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You Bet Your Glass: February 2013

No easy answers

February 13, 2013  By Frank Fulton

If you are an aluminum window manufacturer, curtainwall systems
provider, or commercial glazing contractor in Canada, your life has
become a lot more complicated recently, and this is only the beginning.

If you are an aluminum window manufacturer, curtainwall systems provider, or commercial glazing contractor in Canada, your life has become a lot more complicated recently, and this is only the beginning. If it hasn’t hit you on a job yet, don’t worry, it will. Hopefully this heads-up will save you some grief and a big loss.

Building codes across the country have changed or will be changing to ensure that all future buildings are constructed in a much more energy-efficient manner. Personally, I think the moves are in the best interests of all of us and our future generations. However, the guidelines, or the lack of them, for putting the code requirements into practice leave a lot to be desired. In Ontario, two major changes to the Ontario Building Code have taken effect within the past year. They are, Supplementary Standard SB-10: “Energy Efficiency Supplement,” and Supplementary Standard SB-12: “Energy Efficiency for Housing.”

SB-12 (at 27 pages the easier to follow of the two documents) deals only with housing excluding highrise construction. Besides providing compliance requirements for the entire building, it prescribes a U-value for windows and doors. That requirement on its own is easy enough for the window manufacturer or contractor to comply with, as using the National Fenestration Ratings Council’s thermal modelling tools to determine the U-value of a window or door product is a routine practice in the industry. However, the U-value of the windows or doors required to comply with SB-12 is a moving target and changes depending on a number of factors. The first is the location of the house within the province: is it in Heating Degree Days Zone 1 or 2? Next, is the type of heating system installed in the house natural gas or electric? The degree of efficiency of a natural gas heating system will affect the U-value required, as will the ratio of windows to wall area. Based on where all these variables fall, the required U-value of the windows can vary between 1.4 and two watts per square metre on centre – a huge range. Some well-designed, double-glazed, aluminum window products with upgraded thermal breaks and glazed with low-E glass and argon gas will only be in compliance for buildings in southern zones if the building is equipped with 90-per cent efficient natural gas heating and a window-to-wall ratio not exceeding 17 per cent. For other areas, or where the heating system is less efficient, or where the area of windows in the building is greater than 17 per cent, aluminum windows will most likely need to be triple glazed with two low-E coatings and argon, or glazed with heat mirror. Vinyl, fibreglass, or wood windows are capable of complying to most of the requirements depending on the glazing used. Northern zones require triple glazing.


As if using SB-12 weren’t complicated enough, SB-10 is a 113-page document designed for use by professional building engineers in the design of all buildings other than low-rise housing. It is used to determine the required U-value for the glazing in a building, but is well beyond the understanding of, and of little use to, most window and glass guys. As with SB-12, the U-value requirement for the glazing is a moving target determined by other factors.

So the problem facing window and curtainwall contractors is how to bid a project and be certain that they are in compliance with the building code. Most specifications do not clearly spell out the U-value requirements of the windows or curtainwalls, and the bidder will never know enough about the rest of the construction to determine what the U-value has to be. When bidding projects where a U-value is not clearly stated for the glazing in the specifications, ask that an addendum to the specifications be issued clearly stating the thermal requirements. If it is not, cover yourself by stating the U-value of the products you are proposing in your bid, with a qualification to your bid that you cannot determine compliance to the building code without further clarification from the architect. Otherwise, you will be on the hook for compliance after the fact, and this could end up costing you a lot of money to fulfil your contract.

Frank Fulton is president of Fultech Fenestration Consulting. He has been in the industry for 30 years and can be reached via e-mail at

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