Before 2008 over 90% of windows and doors manufactured in New Zealand were single glazed aluminum windows. In 2008, new NZBC clause for energy efficiency H1 requires higher insulation of windows and doors. Now most new buildings choose thermally unbroken aluminum framed double glazed windows and doors to meet minimum building code requirement.
Although the change made in 2008 was a big step forward we are still well behind Europe and even some developing countries in terms of window insulation. For example minimum window R value in UK is 0.5, in Germany is 0.58 which is more than double than our minimum window R value of 0.26.
In a letter to BUILD magazine published in 2006, Ken Miller – a former President of the UK Federation of Master Builders wrote: ” After all, the Europeans have been building far longer than us and it’s about time we took a leaf out of their book. … Otherwise New Zealand will continue to build shoddy, leaking, damp and inefficient homes for years to come.” To download a full copy of his letter, click < Look to other countries to build wisely> .
PVC-U vs. Aluminum
Aluminum has been a widely accepted material used in window and door frame construction. Initially, it was thought to be a readily inexpensive alternative to wood framed windows and doors, performing with structural integrity while remaining friendly to the environment. Upon closer inspection, however, aluminum possesses many characteristics that make it unacceptable in the construction of modern windows.
In the pre-treatment of aluminum, many toxic chemicals are used throughout the process of creating window and door profiles. Chromate baths for rinsing the bare metal prior to priming and painting, acrylic and polyester enamels used to paint the bare aluminum, and nickel acetate used to create protective anodized coatings, have all been labeled toxic or carcinogenic by the Occupational Safety and Health Administration ( OSHA ). If not closely monitored and controlled, these chemical agents can cause illness and death from prolonged exposure. Studies have shown that aluminum in the environment can affect the growth of beech and spruce trees, as the many by-products of production attack their fine roots.
Alternative materials do exist that can counteract the spread and use of these toxins in our environment. PVC-U is durable, readily available, and has many added features that aluminum could never match. More importantly, the process used in creating PVC-U windows and doors yield only water vapour into atmosphere. No harmful chemicals or toxins are dumped into our surrounding rivers and streams. Also, any PVC-U not used in the manufacturing plants can be recycled into other useful products. PVC-U replacement and new construction window products minimize waste and environmental harm as they provide one of the most efficient building materials used today. Through years of development, PVC-U has become the smart alternative to aluminum.
Atmospheric conditions won’t affect PVC-U
Aluminum won’t rust, but it will corrode. Even painted aluminum surfaces will nick and scratch from constant external weathering or daily internal operation. Corrosion can cause discoloration of the window surface and eventually window failure. Aluminum also experiences electromechanical effects from many different sources that are found in everyday living. Lawn fertilizers, salt air and industrial pollution can cause an aluminum window system to become unsightly and undependable. Also, because of its inherent thermal conduction properties, aluminum windows can cause a condensation build-up in the interior of the home. If unchecked, this condensation can run off the window surface causing damage to interior fabrics, wallpaper, and wood surfaces.
PVC-U windows are not affected by the weather or air pollution. Salt air, acid rain, industrial pollution, pesticides, lawn fertilizers, smog and other air contaminant’s that are normal to everyday living cause no discoloration or structural damage to PVC-U windows. Interior condensation is a fraction of what builds up on aluminum windows and usually evaporates before any damage may occur inside your home. PVC-U windows and doors won’t rot, chip, peel or flake. PVC-U windows and doors won’t warp or fade, so your windows will always operate properly and retain their good looks.
PVC-U windows in fires
PVC-U exhibits excellent fire behaviour and it does not burn once the source of heat or flame has been removed.
PVC-U is very difficult to ignite using commonly available ignition sources (match, blow lamp etc.). Tests with a wide variety of sources varying in heat intensity and impingement area on PVC-U window frames show that the product only burns whilst the source is applied. When the source is removed there is no residual flame on the product. In terms of ignitability, the temperature required to ignite PVC-U is more than 120oC higher than that of pinewood (385oC for PVC-U and 260oC for wood as defined for self-ignition). Once a material has been ignited the flammability can be defined in terms of the Limiting Oxygen Index (LIO) test. This defines the amount of oxygen that needs to be present for a material to burn freely. A material with an LIO of 21 will burn freely in air (which contains 21% oxygen) and one with an LIO of more than 21 will not burn in air at room temperature. PVC-U has an LIO of about 50, compared with the wood LIO of 21. This shows that PVC-U will not sustain combustion in air at room temperature and is better than wood in this test.
The limited burning of PVC-U is confirmed in a variety of other standard fire tests, which measure specific parameters such as rate of heat release and flame spread under different conditions.
Smoke is the result of incomplete burning of a material and consists of solid or liquid particles in the combustion gases. Smoke densities are similar to wood under smouldering conditions but greater under flaming conditions. The combustion gases (e.g.. HCl) may lead to some corrosion of metallic materials but restoration is normally possible. The corrosion gases have no effects on the structural elements of buildings. The toxic potency of the combustion gases of PVC-U is similar to and certainly not significantly worse than those of many natural materials. The build-up of toxic fumes will be slow compared with rapidly burning materials of a similar toxic potency.
The rate of generation and quantity of smoke and fumes produced by a PVC-U window will depend on the severity of the external source applied. The smoke and fumes emitted will be confined to the area of the product affected by the source and their transport away from the impingement zone will depend on local factors such as ventilation and survival of the glazing.
For more technical information about PVC-U windows and doors, visit TANGRAM TECHNOLOGY Ltd ( www.tangram.co.uk ) – Consulting Engineers for Plastics Products in the UK.
Some extreme environmental campaigners are seeking to position PVC (polyvinyl chloride) as an environmentally damaging material. However, when subjected to close scientific scrutiny, their claims are left stranded, allowing a quite different picture, one which underlines the sound environmental and technical performance of PVC – to emerge.
Please click < Windows – A Transparent Case for PVC > , published by BPF (British Plastic Federation) aimed at correcting the misinformation, given by many NGO’s, on the sustainability and environmental safety of PVC-U windows. Or click < PVC-U Windows and the Environment > , published by BPF/PIFA.