<img height="1" width="1" style="display:none" src="https://www.facebook.com/tr?id=598492074343094&amp;ev=PageView&amp;noscript=1">

How To Double Glaze Victorian Windows So They Last Another 100 Years

Graeme Clarke March 27, 2018 Heritage Windows

You know those beautiful old Victorian windows that are one of your home’s best features – the ones you wish could last another 100 years as they are, but you’re not sure you can deal with another winter of cold drafts and high energy bills? 


What if you could preserve them for another century?


And have them double glazed?

What a lot of heritage homeowners don’t realise is that you can restore Victorian era windows to their former glory – aesthetically and operationally. You can also have them converted to energy efficient double glazed windows. And you can keep your home’s heritage status.   


There’s even more good news.


You can do all of this for a fraction of the cost of replacing your windows with new double glazed windows.


With retrofit double glazing, performed by window professionals who have experience with heritage windows, you can tick all the boxes of your window wish list. Thermawood goes even further and will also take the time and effort to restore every component of your Victorian style windows or other type of heritage windows, including the hardware, your treasured leaded lights, or the original hardwood.




Before having your windows ripped out, messing with the cladding, trying to fit a ‘modern’ look into your classic period home aesthetic and losing all that makes your windows – and your home – so special, take the time to learn about what’s possible today with advanced window technology.


All Thermawood franchisees have the skill, experience – and respect for the traditional quality of heritage windows – that is necessary to upgrade them for 21st century issues. 




  • Insulation, 
  • Reduced noise, 
  • Improved air quality, 
  • And even enhanced security


Take care of all the issues you want solved with your century-old windows, without losing the irreplaceable value that the heritage look, distinction, and function offer.


Here’s how a considered approach to retrofit double glazing Victorian windows can give you everything you want from your windows without sacrificing what matters.



Retaining Your Victorian Era Wooden Joinery When Retrofit Double Glazing


Your existing timber may be more valuable than you realise.


A lot of the reason your windows have already lasted for this long is, windows that were made a century or more ago were often constructed with old growth timber. This wood offers incredible longevity. Even if your wooden windows have a couple nicks or scratches, they are still likely in good condition. This is remarkable when you consider the relatively short-lifespan of the products made today.


When it comes to windows, it’s true that they don’t make things like they used to.


This old growth timber is highly prized, not just because it can stand up to the test of time better than the materials used to make new windows today, but because it no longer exists.


The world has already used up the supply of old growth hardwood. 


That’s right. Your Victorian windows are in great condition after a century of use because they are likely made from materials that don’t exist anymore, at least not outside of the reclaimed wood market.


Why would you give up something like that when you don’t have to?


You can hold onto your prized original hardwood with retrofitting. 


Here’s how.


With the Thermawood process, a small piece of the existing timber hardwood is removed with special tooling. Rather than having a square rebate in the window this creates a 15 degree slope to:


  • Install the grand adaptor and dry glazing drainage system, followed by the insulating glass unit, aaaor IGU
  • Ensure maximum water drainage to prevent moisture build-up, mould growth and damage when aaathe final piece – the window beading – is secured to the frame




You see the issue with most wooden windows is that the glass is sitting in a square rebate with no drainage. This is where moisture builds up and begins rotting the window frame. This goes for incorrectly installed double glazing as well as the seals begin to fail and fogging in between the two panes of glass starts to occur.


This means, your wooden windows will be able to last another lifetime, or two. You’re using a timeless hardwood, and at the same time, adjusting the frame just enough to protect your gorgeous timber joinery from its greatest enemy – moisture and rot.


You get to keep the original structure and aesthetic of your windows and if there are any areas of the wooden frame that need to be refurbished, we’ll take the time to do that before installing the IGU.  


They won’t end up having that unattractive look when a modern frame is paired with other elements that are still heritage, like your: 


  • Victorian-styled leaded lights, 
  • Distinctive Colonial bars, 
  • Or the overall traditional feel of your double hung heritage windows.


The reality is, even with a coat of paint and a perfect installation job, new joinery is never going to look like the original. That smooth, polished, modern look, paired next to the unmistakable quality of genuine heritage pieces – it doesn’t look right.


The other major advantage of maintaining your existing wooden joinery is you know the frame will fit well. By cutting out your window and replacing it with a new frame or new sash, there’s a risk that you won’t have a flawless fit. Even if your new window is installed and it appears to fit and function perfectly, once things settle, you can get a certain degree of movement, making the forced fit work even less well.


If you want your Victorian windows to last, you’re going to see more longevity if you never remove the joinery in the first place and risk dealing with shifting pieces and an imperfect installation.



Preserving the Heritage Glass When Double Glazing


During the retrofit process, one of the first steps is to remove the existing glass pane. With double glazing for Victorian era windows, Thermawood professionals will carefully cut around the single glaze so it can be removed, fully intact.


So, if you have leadlights you’d like to preserve – which is what most owners of these decorative windows choose to do – you can rest assured, they’ll be able to last another 90 years plus once we have them taken care of and refitted into the double glazing.


Once the glass is completely removed without being damaged, we can send it to a professional leadlighter to be refurbished. Then, the restored piece is put inside the double glazing unit. As a result, you have a beautifully restored piece of period artistry, preserved safely within the double glazing indefinitely.


It’s this type of attention to detail, honouring the original quality of these older windows, which has led to Thermawood’s 100% approval track record by Heritage for Grade 1 and State-Listed properties.



Maintaining Your Heritage Window Hardware


When the goal is to make your double glazed Victorian windows look like they did when they were installed a century and a half ago – even though they have been retrofitted as high-performance windows – every feature matters. This includes your heritage hardware.


Often, because the windows are so old, one piece or another is at a point where it has seen better days. Or, it’s possible a different piece of hardware needs to be used to properly retrofit and refurbish the windows. For example, with double hung windows, sometimes the locks have to be replaced with slim-line locks.


To ensure a seamless heritage finish, at Thermawood, all franchises have a range of brass, satin chrome, and other materials commonly found in heritage hardware. This way, any piece that is replaced will match the existing hardware.


As long as the old hardware can still function properly, we’ll make sure to put it back in the window. As with your hardwood frame or sash, often the features that were made a century ago were crafted from better materials and can outlast the pieces that are factory made today.



The Endless Appeal of Victorian Style Double Glazed Windows


The subtle weathering of your double hung windows copper bars. The earthy warmth of the old growth timber joinery. The irreplaceable beauty of your lead lights.


Don’t throw it away because you want high performance windows.


You can upgrade your old Victorian windows for our era – and to thrive in your grandchildren’s era – without losing all the charm and character that makes heritage windows what they are.


Have them retrofitted by pros who understand the true value of real heritage windows, and get the best of both the past and the modern world.



See More of Our Posts

As the winter chill approaches, ensuring your home is well-prepared becomes
paramount. One key investment that stands out for its remarkable benefits during the colder months is double glazing.

As we face the challenges of rising energy costs and environmental concerns,
finding practical solutions to enhance the efficiency of our homes becomes
imperative. One such solution that stands out is double glazing. It is not merely a
modern trend but a smart investment in a more sustainable and cost-effective living space.