Sash Window Draught-Proofing for an Energy-Efficient Home

draught proofing windows

Sash window draught-proofing is a simple yet effective way to reduce energy costs and still keep your home warm. Common in Georgian and Victorian homes, these windows comprise movable panels or sashes, which form frames holding glass panes.

Over time, ageing sash windows may rattle and develop cracks, allowing cold air to enter and causing heat loss. This issue, known as draught, can affect home heating efficiency.

Unmanaged draughts can lead to a 50% loss in heating and cooling energy, costing you a fortune on heating bills.

This guide will cover effective draught-proofing techniques, various draught excluders, and their benefits, and provide tips on maintaining your draught-proofed sash windows for optimal performance.

How Does Draught-proofing Work?

Unlike casement windows that seal against the window frame, sliding sash windows must maintain a small gap between the sash perimeter and the frame to open and close. A traditional sash window has an airspace equivalent to a 6-inch square hole in the wall. The design feature allows for air movement, leading to draughts.

The goal of draught-proofing is to locate and seal openings that let in cold air during winter and allow warm air from your heating system to escape. This process boosts your home’s energy efficiency and overall comfort.

Draught-proofing sash windows is a bit more complex than insulating other types of windows because of their unique sliding mechanism. This design wears out window seals faster, making it important to select durable materials for long-lasting and effective draught sealing. You can use a range of materials as draught seals for sash windows, including:

  • Silicone Sealant – Provides a flexible and waterproof seal and can fill smaller gaps.
  • Metal or Plastic Brush Strips – Durable for sliding window parts, allows movement while preventing draughts.
  • Self-Adhesive Weather strips – Inexpensive, easy to install, and ideal for single-glazing.
  • Self-Adhesive Brush Seal Weather strips – Durable, conforms to surfaces, allows movement, suitable for sliding parts, visible bristles, and high traffic resistance.
  • EPDM Rubber Strips – EPDM stands for Ethylene Propylene Diene Monomer. It is durable and suitable for glazed sash windows, can compress and spring back to shape, and is good for sealing gaps of varying sizes.
  • Secondary Glazing Kits – Provides excellent draught-proofing and also adds noise insulation and thermal efficiency.
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How to Draught-Proof Sash Windows

Draught-proofing sash windows yourself is an effective way to enhance your home’s energy efficiency and comfort. Follow this step-by-step guide for a DIY draught-proofing process for your sash windows.

  • Ensure that the window frames are clean and dry. Use a moist cloth to remove dirt and loose paint from your window frame.
  • Measure the lengths of the window frame where you will apply the draught-proofing strip. Cut the strips to these lengths.
  • Apply the Draught-Proofing Strips:
    • For self-adhesive strips Type D, peel off the backing and press the strip firmly into place along the frame where the window sashes meet the frame.
    • For draught-proof strips that require nailing, such as plastic strips and silicone sealant, position the strip and gently nail or tack it into place, being careful not to split the wood.
  • If there’s a gap between the sliding sashes, apply a brush strip or seal along this part.
  • Ensure the draught-proofing does not impede the window’s movement. Open and close the window several times to ensure it still operates smoothly.
  • Seal the Top and Bottom of the Window. Apply draught-proofing strips to the top and bottom of the window where the sashes slide to seal overlooked areas.
  • After a few days, check the strips to ensure they are still in place and provide a good seal. Adjust or replace any parts that have become loose or ineffective, ensuring your window shut tightly.

Keep in mind that although DIY draught-proofing is beneficial, it’s crucial to avoid sealing the window too tightly, which might hinder its ability to open or close smoothly.

Adequate ventilation is essential, particularly in a period property. If you’re unsure or uncomfortable performing these tasks, it’s advisable to seek help from a professional.

Benefits of Sash Window Draught-Proofing

Window draught-proofing systems offer several benefits beyond just preventing cold air from entering a room. Here are some of the key advantages:

  • Thermal Efficiency – By sealing the gap between sashes, draught-proofing reduces the amount of cold draught entering and warm air leaving a room, thus lowering the demand for heating systems and enhancing energy savings.
  • Reduced Energy Bills – By draught-proofing your windows, you can significantly reduce your heating costs, resulting in substantial financial savings.
  • Draught-proofing and weather stripping aid ventilation management by sealing gaps in window frames and between moving panels.
  • Implementing draught-proofing measures for your sash windows reduces noise pollution and eliminates window rattling.
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Budget for Sash Window Draught-Proofing

Sash window replacement isn’t necessary for effective draught-proofing. Professional draught-proofing typically costs between £250 and £400.

This cost variation depends on the draught seal you are draught-proofing with. For instance, self-adhesive weather strips are roughly £5-6 for a 5m roll, while 5m self-adhesive brush seal weather strips are as little as £3-4.

The cost of sash window draught-proofing also depends on the dimensions and the ease with which one can access the sash windows for installation. Types of windows could also be a factor. For example, in glazed windows, single-glazing is cheaper to draught-proof compared to double-glazing.

How to Maintain Your Sash Windows After draught-proofing

Keeping your window draught-proofing system in prime condition is a straightforward task that requires consistent care. The routine cleaning of sash window seals is key to ensuring their longevity and effectiveness. Use a gentle solution of warm, soapy water to cleanse these seals, which helps to keep them pliable and effective at blocking out cold draught and dust ingress.

It’s crucial to prevent the draught seals from accidentally getting coated with paint during decorating projects. Vigilance against such accidents will prevent the seals from becoming rigid and losing their insulating properties, ensuring that your sash windows remain functional.

It’s important to note that while draught-proofing is beneficial, it should be done with consideration for maintaining adequate ventilation, especially in areas where good air quality is essential, such as in kitchens and bathrooms.

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Nicole Sage

Nicole Sage is the founder of Sleek-chic Interiors and is a highly experienced interiors writer and skilled home renovator who has a passion for all things design. She has been featured as an authority at Pinterest, Ideal Home, Daily Mail and in countless other interviews. For 8 years, Nicole has written, observed key interior trends, renovated and undertaken interior short courses at the renown KLC school where she has gained her grounding interior design principles. With a keen eye for detail and a love of creativity, she shares her expertise on the latest interior trends, practical DIY tutorials, and styling inspiration to help others transform their homes into stunning spaces. With a commitment to delivering informative and engaging content, Nicole inspires and empowers readers to explore their own unique sense of style and create beautiful, personalised interiors. Contact her at for interiors advice, colour questions and any commentary.

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