Changeworks Report

Back in January we posted a News Item mentioning that Histoglass had been invited to take part in the Lauriston Place Trial in Edinburgh, carried out by Changeworks on behalf of Historic Scotland and Edinburgh Council.

Now, 10 months later, after the units have been installed and tested, Changeworks have published the report.
Even though we are very pleased to read that Changeworks have made a recommendation to Edinburgh Council that  ‘Slim-profile double glazing should be permitted in listed buildings, where the original glazing is no longer in place....’ we would like to have seen it taken it a couple of steps further and would make the following recommendations for future trial works:

1. Being ‘green’ only works when the life-span of materials provided is long. There is little point in trying to be green when no allowance is made for the durability of products. This can easily be achieved by making sure all products are vetted and that all included (gas-filled) systems actually meet all 6 parts of BS EN 1279. This is the British and European standard to which all gas-filled (thin) double glazing needs to be manufactured. In addition to being a legal requirement this is also a guarantee of both quality and longevity. BS EN 1279 part 3 is a long term test, and for a system to pass this it has to lose less than 1% of its insulating gas per year. This is not achievable with narrow warm edge spacers. No warranty changes this. For more information on this topic, please see the PDF BS EN 1279 Explained on http://www.histoglass.co.uk/technical.aspx.
2. Testing of different products with similar specifications should be carried out only in similar situations. The performance of the cellar windows is clearly not as good as the windows higher up in the building where there is more sunlight and more heat inside the property (as hot air rises).
3. Surprisingly, little is mentioned about the aesthetics of glass types used. In the opening statement, it is pointed out that ‘It is recognised that original glazing is deemed important in terms of conservation of historic materials, however in many cases this has been lost, representing an opportunity for thermal improvement without compromising historic fabric...’. It seems a shame then, that consequently the use of standard float glass and other anachronistic features in double-glazed units are accepted for replacements. It is widely accepted by English Heritage, The National Trust and Local Councils nationwide that the use of historic glass is one of the biggest contributors to the character of old buildings.
4. In old properties, shaped panes are very often present, which is something which can, as yet, not be done with vacuum units. Nor is the inclusion of toughened or laminated safety glass possible.
5. The spacer bars should not only be available in black or white, but in a wide variety of colours to match the colour of the paint work of the frames.
6. We applaud Edinburgh Council and Historic Scotland for taking the (brave) step to investigate the options and possibilities for sensitive double glazing in period and listed properties. For too long now, councils and organisations have stubbornly refused to embrace new technologies which make the reduction of carbon emissions of old buildings a realistic option, without altering the overall look and fabric of these valued buildings. However, a long-term rather than short to medium term approach would ensure that windows stand the test of time. If replacement of failing units has to be carried out within 5-6 years of installation, (with additional manufacturing, transportation, etc) all good intentions of saving energy will have been completely undone.

The full report can be found on http://www.changeworks.org.uk/projects/energy-heritage/544/