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The Best Way to Restore Heritage Sash Windows

Graeme Clarke April 03, 2018

Wondering if you can fully restore your sash window? 


Heritage property owners can experience all the benefits of a high performance window – energy efficiency, enhanced thermal insulation, noise reduction and a healthier, more comfortable home – without losing any of the qualities that make heritage sash windows so highly valued.


But, here’s the thing. 


There’s only one true way to accomplish upgraded and restored single hung and old double hung windows. And, only one company that offers a heritage-focused double glazing and restoration process – Thermawood.  


In fact...


Most people don’t even realise that sash window refurbishment is possible for heritage-listed properties.


Keep the charm, the classic movement and have an energy efficient double glazed window? No way.


If you ask many of the window companies out there today, this is what they’ll likely tell you. Not because they are being deceptive but rather because they genuinely can’t do a sash window renovation that will allow you to keep your heritage status and create all the benefits of high performance, double glazed windows.



Find out about the sensible solution for your old sash windows before wasting money on a subpar window product.


You don't want a product that may help insulate your gorgeous Victorian or Edwardian sash windows but ruin their look in the process. Or, one that may reduce drafts but you’re still left with a window that doesn’t function properly and does nothing about noise issues, let alone solving your summer window insulation dilemma. 


Worse yet, one that isn’t heritage approved, which means you risk persecution by the Heritage Council.



How Not to Restore Your Heritage Sash Windows


The primary threat to Australia’s heritage buildings and to their owners’ wallets is a lack of information. 


Because the system that is effective – Thermawood’s unique dry glazing system which is a patented retrofit double glazing system – is relatively new on the Australian market, many property owners and a lot of people working in the industry aren’t aware of what can be done.


As a result, other options for improving heritage sash windows are used. They often create more problems than they solve, especially in the long-run.


When you throw one of these impractical products on your lovely Victorian, Georgian or Edwardian sash windows, guess what happens?



You end up having to pay more money to have the work redone and your old period windows restored. 


Thermawood window professionals are often called out by customers to remove the products other companies have put in and then to complete the sash restoration and retrofit double glazing conversion.


This is what you should think twice about before investing your money:


Installing draft seals. Draft seals will help with insulation but that’s all they’ll do. And, unfortunately, you won’t notice a huge difference in your energy bills because you will still have to deal with the heat loss from having a single glazed window.


As part of the Thermawood process, we automatically machine draft seals directly into the window. This way, you get this benefit, plus everything else – lower energy bills, better acoustic performance, summer insulation, mould growth prevention and we’ll even fix your heritage double hung windows or single hung windows if they aren’t moving properly.


Secondary glazing. This is another option that can help. Before the Thermawood process was launched in Australia, councils would recommend either secondary glazing or insulating film to help with thermal insulation.


The problem is, you lose the aesthetic charm of your windows with secondary glazing. A lot of heritage owners end up not being happy with the results and opt for retrofit double glazing anyway.




A window film isn’t pretty either. More importantly, it won’t offer significant insulating benefits. Plastic window film also completely neglects noise pollution and condensation problems.


Using a double window. Different than double glazing, this is where a secondary window is put in. This method often ends up making the windows look different, not able to open and may not be heritage approved.



The Advanced Solution for Heritage Sash Window Restoration


With Thermawood’s unique Retrofit Double Glazing system, you’ll get optimal thermal and acoustic insulation, in addition to key benefits only Thermawood franchises offer. You get to keep the original charm and also prevent the cascading problems of moisture build-up around your windows – mould growth, compromised indoor air quality, and damaged or warped wooden frames or sashes due the the specially designed and patented drainage system incorporated within the system.


One of the major concerns for owners of old Victorian, Georgian and Edwardian sash windows – we’ll also make sure your windows operate like they did the day your home was originally finished. We’ll fix any problems with the joinery and replace broken hardware with new pieces that were made for heritage windows so that they operate like they are supposed to.




A process over 30 years in the making and the result of years of problem solving the issues that almost always occur from conventional double glazing and insulating window products, Thermawood Retrofit Double Glazing works like this:


  • Using special tooling, a small piece of the original timber frame is removed to create a 15-degree aaaangle, along with the old glass.
  • This angle allows us to put our new beading in at the same angle as your original sash window aaaused and install the patented dry glazing drainage system.
  • The double glazed unit is put into your existing window – which means you won’t even know aaayour heritage windows have been retrofitted by looking at them. There are no external add-ons. aaaEverything is seamlessly integrated into the windows and the sashes are reweighted.
  • The Patented Thermawood Drainage system is designed to provide longevity for the timber aaaframe and double glazing giving peace of mind that your double glazing and timber frames will aaalast for a long time.





As a result, your windows still look like they are straight out of the Edwardian or Victorian era, but they will keep your home comfortable, dry, and blissfully quiet, as any modern home in the 21st century should be.


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Whether you live in the subtropical regions of Australia or are simply trying to battle the intense summer sun in another part of the country, your single pane windows are both your property’s biggest insulation problem, and its solution.