Making Sash Windows Energy Efficient 


Sash windows are a classic fixture found on countless period properties and historic buildings. They look the part, with heritage in abundance, but are they energy efficient? In short, no. The vast majority of sash windows are single glazed, with the potential for poor sealing around the glazing and the wooden frame.

Read on to find out what you can do, and how to save yourself money in the long run.

Feeling a draught?

In many cases, sash windows have poor energy-efficiency because they let in a draught. Original wooden frames become damaged by wood decay or flaking, which leads to gaps in the structure. This, along with poor sealing around the window pane, allows cold air into the home and lets warm air out. It makes it much harder to heat your home.

The solution? Simple draught-proofing. Specialist window companies can add draught-proofing strips to your windows and repair the frames. It will reduce the draughtiness of your windows, keep heat in your home and make it much easier to maintain a comfortable temperature. It will also get rid of any annoying draughty whistles.

Tackling the bigger problem

Sometimes the problem isn’t down to draughts. Sash windows may simply have poor insulation because of their single glazing. Double glazing is the standard solution to this problem. But for sash windows, it’s not always possible. The thickness required for double glazing damages the original frames, meaning you’ll have to damage the heritage of your windows to improve their energy efficiency.

Fortunately, there are other ways. Firstly, shutters. These are wooden attachments on the inside of sash windows, which close shut to provide extra insulation. They were used in the past for exactly that reason, and are still attached to some sash windows. If your sash windows have these in place, it’s a good idea to use them. But you can also have new shutters installed. They’re both practical and attractive, adding to the classic heritage look.

Maintaining natural light

Unfortunately, there is a problem with shutters. In order to improve insulation, they have to be closed. That means less natural light entering your property. An alternative solution, suggested by Historic England, is secondary glazing. With secondary glazing, you add a second sheet of glass to the internal side of the window. The air gap in between this and the original window provides improved insulation without affecting the window’s appearance or obstructing any light. Job done!

High quality secondary glazing 

When you’re dealing with heritage and listed buildings, it’s essential to get the best renovations available. You want to maintain the quality, while ensuring your property is as energy efficient as possible.

Clearview are secondary glazing specialists, with over two decades of experience. Commercial, residential and heritage – we’ve done it all. Our high performance secondary glazing on sash windows can provide your home with the extra insulation it needs. Your energy bills will be shrunk, and you’ll save more money over time. It really is that simple. See how we can help you, using our online fast quote finder.

Discover How To Stop Draughts for Good And Save On Your Energy Bills

This free eGuide – written by specialists – explains in simple terms how to improve the thermal efficiency of your windows by more than 60% and how you can reduce your yearly heating bill by 15%.

Simply enter your name and email below and we will send a free copy straight to your inbox.


Clearview secondary glazing - the solution to significantly improved acoustic and heat insulation to your property, making your home or offices more comfortable, secure, greener and cost efficient to run. Achieved without the disruption of replacement windows, and without damaging the character of your building.

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