The CCBFC’s code change rationale confirms the proposed new U-values are aligned with driving 15 to 20 per cent better energy performance than the baseline of the 2017 energy code. Accordingly, Jaugelis sees evidence the emphasis on steady improvement is achieving results in the fenestration sector.

“The products on the market today are significantly improved in terms of energy performance from what they were 10 or 15 years ago, and the same will be true 10 years from now,” he predicts. On that front, further advances in thermal break technology will be key if operable windows are to deliver stricter U-values.

“The reason fixed windows more easily comply today is because they have less metal, more glass, but we use the same thermal break design in fixed and operable products,” Jaugelis advises. “I think a sophisticated manufacturer will look at the trend of the code going to net-zero and try to get out ahead of it.”

Codifying available products and common practices

The rationale for other proposed code changes related to windows and doors points to products and practices that have already been adopted in the market. That includes more stringent standards for allowable air leakage of doors, revolving doors and overhead doors, and reduction of the permitted ratio of windows and doors to overall wall area (given the acronym FDWR for: fenestration and door to wall ratio) in most of Canada for new construction built to the code’s prescriptive path.

The code change rationale calls the existing code allowance for door air leakage “excessive” and argues that “typically readily available doors in the market today” can meet more rigorous standards. Currently, the air leakage threshold is 0.5 litres per second per square metre (L/s-m2) for conventional doors and 5 L/s-m2 for the revolving and sliding doors serving as commercial property entrances, while proposed code changes would lower those thresholds to 0.3 L/s-m2 and 2 L/s-m2 respectively.

“Reducing the allowable air leakage rate for doors will encourage manufacturers to develop and produce more efficient products,” the code rationale submits.

“The trend to higher performing products has been occurring for some time, and manufacturers that engineer and produce these products tend to lead the market,” agrees Mike Plecash, general manager with Canadian Doormaster Ltd. and president of the Canadian Door Institute, an association representing manufacturers, dealers and distributors. “If we are going to develop effective strategies to deal with climate change, certainly developing high-performance products must be part of this.”

Proposed FDWR adjustments vary across climate zones and actually allow for an expanded proportion of windows and doors in climate zones 4 (Victoria) and 5 (Greater Vancouver, Niagara Region and Windsor). Code drafters maintain the new ratios will reduce thermal transfer through the building envelope, thus curbing the energy load for heating and cooling and saving capital costs for HVAC equipment and the envelope itself.

“Fenestration is typically an expensive element of the above-ground building envelope and, in some cases, is more costly per unit area than opaque above-ground building assemblies,” the code change rationale states. In line with that argument, it observes that many recently constructed buildings have a lower window-to-wall ratio than the current prescriptive path allows.

Nevertheless, new prescriptive ratios will be immaterial for a lot of the booming development in major Canadian cities.

“High-rise condo builders almost always use the performance path largely because condos would rarely fall within the required window-wall ratio for the prescriptive path,” notes Andrew Pride, an influential contributor to the energy code in his role as chair of the National Research Council’s Standing Committee on Energy Efficiency in Buildings.

“Developers and architects have a whole lot of tools in their toolbox,” Jaugelis concurs. “The window and door products you use in the building are just one element of the energy management strategy.”

All proposed changes to the National Energy Code are open for comment until March 13, 2020. Once an updated version of the code is finalized, Canada’s provinces and territories will have to adopt it into their own building codes before any new measures could go into force in those jurisdictions.

Barbara Carss is editor-in-chief of Canadian Property Management.

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