What type of window is most eco friendly? It’s clearer than you think

If you have read any of the other posts on this blog you will know that Laura and I have quite a few decisions to make regarding which businesses we engage to supply us with products for the renovation of our house.  Literally all aspects of the building need updating.  In this post I thought I would jot down our thoughts on the topic of windows / glazing…

The current choice of material for windows and doors, in expected order of popularity across the UK is, PVCu, aluminium, solid wood, engineered wood and steel.


Some writers have suggested that steel has little to recommend it. Its thermal performance is cited as being poor, the cost high and its embodied energy equally high. Unless there is a structural need (a listed building or something similar, there is likely to be a better alternative.  I have read somewhere to that although is a recyclable material, when it is powder-coated (usually the case for windows and doors) it is practically non-recyclable.  I need to check in with Space Shuffle on this point as we had talked about windows made of wood with an exterior aluminium facia.

In the UK PVCu has been the defacto standard for most new builds and refits for quite some time, presumably as it is relatively cheap product that is perceived to be long-life and maintenance-free.  Cheap maybe, but considering it’s degrade speed of plastic, why to glazing businesses fit such poor hinges and seals.  The windows in our house are really not that old and the plastic appears fine, but corrosion of the hinges and general poor quality of the mechanisms means that we have had to re-align and force close some of the units and keep them locked for fear of not being able to open them again!

In addition to questionable quality (which ultimately does relate to environmental impact ) PVCu units use large amounts of fossil fuel in their production, they also use other chemical additives.  However The Building Research Establishment has recently accepted that PVCu is a recyclable material. However, there are no post-consumer PVCu recycling facilities in the UK, it just goes to landfill.

If steel and plastic are off limits and aluminium when coated is not recyclable the only choice we might be left with is wood.  In the past it has had something of a bad press: said to be expensive, to warp, rot, and need plenty of maintenance. Apparently though, modern manufacturing methods mean that none of this is necessarily true.

Some people in the trade have been working to get this message across, Naomi Cleaver (one of the judges of the Sterling Prize – a well know architecture competition) has put her name to www.woodwindowalliance.com in an attempt remind people they don’t have to select plastic and that there are affordable windows available in the UK.

A quick read of other websites such as www.woodforgood.com also highlights that its not just recyclability that makes wood an inspired choice for those that care about the planet, Wood absorbs Carbon dioxide (CO2) rather than increasing emissions. Managed felling and replanting increases this effect, since young, growing trees absorb more CO2 than older, mature trees. Forests, and the wood they provide, are vital in the fight against climate change…

Unlike steel, cement, bricks or PVCu windows, wood requires less energy to convert it into usable form. A plastic window frame has more than seven times the energy input in manufacture of a wooden frame of similar size and design. By using timber products instead of PVCu the world will save around 0.5 tonnes of CO2 or every ten windows and up to four tonnes if used instead of aluminium.

A recent WWF report concludes timber windows are better for the environment than PVC windows. WWF is encouraging specifiers and buyers of windows to choose wood which has been certified by the Forest Stewardship Council (FSC). This guarantees the wood has been sourced from a well-managed forest or other controlled wood source, and ensures that the timber is legal and not from a controversial source.

As with most renovations a critical element for Laura and I will be the bottom line cost. Good quality wooden windows from a major manufacturer apparently cost from £250/m² for standard windows to £600/m² for windows of the ‘Passivhaus’ standard. Solid timber windows from a local joiner might cost £200 to £500/m2 and PVCu £200 to £350/m².  Regarding U-values we need to do a bit more research to find out if there are distinct differences in performance between different frame materials (I expect it is more likely to be affected by the quality of the glazing units)

We have already found some potential wooden window suppliers via the Wood Window Alliance website, if you can think of any in addition to West Port and Boyland Joinery, please let us know via comments, also, if anybody has any counter arguments for Aluminium (which we had been considering specifying) please let us know.