How to reduce heat loss from old sash windows

Period windows are beautiful but weren’t originally designed with thermal efficiency in mind. Find out how to upgrade yours with these top tips from Ventrolla

a street of period red-brick Victorian homes with traditional windows
(Image credit: Ventrolla)

Windows play a huge role in maintaining the character of an older home. However original sash windows – which are often single glazed – can let your home down when it comes to thermal efficiency . This affects how comfortable your property is to live in, and can also impact on its resale value.

Fortunately, there are several ways to reduce the heat loss from your sash windows without losing their authentic look. Read on to find out how to improve thermal efficiency and continue to enjoy your home in the colder months.

1. Draught-proof your sash windows

Sash windows were a mainstay of Georgian and Victorian homes and many of us are still lucky enough to have them on our homes today. Also known as sliding sashes as the counterweighted windows slide over one another to open, their design can lead to their one drawback – poor airtightness which results in heat loss. 

On top of this, you may notice that if your sash windows are not draught-proofed they allow water ingress and rattle on windy days. Draught-proofing will solve these issues and while it can be done on a DIY basis, using a sash window expert will ensure you do not damage, affect the usability or change the external appearance of these windows. 

Casement windows can also be fitted with strips to prevent draughts, and don’t forget to draught-proof doors to for maximum thermal performance.

draughtproofing a sash window

The Ventrolla Perimeter Sealing System is suitable for both sash and casement windows and tested against 71mph winds. It is hidden in the frames and won’t impact on how the window opens. Upgrade your windows from just £500 per window

(Image credit: Ventrolla)

2. Fit secondary glazing

A lot of homes have single-glazed, original sash windows that are in a good state of repair. In these circumstances, replacement does not make sense, but the homeowner might still wish for levels of thermal performance and soundproofing that single glazing just can’t offer. 

This is where secondary glazing can make all the difference. It is fitted inside the existing windows and creates a void between the panes, which decreases the transfer of heat or sound  – much like double glazing would. Units start at around £350 per window so it is a budget-friendly option and also the best choice for Listed homes of those in Conservation Areas.

There are different types of secondary glazing depending on the type of windows and how often you use them. Lift-out units are great on windows that don’t need to be opened, but look for opening secondary glazing where ventilation is required. You then need to choose based on the type of window. For casement windows look for hinged units or horizontal sliders to allow access. And for sash windows opt for vertical sliders. The units are designed to match the original window, with meeting rails neatly hidden behind the existing framing. This means they can’t be seen from outside and won’t affect the look of your home. 

3. Install slim double-glazing units

In some cases, your single-glazed sash windows may be suitable for upgrade to double glazing. Slim double-glazing units can be retrofitted, allowing you to salvage much of the frame. This is the best way to get maximum thermal performance from your windows, without wasting perfectly good woodwork. Single glazing is often only half as thermally efficient as double glazing, so from just £1,000 per window you can vastly improve the comfort of your home and cut bills in the long term. In addition, the overall look of your windows will not be changed.

4. Replace the windows with thermally-efficient replicas

If none of the options above are suitable, or your current sash windows show signs of rot and need extensive repair, it will be best to consider replacement. When possible, you should look to replace like to like and this is why bespoke design from a heritage window specialist is essential. An expert joiner will be able to create authentic replacements that combine all the craftmanship of period designs, with modern glazing technology for a window that not only looks the part, but plays its part when it comes to energy efficiency too. 

Georgian house with new windows

Ventrolla can craft beautiful replacements for your period windows, starting from £1,500 per new window

(Image credit: Ventrolla)

Looking to improve your windows? Ventrolla complete over 18,600 sash window renovations a year and have over 30 years experience in upgrading and maintaining period windows in British homes. They pride themselves on being 21st century traditionalists, helping futureproof the country’s heritage housing stock for the next generation. Visit Ventrolla for a free window survey or call 0808 301 9647.

Real Homes is committed to sharing the best advice on everything from renovating your home to what products to fill it with. From DIY how tos, to ideas galleries and reviews Real Homes offers knowledge and expertise to help you do what you need to do, in a way that hopefully makes the process fun and easy. Our sponsored content is not an editorial endorsement, but allows you to connect with brands to assist your home renovation journey and alerts you to products you may not have known about before.