Sustainable Solutions for Old Windows

Plastic windows are often put into older buildings, to ‘upgrade’ old single glazed wooden windows. They can provide improvement in insulation via double-glazing and improved draft-proofing and so are often viewed as the sustainable solution. This is belied by their limited longevity, the PVC-U they are manufactured from gives them an expected maintenance free life of not much more than 30 years, at the end of which it is more likely that they are discarded and replaced than maintained.  There is a huge carbon footprint created in their manufacture and replacement and waste plastic is an increasing environmental problem.  

Old sash Windows don't have to be as beautiful

and rare as those on this Queen Anne townhouse

to be well worth preserving and restoring.

Listed historic buildings cannot be sympathetically re-fitted with modern plastic windows and the appearance of many otherwise handsome, unlisted buildings has been spoilt by the addition of carelessly chosen replacement windows. The making, rebuilding and repairing of sliding sash windows is now a reviving market which deserves encouragement

Wooden window frames and sashes of whatever age can be easily repaired if they have not been allowed to rot, though sliding sash windows in particular are often seen by the inexperienced as more trouble than they are worth to restore.  However weights, sash cords and other traditional sliding sash accessories are readily available from specialist suppliers and slender, pre-manufactured double glazing units can be used to replace original Victorian glass, which was often especially thick in larger windows. An expertly restored wooden sliding sash should be no harder to open and close than a UPVC replacement and will let in more light than a thicker framed plastic window, as is noted in the Building Regulations.

Marine Court, St Leonards, a 1930’s work of art made more

ordinary by the later, indiscriminate insertion of randomly

chosen windows and the infilling of balconies in the

apartments to the left. The sustainable solution here

is not obvious

UPVC can now be recycled and one major manufacturer of window profiles and other parts recycles up to 90% of old UPVC windows, including the glass, on their site in Derbyshire, though even this process has a carbon footprint in the energy used. The RecoVinyl Scheme is a European wide initiative to collect and recycle used  PVC building products to support the Vinyl 2010 Voluntary Commitment. The British Plastics Federation claims that, since inception of the scheme, the UK has led the way in the volume of PVC collected and recycled in Europe. The question is, how many discarded UPVC window actually do get recycled? Figures are lacking and it may be that too many still go to landfill and incinerators.

Northern European hardwood and slow grown softwood timber such as redwood are durable. If windows made from these are taken care of they will last for centuries, though requiring periodic maintenance involving paint and repair. Paint too has a carbon footprint, though modern non-volatile paints are improving all the time. PVC-U is comparatively low-maintenance but cannot be repaired as easily, so its longevity is not as good as properly maintained alternatives. Older PVC-U windows may suffer permanent discolouration and become brittle from exposure to sunlight. They can also become stained, mildew and bird droppings are reportedly particular problems and unlike timber they cannot be re-painted.

At ArchiFACT we have been carefully renovating and double glazing our existing 130 year old office windows.  The building is in a conservation area and we were advised that we would not be allowed to replace them with UPVC even if we wanted to as, due to local authority rules on multiple occupancy of buildings. It would have been easy, though expensive, to have new hardwood windows made. Having previous experience of repairing and restoring the original sliding sashes in an even older historic building, we were prepared for the task ahead, which proved fiddly but not over complicated.

Repairing a sash and painting old and new beads.

We contemplated using secondary internal glazing to increase the thermal insulation, but were able to devise a relatively simple system for inserting double glazing units into the existing large Victorian sashes, with modifications including additional beading for extra support and to increase the depth of the glazing pocket. The additional glass necessitated the adding of weights to the existing iron counterbalance. We were able to retain, with suitable repairs, all but one of the six original redwood sashes as well as the original weights, pulleys and smaller ironmongery except where these were missing. We replaced some beads and all the sash cords and added modern draft-proofing and security measures including laminate glass and opening restrictors. The windows now run smoothly, are thermally more effective and still let in the same light.

Early twentieth century steel windows, such as the original Crittalwindows at Marine Court, present a different set of problems. Manufactured prior to the introduction of rustproofing treatments at the end of the 1930’s these are usually side hung and also require additional maintenance. During wartime painting was often neglected and rust was allowed to set in often unseen beneath the putty in the glazing rebates. Cracked glass, provoked by compression from the building up of corrosion products, is a sure sign of underlying problems.

Steel windows are often worth conserving, particularly in buildings of special interest, and can usually be put back in good order. Careful removal of glass and putty, followed by grinding off rust to bright metal and the application of a good zinc based primer is essential, before re-glazing and painting. When extensive conservation work is needed, it may be worth having the windows taken out, stripped down and hot-dip galvanized before re-assembly. Alternatively, Crittal windows, if beyond practical repair, can still be replaced by their original manufacturer. Which of these approaches is adopted should not just rely on historical concerns or cost, today sustainability is arguably the most important factor.

To maximise its effect, sustainability needs to be factored in at all levels in the industry; any company or individual who is involved in the planning, design, build, supplying, conservation or maintenance of our built environment has a responsibility to not only be aware of sustainability, but be actively engaged. Clients who order a project, be it to replace a few windows in a small house or the re-fenestration of entire blocks, need to be aware that they also have a responsibility to make sustainable choices.

*

http://www.archifact.co.uk/

http://www.bpf.co.uk/enviromental_matters/The_Disposal_of_Old_PVCU_Windows.aspx

http://www.themodernhouse.com/sales-list/great-easton/

https://www.crittall-windows.co.uk/