Triple glazing Construction R-value

Questions, comments and suggestions about the Design Navigator R-value calculator

Triple glazing Construction R-value

Postby Jason Clark » Tue Mar 20, 2018 3:44 pm

Can anyone tell me what the 'construction R-value' is for triple glazing is which has an 'R-value' of 1.20 and U-value of 0.83?

Or am I getting confused and the U value is the same as a construction value?
its been about 12years since I had to do H1 calcs so I need to catch up a little
(but wow not much has changed in that time)

Im just trying to fill out the Branz Schedule method form which is asking for both an Insulation R-value and a Construction R-value
I have sent away to glazing manufacturer perhaps they can provide further info?
it is in the APL Klima series uPVC with aluclip
with 5mm low-e xcel, 16mm argon gas cavity, 4mm glass, 16mm argon gas, and 5mm low-e xcel
if that is of any help?
Jason Clark
 
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Re: Triple glazing Construction R-value

Postby Albrecht Stoecklein » Tue Mar 20, 2018 5:59 pm

Hi Jason,

The U-value is the inverse of the R-value.

Glazing manufacturers often only quote the "center of glass" R-value. That does not account for the frame. The total window R-value (including the frame) is sometimes called the construction R-value. That's the value you need to use for H1 compliance calculations.

In reality the construction R-value will of course depend on the window dimensions. In a very large window the frame will play a smaller role than in a very small window. So the quoted window construction R-values are based on a standardised window size (I believe 1.2m x 2m but I may be wrong). The R-values are also based on some standardised weather conditions because the R-value of a window will change depending on temperature, wind and humidity conditions.

So you should go back to the supplier and ask them for the standardised construction R-value of their windows. If they produce such advanced glazing systems they would certainly know what the R-value of the whole window is.

Hope that helps

Sunny regards

Albrecht
Albrecht Stoecklein
 
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Re: Triple glazing Construction R-value

Postby Jason Clark » Wed Mar 21, 2018 8:04 am

Thanks for that Albrecht, the other querey I had is howcome the Metro GlassTech / NZ WERS rating system effectively copied here has absolutely no mention of triple glazing units? I mean surely they must have been around for about 10 years in nz by now?
Jason Clark
 
Posts: 5
Joined: Tue Mar 20, 2018 7:32 am

Re: Triple glazing Construction R-value

Postby Albrecht Stoecklein » Wed Mar 21, 2018 10:54 am

Hi Jason,

I think 10 or even 5 years ago you would have to look very hard to find triple glazing in NZ. Even today there would be only a few specialist glazing companies or importers where you get triple glazing.

The WERS system was actually created about 15 years ago if I remember correctly, and has for years not being actively supported and extended anymore. I just quote the numbers here on my website because I found the system quite useful, but I don't have the simulation tools that would be required to calculate the performance of new glazing systems and to extend the product list.
Albrecht Stoecklein
 
Posts: 349
Joined: Sat Jun 13, 2009 5:30 pm


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