R-value, U-value, G-Value



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R-, U-, G-value - What do I need to know?

The R-value is a measure of thermal resistance. The U-value is more used internationally and is calculated: 1/R-value. Resulting, the higher the R-value (the lower the U-value) the higher the thermal resistance. G-value measures the reflectivity of heat.

Apart from the excellent u-Values of our windows you can opt for better G-values to protect against heavy sun-radation, where necessary.


The dimensions of your window affect the U-value

This is due to the fact, that with every window there are 4 areas with different U-values. Remember: the higher the U-value the worse the thermal insulation,

1) The glass
2) The frame
3) The circumference of the glass
4) The circumference of the frame

Optimization of thermal insulation on our windows

The thermal insulation of glass is always better than that of the frame. We try to keep the dimensions of the frame as low as possible without endangering the stability to enxure the best thermal insulation.

However the proportions, the smallest windows will always have the worst insulation values. Every window is a "hole" in your wall, where in modern systems a U-value less than 0,01 is easily available. On the other hand this means, that a small window has a lesser insulation value but at the same time is a smaller "hole",

What remains important is the light and joy it will give you.

Example table

The table below gives you examples of our windows filled with Argon. To improve the insulation we offer a fill of the gaps between the window panes with Krypton.

Below the table you find the formula for the calculation of the values.

Example
U-values
Measurements
Width
(mm)
Height
(mm)
Amount
panes
Glass
Frame
Glass-
peri-
meter
Total
Glass
(m²)
Frame
(m²)
Surface
(m²)
Glass-
peri-
meter
Circum-
ference (m)
500 500 2
3
1,1
0,7
1,3
1,0
0,06 1,5
1,2
0,06
0,07
0,19
0,18
0,25 1,01
1,06
2,00
500 750 2
3
1,1
0,7
1,3
1,0
0,06 1,5
1,1
0,13
0,14
0,25
0,24
0,38 1,51
1,56
2,50
1000 1000 2
3
1,1
0,7
1,3
1,0
0,06 1,4
1,0
0,57
0,58
0,43
0,42
1,00 3,01
3,06
4,00
1000 1250 2
3
1,1
0,7
1,3
1,0
0,06 1,3
0,98
0,75
0,77
0,50
0,48
1,25 3,51
3,56
4,50
1500 2250 2
3
1,1
0,7
1,3
1,0
0,6 1,3
0,89
2,51
2,55
0,87
0,83
3,38 6,51
6,56
7,50

Argon/Krypton

These U-values are valid for our windows equipped with Argon. Glasses with Krypton can achieve an U-value of 0.5!
The formula:

Uw = (Ag x Rg + Af x Uf + lg x ψg) / Aw

Sounds complicated, but isn't, if you know:

Uw: U-value of window [m²]
Aw: Surface of complete window [m²]
Ag: Visible surface of glass [m²]
Rg: U-value of the mere glass [W/m²K]
Af: Surface of frame [m²]
Uf: U-value of frame [W/m²K]
lg : perimeter of glass [length]
ψg : Coefficient of loss due to thermal bridge of glass edge in W/m²K

W/m²K is the U-value

One has to add the length of the joint with the wall, which will be added with a lenth * ψe (Coefficient of loss due to thermal bridge). This value is determined by the way, how the window is built in and does not affect our table.

If you have any queries, do not hesitate to contact us.


 



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