Why is uPVC so special?

uPVC windows (also known as vinyl windows) has been replacing wood and aluminium window frames across the world since the 1950's because of it's improved thermal insulation, durability, and physical properties.

uPVC windows now account for over 60% of all residential window sales in the USA. The balance is mostly wood, not aluminium. Even thermally broken aluminium won't meet the US minimum R-Value of 0.58.

uPVC Is An Exceptional Insulator

One major reason for its increase in popularity is because uPVC is an insulator, unlike aluminium. It helps keep your home more comfortable by minimizing heat transfer through your joinery and minimizing (often eliminating) condensation on the inside of the window frame.

Look at the heat transfer rates in the table. As you can see, aluminium is a terrible insulator and transfers >1000 times more heat than uPVC.  Aluminium's fast heat transfer is the reason why it is used for frying pans and other cookware!

Material Heat transfer*
Gold 318
Aluminium 237
Glass 1.11
uPVC 0.19
Fiberglass .045
Polystyrene (styrofoam) .040
Air .026
Argon .016
Vacuum 0.00

* (W.m-1.K-1)

Let's Compare

Below is a comparison of average awning window thermal performance for aluminium frames, thermally broken aluminium frames, and our multi-chambered standard uPVC frames.

R-Values are commonly used to measure the insulating properties of materials with the higher R-Value being a better insulator.

Window thermal performance comparison.
Thermal performance comparison of different window types

Standard ThermaScreen uPVC windows can save up to 80% heat loss compared to single-pane aluminium windows

What are you waiting for?

uPVC Windows & Doors Are Incredibly Popular Overseas

In other countries, uPVC is the most popular residential window material. In the US, over 60% of all new windows are uPVC, and that percentage is rising. The balance is mostly wood with some composite.

An independent construction consulting firm Principia states the reason is that "uPVC and composite windows include lower cost which can be half the cost of wood, scratch resistant, reduced warping, and eliminating the need to repaint. Although many alternative materials offer these features, pricing can be a major tiebreaker among selection criteria."

Comparison of uPVC windows
Window Materials by Percentages. Total Units in Millions (MM).
Modern Black uPVC Windows with Transom

uPVC Is Also Very Durable

You can expect incredible longevity and high resistance to natural elements, unlike wooden or aluminium joinery.

When wooden and aluminium windows are exposed to moisture, boring bugs or salt air, you will see changes to the look of the windows. Over time, the structural integrity of the joinery will weaken.

However, uPVC is completely immune to rot. It doesn't corrode even when exposed to salt water. It is impervious to bugs and never needs to be repainted.

Even scratches are hard to see because the exterior colour matches the interior. There's simply no colour 'coating' or paint to scratch off.

Added Strength Of Welded Corners

All Pella uPVC windows have welded corners. These welds are strong and durable, and completely weather resistant. The welding of multiple chambers within the frame (see above) also help resist warping and twisting due to external forces.

This makes a strong window that is more durable and withstands the rigours of everyday usage.

uPVC Welded Corner
Double Hung windows with transom and Integrated Insect Screens

Did you know, all ThermaScreen windows come with seamlessly integrated insect screens?

Whether you prefer the NZ traditional awning style, casement style, or horizontal or vertical sliding windows that eliminate injuries to those walking outside of the home, all windows come standard with integrated (not after market, upgrade, or magnetic add-on) insect screens.

Addressing The Old "uPVC UV Stability" In NZ Excuse

Historically, uPVC products have a marred reputation concerning UV exposure. Over 30 years ago, a number of uPVC products were imported from Europe, mainly siding. They didn't stand up well in the NZ sun because NZ has more UV exposure than Europe. The main reason for the higher UV in NZ is that NZ is closer to the equator (~35°S) and has more direct sunlight than Europe which is closer to the pole (~50°N). However, regions that are even closer to the equator than NZ have more UV than NZ. This includes all of the southern US states (18-25°N). Here is the scientific proof of this from NZ and world experts.

That being said, the southern US states have been installing uPVC windows for 40+ years and not had brittleness or UV issues because the formulation used in the US is different than Europe and has considerably more 'sunscreen' protection.  All suppliers of uPVC windows in NZ need to meet formulation requirements for UV exposure set by the Window and Glass Association of New Zealand – in fact, building plans and permits wouldn’t have council approval if they didn’t.

Unfortunately, New Zealand’s outdated knowledge and hearsay around uPVC UV stability means Kiwis haven’t been enjoying the insulating benefits of these windows, which vastly out-perform (even) thermally-broken aluminium. We’re certainly working to educate and advocate for change – so are our customers who now have warmer, drier homes.

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2 thoughts on “Why uPVC?”

  1. Hi there. How does pvc go with our high UV we are exposed to here in NZ. Somewhat different than he US i would. I welcome feed back. Had a friend just deal with you and gave you top marks.

    1. Thank you for your question. UV stability of our uPVC is our most commonly asked question.

      This question most often comes from comparing the UV exposure in NZ to that of Europe (from where most international experience comes to NZ). New Zealand has more UV light than Europe mainly because NZ is closer to the equator than Europe and therefore we receive more direct sunlight. Previously, uPVC products from Europe have not always stood up to our higher UV. For this reason, there are different and more strict requirements on uPVC products in New Zealand to ensure that they meet the E2 durability requirements in the NZ building code. All of our uPVC products meet or exceed these requirements. More information on this topic and a document that certifies that our uPVC windows, as manufactured by Pella, meet these requirements can be found here.

      Please keep in mind that we import our windows from the US, not Europe. The southern US states are actually closer to the equator than NZ, get more direct sunlight, and have HIGHER UV exposure than NZ. Therefore, the US uses a different formulation of uPVC that incorporates more ‘sunscreen’, and our windows have 40+ years history of exposure to higher UV levels than experienced in NZ and are still going strong.

      The fact that the lower US has more UV than NZ may come as a surprise to some. If you would like a second, third, or even fourth opinion, I encourage you to see the UV exposure blog that contains scientific data and proof of these claims here.

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