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Community and Q&A

What do these window ratings mean : I-55, A3, B5, S2, F10?

homestead-windows | Posted in Energy Efficiency and Durability on

Windows with these ratings I-55, A3, B5, S2, F10 were recently installed in our building. Do you know what these ratings mean?

The landlord has made an application to increase the rent to a whopping 5.5% based on this capital expenditure (and other lower cost expenditures).

Previous windows were double paned and I’d like to know what benefits windows with ratings of I-55, A3, B5, S2, F10 have over previous double-paned windows.

Our hearing is this Friday July 19.

Also the wind load resistance increased to C5. What does this mean?

Please help. Thanks so much!

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  1. Expert Member
    Dana Dorsett | | #1

    Without knowing the ratings of your prior windows, it's hard to know what (if any) benefits of the new windows had over the prior units. The basic meanings of all that alphabet-soup can be found here:

    In order:

    I-55 indicates middle-of-the road insulated glazing with low wintertime condensation potential. It probably does not have a low-E coating on the interior-most surface nor multiple low-E coating,s but likely has at least 1 coated surface inside the sealed glass and possibly argon fill rather than air or dry-nitrogen. If the older windows were clear-glass with nitrogen/air fill it's going to be a heating/cooling energy-saver.

    A3 is the most air-tight of the CSA categories- you'd have to dig elsewhere to find what the test conditions are to meet that grade.

    B5 is the high-middle range for water tightness under CSA test conditions.

    S2 indicates it's a bit harder to open & close (often the case with tighter weatherstripping.)

    F10 indicates a middle-of-the road resistance to the ease of breaking in through a latched or locked window from the outside.

    C5 is the best CSA class for wind-load resistance.

    I've never reviewed the CSA window test specs, can't tell you much more detail than that, but it might be available surfing the CSA website. The ER ratings of the new windows would be of interest too, if available.

  2. homestead-windows | | #2

    Thank you so much Dana. That's a wonderful detailed and helpful reply.

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