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What is a good R-value for windows in New Zealand?

A good R-value for a window in New Zealand is R0.5 to R0.7.

For the lower South Island, a good R-value would be R0.8.

You can achieve this with:

  • Thermally broken aluminium windows with good Low-E double glazing
  • uPVC windows with low-E double glazing
  • Timber windows with Low-E double glazing
  • From 2008-2022, the New Zealand Building code required a minimum of R0.26, which was achieved with “cold” aluminium frames and clear double glazing. As of November 2022, this will no longer be acceptable under the New Zealand Building Code H1/AS1.

How do I know the R-value for my windows?

The R-values of windows are made up of two important factors, both of which you can ask to change or specify.

  1. The R value of the frame, and
  2. The R value of the glass.

(Also note that you may come across “U” values for the frame and glass – more on that on another blog post! In short, R values and U-values are the reciprocal of each other, so if you divide the 1 by the U-value, you get the R value, and vice versa).

One measures how much energy gets through the window, and the other measures how much energy is blocked.

Different glass can be put with different frames to get the values you desire! It is very important to ask your builder or window company about this, because their default is almost certainly not the best outcome for you, even if it might be the cheapest.

How can I compare the R-values for different frame and glazing types, and the costs?

The below chart shows common frame types combined with the common glass types. It also shows where the New Zealand Building Code regulations sit.

Window R Value Infographic
Window R value Performance guide Infographic for aluminium, thermally broken aluminium, uPVC and timber windows according to the New Zealand Building Code

Stärke can offer aluminium frames, thermally broken aluminium frames, and uPVC frames; contact us today regarding your project.

But what about the different costs?

We can send you the same chart with our pricing estimation overlaid on it – in high resolution or as a PDF! Give us a call or email


The below chart contains the same information in a different format – you can sort and filter to choose the best combination of frame and glazing for your project. The data shown is as per the New Zealand Building Code H1/AS1, Table E1.1.1.

FrameGlazing TypeR-Value
AluminiumUg 2.63 Clear/Clear (Air) (Double)0.26
AluminiumUg 1.9 LowE1/Clear (Argon) (Double)0.3
AluminiumUg 1.6 LowE2/Clear (Argon) (Double)0.33
AluminiumUg 1.3 LowE3/Clear (Argon) (Double)0.35
AluminiumUg 1.1 LowE4/Clear (Argon) (Double)0.37
AluminiumUg 0.9 LowE4/Clear (Krypton) (Double)0.4
Thermally Broken AluminiumUg 2.63 Clear/Clear (Air) (Double)0.32
Thermally Broken AluminiumUg 1.9 LowE1/Clear (Argon)(Double)0.39
Thermally Broken AluminiumUg 1.6 LowE2/Clear (Argon)(Double)0.42
Thermally Broken AluminiumUg 1.3 LowE3/Clear (Argon)(Double)0.46
Thermally Broken AluminiumUg 1.1 LowE4/Clear (Argon)(Double)0.5
Thermally Broken AluminiumUg 0.9 LowE4/Clear (Krypton)(Double)0.54
Thermally Broken AluminiumUg 1.89 Clear/Clear/Clear (Air) (Triple)0.38
Thermally Broken AluminiumUg 1.2 LowE2/Clear/Clear (Argon) (Triple)0.48
Thermally Broken AluminiumUg 1.0 LowE3/Clear/Clear (Argon) (Triple)0.52
Thermally Broken AluminiumUg 0.7 LowE3/LowE3/Clear (Argon) (Triple)0.59
Thermally Broken AluminiumUg 0.6 LowE4/LowE4/Clear (Argon) (Triple)0.62
uPVCUg 2.63 Clear/Clear (Air) (Double)0.4
uPVCUg 1.9 LowE1/Clear (Argon)(Double)0.5
uPVCUg 1.6 LowE2/Clear (Argon)(Double)0.56
uPVCUg 1.3 LowE3/Clear (Argon)(Double)0.63
uPVCUg 1.1 LowE4/Clear (Argon)(Double)0.69
uPVCUg 0.9 LowE4/Clear (Krypton)(Double)0.76
uPVCUg 1.89 Clear/Clear/Clear (Air) (Triple)0.5
uPVCUg 1.2 LowE2/Clear/Clear (Argon) (Triple)0.66
uPVCUg 1.0 LowE3/Clear/Clear (Argon) (Triple)0.73
uPVCUg 0.7 LowE3/LowE3/Clear (Argon) (Triple)0.86
uPVCUg 0.6 LowE4/LowE4/Clear (Argon) (Triple)0.91
Timber Ug 2.63 Clear/Clear (Air) (Double)0.44
Timber Ug 1.9 LowE1/Clear (Argon)(Double)0.56
Timber Ug 1.6 LowE2/Clear (Argon)(Double)0.63
Timber Ug 1.3 LowE3/Clear (Argon)(Double)0.71
Timber Ug 1.1 LowE4/Clear (Argon)(Double)0.77
Timber Ug 0.9 LowE4/Clear (Krypton)(Double)0.85
Timber Ug 1.89 Clear/Clear/Clear (Air) (Triple)0.56
Timber Ug 1.2 LowE2/Clear/Clear (Argon) (Triple)0.74
Timber Ug 1.0 LowE3/Clear/Clear (Argon) (Triple)0.81
Timber Ug 0.7 LowE3/LowE3/Clear (Argon) (Triple)0.95
Timber Ug 0.6 LowE4/LowE4/Clear (Argon) (Triple)1.01