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How to Insulate Old Windows Without Replacing Them

Graeme Clarke February 06, 2018 Window Insulation

For owners of an older home – and the beautiful older wooden windows that come with it – the idea of replacing your older windows with new ones is far from appealing, even though you want the energy efficient advantages. 


A lot of property owners want to know how to insulate old windows without replacing them so they can retain the original character and operation of the windows they already have.


After all, who wants to give up the classic appeal of double hung sash windows and force a modern, but not so elegant, aluminium or PVC window into a lovely Victorian or Edwardian home?


You don’t have to. You can insulate old double-hung windows and wooden windows in general, without:


  • Tearing out your existing joinery;


  • Possibly damaging the surrounding wall cladding;


  • Losing the charming aesthetic and movement of your sash windows; and


  • Spending a lot of money on a new window replacement.


This is entirely possible when you use an advanced double glazing system like Thermawood’s patented dry retrofit double glazing system.


And, you’ll enjoy significant energy savings – plus other benefits – in the very cost effective process. 


This isn’t a cheap fix or DIY adjustment that doesn’t interfere with the look or function of your windows, like window pulley seals, plastic insulating film or secondary glazing. This is retrofit double glazing with proper sealed double glazed units, the solution that brings old windows into the 21st century – without sacrificing a thing. So let's look at how to make windows more energy efficient without replacing them.





How Retrofitting for Insulating Old Windows Works


Retrofitting is a window conversion rather than a replacement. Thermawood leaves the old timber joinery in place, converts it with special tooling by removing the glass and a small portion of the timber frame. Replacing the old single glaze with double glazing, also known as an insulated glass unit or IGU.


This IGU will make your home more energy efficient by transforming your windows from the source of one-third (or more) of your home’s heat loss, to one of your property’s best insulating assets from heat loss and heat gain. 


By using special types of glass such as low-E glass for greater thermal insulation or laminated glass for acoustic performance, you can get even better results, making you wonder how you ever managed to cope before the quiet and comfort that your new retrofitted windows provide.


Thermawood uses a unique patented process that makes it particularly useful for insulating and sealing house windows in older homes. This is because the system accounts for issues like:


  • Moisture and mould growth by using a complete drainage system under the double glazing;


  • Drafts by machining in special thermal and acoustic seals; and


  • The complex movement of sash windows by re-weighting the sash during the retrofit process.


Here’s how the Thermawood process works:


First, the single glazing is removed. This is where retrofit double glazing differs from new double glazing – the old glass comes out, but the existing timber joinery remains in place.



Then, a small part of the external window frame is removed to leave a 15-degree slope on the bottom of the frame. This slope allows for the installation of the grand adaptor, a unique and patented drainage system design made especially for Thermawood’s retrofit system, which is made from 100% recycled materials.



Next, a specialised two-compound backing seal is fixed to the frame and blocks are positioned on the grand adaptor’s locating steps. These are used to support the insulating glass unit. Then the double glazing unit is placed in the window, followed by the attachment of a front seal.



And finally, window beading is secured to the frame. The bottom bead is specially designed to let moisture escape, preventing any moisture build up around your IGU creating longevity in the double glazing and piece of mind that it will last a long time.




The Benefits Go Far Beyond Window Insulation


The extensive benefits of this advanced process lie in the intention of the system. Simply making your windows better is not the goal. With Thermawood, the objective is to create the best possible experience for homeowners, and for society in general, by using a system that is as efficient, effective and long-lasting as possible – without having to throw away all the good things about your windows. 


In addition to better thermal insulation, which means lower energy bills and a more comfortable home all year round, your retrofitted windows can offer:


  • Noise reduction – insulating against outdoor sounds results in a quieter home and a reduction in aaaall the stress-related, hearing and cardiovascular health issues that can creep up over years of aaachronic exposure to modern noise pollution.


  • Healthier home – with a dry system, your home will be less susceptible to mould growth, aaaoffering better air quality and an overall healthier living space.


  • Lower expense – retrofit double glazing, as opposed to replacing your older windows with new aaadouble glazing, is much more affordable. Retrofitting costs about one-third the price of double aaaglazing.


  • Faster process – you’ll experience less downtime. Because retrofitting is such a seamless aaaprocess, all the work can be done on site, and your windows won’t be left unfinished overnight aaa– anything that is taken out is completed on the same day.


  • Gorgeous windows – you’ll retain the charm and character of your older windows, as well as the aaaoriginal design and function.



Insulate Old Windows Without Replacing the Structure, or the Character


Updating your windows so you can enjoy a better insulated, more comfortable home doesn’t mean you have to give up the windows you love, or, in some cases, lose your heritage designation.


In fact, any period homeowner who has used the latest window technology to insulate their windows will probably warn you against a replacement. Here are just a few comments from some of Thermawood’s recent customers: 


“We recently had double glazing to retrofit some windows in our Edwardian house. The job was done professionally and the final result, exceptional.”


Double glazing for arch double hung windows in a heritage home, a customer noted:


“…The concern for preventing damage inside and outside the premises was meticulous and impressive…Living the result, I can strongly say, of being very delighted with the performance… to both noise and internal insulation qualities.”


And another commented:


My new Thermawood windows in my heritage house are terrific and have made my house much more comfortable thermally and acoustically. The double glazed units fit discretely in the window frames without impacting the heritage look. The old window mechanisms have been updated, and all work well now… was highly impressed and recommend them confidently.”


Even if you have very old wooden windows or believe upgrading your windows would be too complex because you have a special type of window, with advanced retrofit double glazing, you can enjoy all the benefits without sacrificing aesthetics, operation, or your budget. 


Today Thermawood’s window technology makes window insulation possible – no window replacements, no waste and no losing the beauty, integrity, and charm of your old wooden windows.




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