7 Durability Considerations for uPVC Windows in New Zealand for Better Buildings

New Zealand’s diverse climate, ranging from the sunny North to the icy deep South, presents a huge durability challenge for most construction materials. When it comes to window frames, surviving in the face of varying temperatures, high humidity, and exposure to intense sunlight is paramount. In this context, uPVC (unplasticized polyvinyl chloride) emerges as a standout material, offering exceptional performance for New Zealand homes. Below, we will explore:

Just how harsh is our sun, rain and wind?

Lets talk UV. That’s what fades our furniture, gives us dreaded sunburn, and cracks and fades any materials which are not up to the specification. 

NZ does experience high UV from the sun, but the amount we get is actually on par with most of the southern hemisphere, including Australia, South America, and the UAE. See the picture on the right from NIWA showing peak UV amounts over the world.

And then there’s weather extremes: uPVC is renowned for its resilience against extreme weather conditions. Unlike traditional materials such as wood, uPVC does not rot, warp, or corrode when exposed to rain, humidity, or salty coastal air. This resilience ensures that uPVC window frames remain robust and functional over the long term. The STARKE Ambiance suite also has multi-locking points and double rubber seals for supreme performance against the elements, and co-extruded seals, meaning that they will not pull away in the corners like aluminium systems do.

And here in New Zealand, a tiny island in the pacific, many of our locations are coastal, which means they are exposed to salt-laden air, which can be corrosive to certain materials. uPVC’s corrosion resistance makes it an ideal choice for window frames in these regions. The material does not succumb to rust or corrosion, ensuring longevity and durability, even in the face of challenging environmental conditions (check out your corrosion zone here). And our hardware is rated and tested to the same standard they use on oil rigs. So it’s pretty good then.

But old PVC windows in NZ didn’t last?!

Yes, that’s right. There was an era of PVC windows brought into NZ that weren’t up to standard. And that’s left a bad taste in our mouths. 

Around 20 years ago, PVC windows (note the exclusion of the ‘u’) were imported made-to-size from UK and Europe. The manufacturers were unaware that their products were being shipped to New Zealand – with much tougher UV rays – likely because they were purchased through a ‘middle-man’ who didn’t pass the info on.
As a result, the manufacturers made the windows from the same profiles they used to supply their local customers (makes sense, doesn’t it!). But once here in NZ, it didn’t take long for the products to fail.

Change for the better

When the manufacturers mentioned above began getting complaints from down here in NZ, they, firstly, were a little surprised they weren’t told where it was going, and secondly, they could fix it. And that’s exactly what they did. 

They created a new formula for the profiles, which includes titanium dioxide, (the sun blocker used in sunscreen) among other things. Then they called it the ‘hot country’ mix, and that is what we manufacture, especially for NZ.

The addition of the ‘u’ in uPVC came at a similar time, although from a separate cause. That ‘u’ stands for un-plasticised, and basically means that there are no chemical plasticisers in the profiles. Plasticisers make things flexible and malleable, which is what we don’t want for window frames – they need to be strong and durable, which are exactly what uPVC frames are. Plasticisers are also the nasty chemicals which “off-gas” on new PVC products – interestingly, this is what is responsible for the smell in a new car, and that funny smell of a kids paddling pool when you first unbox it. It’s not very good for you. The removal of these plasticiers from window frames was a big leap forward for the industry. 

New Zealand tends to follow what happens in the UK, Europe and America, although a decade or two behind. uPVC windows and doors have been the go-to choice for about 50 years over there, while we have been stuck on cold aluminium frames. We believe there is change coming, and uPVC is the future of joinery in NZ.

When uPVC frames are being manufactured, long strands called polymers twist around each other providing strength. But it doesn’t stop there. Impact modifiers are added which bind to the polymers providing even more strength. In the end, the result is a surface hardness equal to aluminium. This makes uPVC a hard and tough material and much more durable than just PVC, as you might be thinking. uPVC is also non-toxic and BPA-free, which makes it popular in the medical industry!

uPVC windows are easy to clean too. They are low-maintenance and they don’t rot, corrode or rust – perfect for your seaside house!

STARKE Ambiance uPVC frames are German engineered and supplied and the hardware is directly from Europe too. All being manufactured here in Aukland NZ, giving you local made quality windows. This means we can offer a high thermally performing, highly air tight, very secure window and door solution, improving our lives and the lives of all future generations. Why not have the house you wanted to grow up in, or the one you want to grow old in?

How does uPVC compare to aluminium?

There is no two ways about this. Both systems fill a hole in your wall with glass, but the comparisons stop there.

We know how easy it is to think of both aluminium and uPVC as doing the same job, but there is more at play. Here at Starke, our roots are in aluminium, so we know exactly what it is like, however we think that NZ deserves warmer, more efficient homes, and this the way to do it.

Lets talk about aluminium windows now. Aluminium is also strong and durable, but it is the powder coating that is exposed to the sun not the aluminium, so just how durable is that? Well, the powder coating process is interesting. Firstly, some plastic sheets are made in the desired colour, then they are ground up to a very fine powder. This powder is then sprayed onto the aluminium and melted on to form, you guessed it, a plastic skin over the aluminium.  In that regard, uPVC frames won’t fade any more than aluminium powder coating. And there is the upside that, if the frame gets scratched, there is not shiny silver aluminium underneath, so the scratch will be a lot less visible.

The largest difference has to be the thermal performance of uPVC windows and doors compared to aluminium systems available in NZ – even thermally broken ones. We care about building performance, and with STARKE Ambiance you can experience a much more controlled environment in your home, that is easier to heat and cool and stay like that, whatever it is like outside, reducing your energy bills at the same time – genius! (not really, just good windows and doors)

Enough talking, how do we prove it?

