- •Contact us
- •About us
- •Advertise with the FT
- •Terms & conditions
© The Financial Times Ltd 2013 FT and 'Financial Times' are trademarks of The Financial Times Ltd.
March 23, 2012 9:31 pm
I’m filled with gloom. It is time for the once-a-decade redecoration of the windows on the street front of our house and we are about to kiss goodbye to the thick end of £10,000. We really have little choice; quite apart from the pressing need to keep the weather out, our house is protected by national legislation (in UK jargon our house is “listed”) and is also in a locally protected historic zone (a conservation area). Conservation area legislation restricts the type of alteration that can be made to houses in order to preserve the historic character of an area – this means repairing and repainting like-for-like. But across Europe and North America the windows of houses like ours have become a hotly contested issue.
According to the UK Government around 27 per cent of the country’s CO2 emissions are from fossil fuels burnt to provide energy for people’s homes, so tackling domestic energy efficiency is a high priority. Building new energy efficient houses will make little difference, at least in the medium term, because by 2050 only 30 per cent of the UK’s domestic housing stock will have been built since 2007. The only way out is to dramatically improve the energy efficiency of existing houses. This is not just a UK problem – it is a global issue. Retro-fitting hundreds of millions houses is an economic, political and cultural challenge for dozens of governments. It is a cultural challenge because although many newer buildings can be easily adapted without damaging their appearance and significance, older buildings in protected areas can be hugely diminished by ill-informed adaptation.
As governments and property owners focus on domestic energy efficiency, old windows are cast as the villain of the piece. Domestic energy assessments are required in the EU by the Energy Performance of Buildings Directive (2002) and they almost always unfairly discriminate against traditionally constructed buildings. Most assessments use a simplified and stripped-down box-ticking system that makes no allowance for the subtleties of traditional construction.
The most serious damage to the cultural value of historic areas, mostly town and village centres, is the installation of plastic windows (normally made from un-plasticised polyvinyl chloride or PVCu). Despite attempts at improving the design of these windows they are instantly recognisable because they cannot imitate historic mouldings, glazing bars and proportions. The UK English House Condition Survey undertaken in 2006 reported that more than 40 per cent of houses built between 1850 and 1899 now have PVCu double glazing; many of these are illegally installed in conservation areas.
Many owners think they are doing the right thing as they are convinced that their old windows cannot meet the UK target of a U value of 2 or less (the U value is a measure of heat loss through a sq m of a building). Unfortunately this is not true. Research undertaken by Danish and English national heritage agencies has recently demonstrated that traditional windows can perform just as well (and in some circumstances better) than plastic ones. My well-maintained windows of 1860, which have tight fitting shutters, have a U value of around 1.7 on a cold dark night. Simple maintenance, secondary glazing or even thick curtains can reduce heat loss by nearly 90 per cent. The fact is that properly maintained traditional windows can be efficient and effective for hundreds of years.
The fight back to reverse prejudice against traditional windows has begun, led by a number of northern European heritage agencies, particularly the UK, the Netherlands, Denmark and Sweden. Green governments in cold countries have a particular interest in the problem. Conservation bodies in other countries, including the US, are looking to their research to inform policy. Crucially, research has now shown that the energy savings generated by PVCu windows will never cover their capital cost because most have a life of less than 20 years. While these figures are sometimes disputed by manufacturers, the damage they do to the value of traditional buildings can’t be.
A survey of UK estate agents in 2009 showed they thought that replacement doors and windows, particularly PVCu units, were the biggest threat to property values in conservation areas. This is a big issue for owners because houses in these areas sell, in general, for more than houses elsewhere. Of the estate agents surveyed, 82 per cent agreed that original features added financial value to homes and 78 per cent thought that they helped houses sell more quickly.
Nobody suggests that the energy performance of old buildings should not be improved, only that the science used to measure their effectiveness is defective. By taking out your old wooden windows and replacing them with PVCu units made by carbon-hungry processes you are not only damaging the planet but your own pocket.
Dr Simon Thurley is the chief executive of English Heritage
Copyright The Financial Times Limited 2013. You may share using our article tools.
Please don't cut articles from FT.com and redistribute by email or post to the web.