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Thread: Question on design standards relating to window transparency

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    Cyburbian graciela's avatar
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    Question on design standards relating to window transparency

    It seems that our downtown design standards have an unrealistic reference to window transparency. Our requirements outline a certain percentage of tint as the maxium.

    These standards are fairly new and I have just had the chance to review a project and the tint of the glass has come into question. The problem is that the glass specifications do not call out the percentage of tint. I am guessing that the tint percentage is better applied to automobile window tint and is not an acceptable measure for architectural glass? The specs for the glass to be used in the project I am reviewing have numbers for UV transmittance and such.

    Have any of you encountered this?
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    NIMBY asshatterer Plus Richmond Jake's avatar
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    I'm trying to wrap my little brain around this one, so help me. Maybe these are stupid questions but, 1) Why would a business want to tint their windows to obscure their products, and 2) What legitimate public purpose is served regulating the transparency of windows (other than perhaps security)?

    What am I missing here?

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    Cyburbian graciela's avatar
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    Well this started with the design standards. They are pretty new and I am finally getting to break them in one some downtown projects. A group of stakeholders worked for 2.5 years to develop them. They wanted to make sure that any downtown businesses including offices had transparent windows. They also wanted to prevent a glass building from being built downtown. The section in the standards on transparency requirements has percentages called out based on character areas. The language in that part is generic and just says transparent.

    When you get to the section on building materials it gets more specific. Mirror glass and tinted glass with a tint of 20% gray or greater are prohibited. This is the really problematic section. In window tint speak, 20% is considered very dark with 5% being limo tint. This is because the 20% is the amount of visual light transmission. It seems that the stakeholders were thinking of more of a gradient where 20% would be the darkest shade of gray allowed. Another issue is that the glass that is being used comes in gray, green and warm bronze. The project is going with gray but I wonder if because of the phrasing they could use green and do whatever they want with the % vlt?

    So now do I end up interpreting the code backwards from how it is written and require a minimum of 80% vlt until I can get it amended?

    I know this sounds very nitpicky but I am trying to make sure these new design standards are enforceable and as straightforward as possible.
    Last edited by graciela; 30 Jul 2008 at 10:43 AM. Reason: clarification
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  4. #4
    Cyburbian
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    WOW that's specific. It does sound as though the project could go with green, hard to tell w/out looking at cut sheets etc though. What was the intent of the stakeholders to go with percentages of tint, anyway? You could probably get the same result by just requiring a minimum percentage of transparent/translucent glazing based on the overall size of each facade, and prohibiting or limiting spandrel, without having to get into analyzing the tint and visible light transmission.
    I don't dream. I plan.

  5. #5
    Cyburbian graciela's avatar
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    This whole things seems so silly to me the more I think about it. I am starting to feel a bit stupid.

    From what I understand, the stakeholders wanted to keep the glass from being too reflective and making sure that pedestrians could see into the spaces from the street. They were not terribly successful in reaching their goal. I also wonder if 80% is too light? I am looking at spec sheets for architectural glass and only 3 of the types have that degree of VLT. The average seems to be about 70 and that is for the clear glass. None of the tinted glass approaches that. The greatest VLT is 69%. The proposed glass has a VLT of 35% and is not so dark but is more reflective than I imagine a glass with higher VLT would be.

    Oh, and the spandrel glass is a whole 'nuther issue. That is also part of this project and we are trying to figure out how to deal with it too. The vague specificity in the design standards is killing me.
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    Cyburbian Raf's avatar
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    This is really interesting. When we write DT guidelines we include transparency, but in relation to building facade and the amount of glass windows, not the reflective tint into it. However as we go towards more "green" standards we are beginning to use tint as a percentage, but this is dealing more with "R" values reflecting UV rays more so than anything else. Can you still contact the consultant or group that wrote this for some more insight?
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    Cyburbian graciela's avatar
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    I would love to build some sustainability into these design standards and throughout our code. Amending this portion might be a good place to start.

    I think we are going to try and get the citizens advisory group (mastermind behind these standards) back together and explain some of the challenges that we are facing with implementation. I hope that I can get enough guidance to neaten up the language and ensure that we are still allowing the creativity to keep our downtown eclectic. We have a lot of safe archictecture going in right now if you get my drift.
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    Cyburbian Raf's avatar
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    Gotta avoid the bland stucco somehow. There are ways!
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    Cyburbian graciela's avatar
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    Thankfully, stucco is limited to 25%, no artifical stucco allowed at all. We actually have a brick problem.

    I don't like that our design standards disallow metal as a material. There are some really cool metal materials out there that perform well, are sustainable and look good. How would you allow those but keep the bad forms of metal out?
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