It is important to have a clear understanding of what we’re talking about when it comes to uPVC windows durability, and there are four important differentiations to make:

  1. Expected lifespan of uPVC windows in New Zealand, which is 40-50 years.
  2. NZ Building Code B2 durability requirement of uPVC windows in New Zealand, which is 15 years.
  3. Slight fading of uPVC windows in New Zealand, which does not affect performance and happens with all building products
  4. And finally, manufacturers warranties, which for STARKE Ambiance uPVC windows, is 10 years.

Expected lifespan

Firstly, the expected life-span of 40-50 years is the anticipated duration that uPVC windows are designed to endure without significant deterioration. This considers factors such as material strength, resistance to weathering, and overall structural integrity over a prolonged period. It should be noted that this is a subjective topic, and can be compared with the 8-12 year expected lifespan of a new car, even though we see many cars on the road at double or triple this age. Your Ambiance uPVC windows will be the same, and could last indefinitely if well maintained. The expected lifespan is a design consideration, but not accounted for in the building code.

Building code B2 Durability Compliance

Interestingly, the New Zealand building code only sets a 15-year durability requirement for some construction materials, including all windows and doors. This standard ensures that the material maintains its functionality and structural integrity for at least 15 years.  This makes compliance relatively easy, as a product expected to last 50 years sails through these requirements. 

Non-critical fading

It’s important to note at this stage that in the harsh NZ sunlight, that slight aesthetic fading is to be expected for any exterior building product. This is true of aluminium powder coated windows and uPVC windows are no different, emphasizing the durability of uPVC even in the face of natural weathering processes. This slight fading, which occurs on roofs, claddings, gutting and everything else between, does not affect the performance or durability of the window system. 


Lastly, the 10-year warranty period serves as a commercial commitment to the durability of uPVC window frames. Manufacturers typically offer this warranty to assure customers of the product’s quality and performance, providing coverage for any unforeseen issues during the initial period of use. It should be noted that different manufacturers have varying levels of faith in their own product, and sometimes this is represented in shorter warranty times. In our car metaphor, this is similar to the common 3 year warranty found on new cars.

Demonstrating Compliance

Ok, so having understood what we’re talking about, we can move on to the three primary methods of demonstrating the durability requirements and compliance for uPVC windows in NZ, and these are:

  1. Compliance with accelerated UV ageing requirements, in a lab or in the field.
  2. Minimum percentage of titanium dioxide declaration
  3. In-service history

UV Exposure aging

The second method involves subjecting uPVC samples to ageing through concentrated or natural weathering UV exposure. This can simulate the impact of years of sunlight exposure in a condensed timeframe, allowing researchers to assess real world durability. This method provides valuable insights into the material’s resistance to discoloration, degradation, and other UV-induced effects, offering a predictive measure of its long-term durability in New Zealand’s intense sunlight conditions.

The UV ageing compliance is the one used by the uPVC Window Alliances’ industry code of practice (ICP) in Australia. It is likely that this, or something similar to it, will be adopted in New Zealand.

This accreditation goes beyond the weathering standards typically applied to profiles for other regions such as northern or southern Europe, the US or China.  For example, under the European standard EN12608, the typical radiation exposure used to test profiles is 8000 MJ/m2. This is suitable for windows being used in northern Europe. EN 12608 also has a ‘Severe’ climate test for warmer parts of Europe which exposes profiles to 12,000 MJ/m2. The new Australian ICP requires testing to a minimum of 15,000 MJ/m2.

Starke Ambiance uPVC Profiles after 36 months of continuous exposure showing no degradation
Starke Ambiance uPVC Profiles after 36 months of continuous exposure showing no degradation
Arid Test Site: Extreme heat

Allunga Exposure Laboratory operates an arid exposure site in north-western Queensland approximately 500 km west of Townsville (75 km Nort-West of Huhgenden). This site is characterized by low humidity, low rainfall, high radiation and large daily temperature variations. This area can experience up to 50 C heat, and regularly receives 40 C + over many months.

Titanium Dioxide

The third method employs a quantitative approach, demonstrating compliance through a specific quantity of titanium oxide in the uPVC formulation. Titanium oxide is a key additive known for enhancing the UV resistance of uPVC. By establishing a standard concentration of titanium oxide in the material, manufacturers can ensure a consistent level of UV protection, thereby reinforcing the durability and compliance of uPVC window frames. This method combines precision with material science to create a formula that withstands the rigors of New Zealand’s climatic challenges, offering a reliable and quantifiable measure of compliance.

In-Service History

The first method, in-use history, relies on the premise that if a material has demonstrated longevity in real-world applications, it is likely to be durable. This approach involves examining the performance of uPVC window frames over an extended period, considering factors such as weather exposure, temperature variations, and general wear and tear. And fortunately, we have just this experience; there have been uPVC house lots manufactured since the early 2000’s, mainly for renovations and refurbishment, by smaller manufacturers. These windows are all still going strong!

So, what does this all mean?

uPVC has been used as the primary window and door material in many developed countries for a long time, establishing it as a well proven system which can stand up to the elements. And its now available in volume in NZ! 

Our Ambiance uPVC profiles have been, and will continue to be, extensively tested and proven around the world in climates similar to (and ones with higher UV also) New Zealand, with many industry professionals endorsing them. In short, the Ambiance uPVC system is suitable for long exposure to NZ conditions, and we will continue to ensure this so you don’t need to worry about it.