How to determine the thickness of an IGU


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Old 09-20-21, 01:53 AM
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Post How to determine the thickness of an IGU

Hi there,
I am trying to create some technical drawings of windows for an LCA study where I will be comparing 3 different window frame materials, but to make the study more accurate I want the thickness of the IGU to be the same.
But to do this I need to know how thick the IGU of the window should be.
I was wondering how one determines the thickness of this?
I understand that there are different types of IGU out there such as; low-e, low-e2, bronze, argon or krypton filled, double pane, triple pane, aluminum spacer, swiggle spacer. And these must each have ceretain attributes that make them optimal for specific scenarios - is there official documentation that defines their specific uses to help me choose which one to go for?
Also does U-value, R-value and G-value come into helping make the decision? - if so are there equations? and again is there any documentation/ standards which show this?
(the project is uk based so maybe uk documentation or standards are best, but anything would still be better than nothing.)
I suppose a better question of what I am asking is: When window companies are tasked with providing windows for a project such as that outlined below; how do they choose what IGU to use and how do they know what thickness is should be?
The project is located in Aberdeenshire, Scotland and this means the average monthly temperatures are quite low, (see attached image)


so therefore good insulation and higher solar gain I assume would be a focus. Sound dampening wouldn't be an issue as the project is rural and also security would not be of utmost importance.
If there is anymore information that may be of assistance please let me know.
Thanks in advance for any help!
 

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09-20-21, 06:09 AM
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It's a strange question and probably not something we can adequately answer. The thickness of an IGU is determined by the window manufacturers design, and nowadays they typically need to meet a minimum energy standard. See the tables in this USA document, where minimum standards for window fenestration change based on location (climate).

https://www.energystar.gov/sites/def...ments%20v6.pdf

You would obviously need a document specifically covering Scotland's energy requirements, and since this forum is US based you aren't likely to find what you are asking here... your best bet would be to talk to your local building inspectors / departments.

Here in the US, commercial IGU's are almost always 1" thick, and while there are many common thicknesses for residential, you often see 3/4", 13/16", 7/8" in residential. In the past many were 1/2" or 5/8" but its hard to achieve minimum energy standards with an IGU that thin, because the closer 2 pieces of glass are, the more thermal bridging there will be, and the less efficient it will be. But the thinnest glass possible is usually what is preferred from a design aspect. So that's why design comes in. A window company will usually design a window that is going to have a frame that is wide enough to accept an optimum size of IGU that will meet today's typical minimum energy standards, or better.
 
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Old 09-20-21, 06:09 AM
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It's a strange question and probably not something we can adequately answer. The thickness of an IGU is determined by the window manufacturers design, and nowadays they typically need to meet a minimum energy standard. See the tables in this USA document, where minimum standards for window fenestration change based on location (climate).

https://www.energystar.gov/sites/def...ments%20v6.pdf

You would obviously need a document specifically covering Scotland's energy requirements, and since this forum is US based you aren't likely to find what you are asking here... your best bet would be to talk to your local building inspectors / departments.

Here in the US, commercial IGU's are almost always 1" thick, and while there are many common thicknesses for residential, you often see 3/4", 13/16", 7/8" in residential. In the past many were 1/2" or 5/8" but its hard to achieve minimum energy standards with an IGU that thin, because the closer 2 pieces of glass are, the more thermal bridging there will be, and the less efficient it will be. But the thinnest glass possible is usually what is preferred from a design aspect. So that's why design comes in. A window company will usually design a window that is going to have a frame that is wide enough to accept an optimum size of IGU that will meet today's typical minimum energy standards, or better.
 
johnam, Ludio B voted this post useful.
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Old 09-20-21, 10:17 AM
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Hi XSleeper,
Thanks for you response, that is very helpful to understand the process of how the dimensions of the IGU and frames come to be.
I have also infact just now come across the exact piece of documentation that I was looking for.
It is the British Standard:
'BS 6262-1-2017: Glazing for buildings. General methodology for the selection of glazing.'
I acctually came across it completely fortuitously but it couldn't be more ideal for answering my question if it tried!
 
 

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