uPVC Windows for New Zealand Conditions
The Window Association of New Zealand welcomes manufacturers of all material types into its membership. Common materials that windows and doors are made from include timber; metals such as aluminium, bronze, stainless steel; composites such as Fibreglass; and plastics such as uPVC.
The purpose of the Window Association is to ensure the windows manufactured by its members, regardless of what materials they are made from, meet all the relevant performance Standards, including durability. Other important performance standards are strength, weathertightness and air leakage.
What is the WANZ UPVC Specification for NZ?
The “Specification for uPVC Window Profiles for the Fabrication of Windows and Doors” is a simple performance requirement based on two well-used International Standards EN 12608 and EN 513.
As the normal EN12608 “severe climate” test is approximately equivalent to 2 years outdoors exposure in the New Zealand climate, further modification is needed to approximate the minimum 15 years durability requirement of the New Zealand Building Code.
The modifications to the above standard tests are to either:
a) adjust the solar radiation dosage (sunshine) onto the sample being tested so that it represents the level of solar radiation that New Zealand has. In all other respects, the test is identical to that used in Europe.
This option provides manufacturers with the easiest compliance route.
and / or
b) change the formulation of the uPVC blend so that it has a minimum level of 8 parts per hundred resin, (8phr) Titanium Dioxide acting as a sunscreen to protect it from the damaging UV light.
This option is based on the knowledge and experience of the uPVC manufacturing industry in New Zealand over the past several decades for other uPVC construction products. The New Zealand sunshine strength requires a higher level of “sunscreen” in the formulation mix to protect the uPVC from the strong UV light we have in New Zealand.
What is 8 phr?
uPVC formulations express additives (such as Titanium Dioxide) as so many parts per hundred parts of PVC resin (phr).
This ensures that the critical parts of a formula are always in balance with one another, even if other parts of the formulation might vary.
What is Rutile?
Rutile is the most common natural form of Titanium Dioxide. It is the type that has the highest stability, and also the highest reflective index – i.e. the best type for reflecting the harmful UV light away from the uPVC so that the uPVC is not quickly destroyed by sunlight.
More about uPVC for windows
Like all materials, PVC has both good points and not so good points to consider.
PVC is a man-made plastic which contains PVC mixed with several other ingredients to produce the final plastic material that becomes the uPVC profiles that some window frames are made of.
The “U” means it is unplasticized and, therefore, more rigid than the very soft, plasticised PVC that your kitchen floor vinyl is made from. The rigidity of uPVC window frames is usually improved in the factory by inserting metal stiffeners into the window frames before they are assembled. It is extremely important that the uPVC framing is stiff enough to withstand the extreme wind pressures that occur during stormy weather. The connection of the individual stiffeners inserted into the uPVC is also very important.
All windows, including windows made from uPVC, must be tested and certified as complying with the requirements of NZS 4211:2008 for residential low rise, or NZS4284:2008 for high rise buildings and Specific Engineering Design. Windows and doors may have been tested to other European Standards (or Standards from other countries) but these are not automatically appropriate or acceptable for New Zealand conditions.
Mixing uPVC is just like mixing a cake at home – you need high quality ingredients of the right type for a good result.
Where does our uPVC come from?
All plastic window profiles are imported into New Zealand, as the low demand for uPVC windows does not justify manufacturing the plastic locally. With hundreds, or maybe thousands, of PVC suppliers worldwide, all making their own “mix”, it is vital that the New Zealand consumer has very high confidence that the “mix” they are buying is a good one.
The role of the Window Association is to tap into the worldwide PVC expert knowledge-base and produce a uPVC Standard that is suitable for New Zealand conditions.
How the uPVC Specification for New Zealand was developed:
New Zealand also has the history of some imported uPVC windows and siding (cladding) that failed in a few short years. These products have been quite satisfactory in the countries they were formulated for, but in the harsh New Zealand climate with its high UV levels, they have failed.
Plastics Industry Support
The Window Association of New Zealand appreciates the support provided by local uPVC manufacturers who understand the needs of formulating uPVC for the New Zealand climate and strong sunlight. These, and other plastics industry experts, have no commercial interest in plastic windows as all the uPVC profiles for windows continue to be imported. Their concern is that uPVC does not fail in any application, as that would damage the reputation of the New Zealand plastics industry.
The National Institute of Water and Atmospheric Research undertook research to advise on the uPVC Specification so that it is appropriate for New Zealand conditions and will meet the requirements of the NZ Building Code.
NIWA noted that, in New Zealand, the UV radiation is relatively more intense than at corresponding latitudes in the northern hemisphere. After downgrading the testing requirements to consider the generally milder NZ temperatures (compared to Europe), NIWA advised that the “Severe” test requirements of the EN Standard should be required.
NIWA also noted that uPVC profiles that have been tested to comply only with the European Standards are not necessarily suitable for use in New Zealand. NIWA therefore recommends the addition of the “sunscreen” (Titanium Dioxide) into the formulation mix to protect the plastic (refers only to test option b).
If you are purchasing uPVC windows or doors, make sure the windows come with a certificate of compliance with this uPVC Standard for New Zealand conditions.
The complying product may be a little more expensive than other uPVC windows – but it will be well worth it!