PVCU Windows
Is PVCu the most toxic synthetic material to contaminate the environment man has invented or is it a safe material for window frames and superior to wood or aluminium?
In this article I am going to tell you what pvcu windows are, address the debate about whether they have a negative or positive effect on the environment, discuss their performance and compare it with the alternatives of timber and aluminum, and finally draw some conclusions and offer some advice.
pvcu Windows What Are They?
Let me quote Thermalframe, a company in New Zealand, which supplies pvcu windows. Here is their website http://www.epcsheerframe.co.nz/
“PVC windows, PVCu windows, uPVC windows and vinyl windows are the same thing – PVC windows. People from the USA or Canada tend to call them vinyl windows, people from UK / Europe tend to call them UPVC, or PVCu windows. With regard to strength of PVC windows, the vinyl windows of USA/Canadian origin tend to be lighter with less wall thickness than their UK / European counterparts and therefore are a little less suitable for the size of windows we tend to build in New Zealand. Either way, advancements in the polymer industry has seen these take over the world.”
“PVC stands for Poly Vinyl Chloride. The ‘u’ means that the PVC is unplasticised, i.e. rigid. PVC is a major thermoplastic material used in a wide variety of applications and products. The essential raw materials for PVC are derived from salt and oil. The electrolysis of salt water produces chlorine, which combine with ethylene, obtained from oil, to provide vinyl chloride monomer (VCM). Molecules of VCM are polymerised to perform PVC resin, to which appropriate additives are incorporated to make a customised PVC compound. PVC can be plasticised to make it flexible for use in flooring and vital medical products for example, or rigid “PVCu”, the U stands for “unplasticised” – which is used extensively in building applications including window frames.”
pvcu Eco Friendly or the Devil in Disguise?
For many people the major problem with vinyl is the negative effect its production and incineration has on the environment. The process creates significant toxins, including dioxin, one of the most toxic compounds known. For this reason, vinyl windows are often discouraged for “green” projects. Joe Thornton a research scientist at Colombia University wrote a paper in 2005 outlining the dangers and toxins associated with pvcu which can be found here:
http://www.healthybuilding.net/pvc/ThorntonPVCSummary.html
As you might expect Thermalframe, a company which distributes pvcu, window frames have a robust defense. Let me quote their website (which is http://www.epcsheerframe.co.nz/)
“Thermalframe is as conscious of the environment as you are.”Green” is not a fad; it is a way of life we must all adapt if our children are to have the same quality of life we now enjoy. The environmental impact of any product must be measured from cradle to grave, taking into account the impact of each phase of its life cycle. PVCu is a safe choice in all phases. PVCu requires substantially fewer resources to produce than metal alternatives. When PVCu is used as a substitute for wood precious hardwood forests are spared… the plentiful, replaceable pine is not suitable for windows. It would take quite a few hardwood trees to replace the 20-25 million PVCu windows installed in Britain. PVCu joinery lasts longer and needs little maintenance and no painting. The long life means fewer resources are needed to replace it later and the low maintenance spares the environment exposure to harsh chemicals involved with preservatives, paint and associated solvents. It is an environmentally friendly product composing 55% salt and is recyclable. Thermalframe PVCu joinery is all made from organic calcium based profiles and are completely lead-free.”
At the Centre for Alternative Energy in the UK (a registered charity) they have come down firmly in favour of wood. It’s interesting that Thermalframe the main proponents of PVCu windows only talk about PVCu being preferable to hardwoods and they may be right. But there are many other sustainable sources of timber frames. This is what the Centre for Alternative Energy say:- (here is a link to the full paper I am quoting from http://www.cat.org.uk/information/pdf/GlazingOver.pdf )
“Timber, uPVC or aluminium frames? If you are replacing windows, wood is the best option. There are many environmental problems associated with the manufacture of PVC. High levels of dioxins and other organochlorines are found around PVC plants and are released to the atmosphere on combustion. They’ve been linked with cancer, immune system damage and hormone disruption. Although manufacturing techniques are improving, disposal at end-of-life is still a problem.
PVC manufacture uses lots of energy; far more than wood production. Wood frames can last for over 50 years, and then be renovated rather than replaced. uPVC windows usually need replacing after a much shorter period. Although uPVC window manufacturers claim they are maintenance free, Dulux recently brought out a uPVC frame paint, recommended for use every 6 years! Aluminium manufacture involves a lot of energy use and pollution. The coatings on some frames make recycling difficult – not ideal for such a high value material, so look for anodized frames if you do choose aluminium.”
Another problem with pvcu is that it is relatively weak so the frames have to be quite thick reducing the glazing area and transmitted light. So pvcu isn’t suitable for large windows on this account alone. Another problem is vinyl’s tendency to expand and contract with normal temperature fluctuations which can cause loosening of seals and corner cracks.
Certainly aluminium frames on their own are not appropriate because they conduct heat with great efficiency and where used there are problems of condensation forming on the frame. However aliminium is strong and can be combined with wood or vinyl in a number of different ways to incorporate thermal breaks. These pictures illustrate how:-
http://www.efficientwindows.org/ftypes.cfm
The key message here is that the most earth friendly option is wood. The material comes from sustainable sources and it’s a strong low maintenance material. So for “green” projects wood is best. Aluminium is an option too where it is blended with other material to incorporate thermal breaks. The principal advantage is its strength for large windows.
So wood is best and the best timber framed windows are manufactured in Scandanavia where you can source splendid prefabricated ecologically friendly windows including triple glazed argon or krypton e-coated windows at reasonable prices.
Other Key Components in Energy Efficient Glazing
- Fitting: the quality of the seal and the workmanship here is critical to the performance of the window and the energy performance of the building. This is the most important factor of all. A bad window system well fitted is probably better than a good window system badly fitted. So be wise in your choice of fitter and by the way this applies to the whole building.
- Window panes: this is a massive area I will address in another article.
- Shading and Shutters: also a critical factor in the overall performance and the subject of another article.
- Placement and Orientation: also a key factor in the energy balance of the building.
And finally
Windows used to be considered the inevitable weak point in insulating your home. But with significant changes in technology over the last twenty years which allow light to pass through but not heat (or sound) this is no longer the case. Indeed these days you can have it all. You can have enormous windows which are pointed at the best views and you can have the internal layout that you want without compromising the energy efficiency of the building. It’s a question of getting the energy balance of the building right and a key part of this equation is the glazing. Watch this space for more information.
This article was written by John Wolfendale a director at Eco Vida.
