What are the best ways to reduce heat loss in original sash windows?

By Sash Windows
Posted on:
Sash windows on Victorian semi detached property

Many old homes have original sash windows which, while undeniably charming, can be somewhat draughty. This can lead to considerable heat loss and make rooms feel cold and uncomfortable in the winter. At a time when energy costs are high, finding inventive ways to keep your home warm is essential.

The good news is that you don’t have to lose out on the character of your original windows. There are various cost-effective ways to improve energy efficiency and comfort. Read on to learn the best approaches to cut the draught and keep the charm of your period property’s original sash windows.

Invest in Professional Draught-Proofing

Old sash windows can last forever if properly maintained. But without care, they get draughty, sticky and let in water that rots the wood and materials. Preventing those headaches with regular upkeep and professional draught-proofing is crucial for preserving original windows.

When your antique windows need repair, hire a professional who knows historical restoration, not just a basic contractor. You want someone passionate about respecting heritage, who knows how to work with old materials the right way. Their specialised skills will protect the windows’ operation and historical look.

The right expert can replace damaged bits, refresh stuck sashes, seal draughts and make it all work like new. Prioritising quality professional care ensures your charming original windows will stay beautiful and functional for ages to come.

Add Weatherstripping

One of the easiest and most effective ways to reduce draughts in sash windows is to install weatherstripping. This adds a seal around the window sashes to close any gaps that let in cold air when the windows are shut.

There are a few options for weatherstripping original windows. Foam weatherstrip tape is inexpensive and easy to install and comes in a compressible form that inserts into the channels between sashes to block gaps and is available in various thicknesses.

Alternatively, rubber or vinyl weatherstripping can be pinned or glued into place, providing a tight seal and conforming well to irregular gaps. It’s important to take accurate measurements and assess gap widths to choose the right option for each window. The channels between sashes should also be carefully cleaned and prepared before installation.

Install Secondary Glazing

Installing secondary glazing is an excellent way to improve insulation and reduce cold air around original sash windows while retaining their aesthetic charm. Secondary glazing is a second layer of glazing behind the original window to create an insulating air gap. One option is DIY window film that shrinks tightly into place with heat. However, it prevents opening the windows until it’s removed which may not be practical.

More permanent secondary glazing uses sheets of polyester, acrylic or glass mounted in tracks inside the window reveal to maintain the original appearance. If the window depth allows, secondary glazing panes can be installed between the sash boxes, which hides the panes while keeping your windows functional.

For wider gaps, secondary glazing can be installed behind curtains or blinds to optimise insulation. Combined with weatherstripping and other draught-proofing measures, it helps retain the architectural charm of sash windows while creating a warmer, more energy efficient home.

Insulate Curtains and Shades

Adding insulating curtains or shades is an effective way to put an extra barrier between your windows and the cold outdoor air. Layered curtains made from a dense fabric like velvet or wool help prevent heat loss through windows. For the best insulation, hang curtains as close to the window as possible and extend them past the window edges to eliminate gaps.

Insulating cellular blinds are also excellent options for sash windows. These blinds have small air pockets built into the fabric, creating a thermal barrier, and they’re especially useful for single-pane windows since the “honeycomb” construction helps block the loss of warm indoor air.

Caulk Window Edges

Another simple technique for optimising energy efficiency is to seal around the edges with caulk. This fills any cracks and gaps where the window frames meet the walls, sills or mouldings, helping to prevent heat loss and cold air infiltration.

When choosing caulk for windows, look for a high-quality silicone, polyurethane or latex acrylic formula which offer long-lasting flexibility to maintain the seal and tolerate temperature changes. Carefully remove any old, cracked caulk and clean the areas to ensure the new caulk adheres properly. Caulking looks neat and prevents air leaks while keeping cold air out and hot air in.

Old sash windows are certainly charming, but their age-old design often makes them far less energy efficient than modern counterparts. However, as we’ve shown, there are several options available to upgrade and optimise the efficiency of original sash windows. For professional advice on draught-proofing your sash windows to improve the energy efficiency of your home, get in touch to arrange a free home survey.

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Helen Thomas
If I could clone you for all the other work we need to do over the next few years, I would! Thank you Mark for having such a good team in place. And huge thank you to Gary, Alex, John and Glen for taking such care of our windows and giving them what they needed after years (decades?) of neglect. Your attention to detail and 'doing it right' was very much appreciated, and your ability to solve problems was awesome. Helen & Tim, Godalming
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Amazing service from start to finish, no issues and no drama. The name Sash Window Experts is well chosen. Mark and his team - Gary and John were extremely helpful and professional and the end product - new sash sound proof double glaze windows upstairs and the kitchen triple sash window restored was top quality. I am very grateful to Sash Window Experts.
Amy Clarke
Cannot fault Mark and his team. We replaced the original sashes to our 1890's home with new like-for-like hardwood double glazed sash windows, and apart from being warmer, quieter, cleaner and altogether much smarter, you really wouldn't tell the difference - an amazing feat! They are absolutely beautiful windows, so well crafted and fitted, and the restoration of rot on the original box is imperceptible. Gary was friendly, clean, professional, and safe throughout the fitting, and very thoughtful in causing minimal disruption to the home. Absolutely thrilled with everything from the service to the price to the final finish. Delighted with them. Would recommend in a heartbeat.
Alison Fordham
We were nervous about getting our Victorian French windows restored and had received a ridiculously high quote. Sash Window Experts came in at a good price, gave a timeframe that worked with our schedule and did a great job. All as promised. The fitter, Gary, put the doors back in with great care and took time made sure they worked smoothly and also discussed any queries with us. Definitely made the job value for money. Very happy customers! We are looking forward to beign able to open our doors again and enjoy the garden. Thank you Mark and Co!
Peter Jones
Our house is Edwardian and has the original sash windows from 1906. I really want to make sure that any double glazed windows did not look out of place - so the woodwork, including the side bars etc should still be very thin to match the originals. I was fearing ending up with fat wooden bars but Mark took me to see a previous customer and I was happy to see the woodwork there and it put my mind at rest. We went for the thin Krypton windows. Now the windows are in they look very good and match very well. To be fair to everybody, we will not know until the winter how well they remedy our warmth and condensation issues in the house but are confident we made the right choice. Other suppliers would not do separate window panes and instead would only do a large window with a false wooden strip down the middle to make them look like two. We did not want that. The carpenters, Steve and Gary turned up on time (early actually) and got on with the job very efficiently and left no mess behind. I am very happy with the company and the windows.
Natasha Birley
Mark and his team are amazing. They restored our sash windows and doors. Mark is really knowledgeable and passionate and explained the process to me so I knew exactly what they would be doing. Once the work commenced I was amazed by how well they draft proofed the windows. They took so much care and the guys were polite, tidy, timely and a joy to have around. I would absolutely recommend the team to anyone thinking of restoring their windows, they look AMAZING!
Rachael Smith
Absolutely outstanding quality, value for money and service from Rob. This is the second time Rob has done work for us and we can highly recommend him. The sash windows are like new! Thanks Rob 😀
Jon Reed
Used these guys to do a total refurbishment on the windows of my 1870s Victorian Villa style house. Incredibly happy with the work and the guys doing it are just superb. On time to the minute every day, clearly take pride in the work they do and super friendly. Would not hesitate to use again!
Geoff Parsons
Excellent service from Mark. The windows installed last week. Look elegant and noise reduced considerably.
S Attewell
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