10 Top Tips for Restoring Traditional Wooden Windows

Mukti Mitchell
Friday, 22nd April 2016

Sustainable Home Insulation expert, Mukti Mitchell, shares advice for restoring traditional windows during the warmer weather to bring peace of mind, reduce heating bills, save you money and lower your carbon footprint.

Almost everyone would love to live in a period home if they could afford the upkeep, and period properties require considerably more TLC to preserve their traditional elegance and character.  

Planning ahead for colder winter months by arranging for refurbishment in the summer can considerably reduce costs. And the satisfaction of knowing you’ve taken the care of your beautiful traditional windows in hand will greatly improve your peace of mind, especially since - by saving energy - you’re also be helping to protect the environment. 

Undertaking any restoration, decoration and putty work in the warm weather of summer is easier, quicker, more comfortable and less expensive than at any other time of year. And you also have the opportunity to install a conventional or advanced system of secondary glazing that will save heat otherwise lost through the windows in winter, making you much more warm and comfortable, saving energy and money, and insulating you against rising fuel costs.

1. Restore rather than replace. Look for craftspeople who can restore your window as this can often be done saving 90% of the original timber and glass, and will often outlast new windows.

2. When replacing timber, use reclaimed Pitch Pine for window timbers, which matches the weight, quality and durability of old timbers. 

3. For replacement sills, use sustainably grown European oak. Whereas the certification for hardwoods from tropical countries has recently been shown to be frequently illegitimate, European timber is far more traceable.

 4. The best gluing and filling compound is epoxy resin. From the marine industry, this is applied as a liquid resin so it adheres phenomenally well to the timbers. Filling compounds are then added to the resin that provide both volume and structural strength. Epoxy does not require a pressurised joint, which means that the absolute minimum amount of timber needs to be cut out and the end result is as strong and durable as the original window.

 5. Keep the original glass wherever possible. As well as the imperfections giving more character, old glass is whiter than green modern glass and therefore offers a better light-colour transmission spectrum. The use of epoxy resin facilitates retaining the original glass.

 6. When comparing the cost of restoration against new windows, ensure that you are including the cost of manufacturing the window, removing and disposing of the old window, fitting the new window/making good, as well as decorating and VAT.

 7. If your old windows are completely irreparable and you are going to replace them, always specify hardwood, because softwood windows can last as little as five years before beginning to decay.

 8. When replacing windows, always request the best possible double glazing, with 16mm void, and argon filled with a warm edge spacer bar, to offer the lowest possible u-value, ideally below 1.6. 

 9. Always get the lowest possible u-value. Single glazed windows have a u-value of 5.5, and triple glazing can be as low as 0.8, but an insulated wall can be 0.2. (A 'u-value' is the number of watts of heat transferred per square metre, per degree of temperature difference, from inside to outside).

 10. Historic England recommends that secondary glazing is preferable to double glazing for application to old windows. This is because old windows often have very fine glazing bars that cannot accommodate an efficient thickness of double glaze without seriously compromising the fabric and the look of the window. Furthermore, conservation double glazing (very slim units filled with an expensive gas called Krypton or Xenon) only comes with a guarantee, whereas secondary glazing can last 30 plus years.

Financially, insulating your period property is currently one of the highest-yielding investments available, offering up to 25% annual return with little risk, and saving tens of thousands of pounds over the next 20 years. And environmentally, insulating your home is one of one the most effective ways to reduce your carbon footprint, dramatically diminishing energy loss. Britain has 270 million windows, which if replaced every 25 years would mean throwing 10 million windows a year into landfill. So restoring old windows saves a massive impact on the countryside. And if all Britain’s old house stock was properly insulated, the nation’s national footprint would be cut by 10%.

Mukti Mitchell is the author of The Guide to Low Carbon Lifestyles, and director of Mitchell and Dickinson, a company specialising in comprehensive insulation and advanced secondary glazing systems for period properties: https://mitchellanddickinson.co.uk 0845 347 9367

To learn about secondary integrated glazing see:

Further resources

Planning to lay a new carpet? Save energy, insulate first

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