Improving Comfort and Cutting Energy Bills with Draught Proofing Old Sash Windows

nathan colwell
3 days ago
3 min read

Sash window draught proofing sewrvice - London

Old sash windows add charm and character to many homes, but they often come with a downside: they can let in cold air and cause heat loss. This leads to uncomfortable drafts and higher energy bills. Draught proofing these windows offers a practical way to improve comfort and reduce heating costs without replacing the entire window. This post explains how draught proofing works, its benefits, and how to do it effectively.

Why Old Sash Windows Are Prone to Draughts

Sash windows consist of two sliding panels, or sashes, that move vertically. Over time, the timber frames can shrink, warp, or become damaged. The gaps between the sashes and the frame allow cold air to enter and warm air to escape. Unlike modern double-glazed windows, many old sash windows have single panes and lack effective seals.

Common causes of draughts in sash windows include:

Worn or missing putty and glazing beads around the glass panes
Gaps between the sashes and the frame due to wood shrinkage
Loose or damaged cords and weights that affect sash alignment
Cracks or gaps in the window frame

These issues create cold spots and drafts that make rooms feel chilly, even when the heating is on.

How Draught Proofing Works

Draught proofing involves sealing the gaps around the window sashes to stop unwanted airflow. This can be done using flexible weatherstripping materials that compress when the window is closed, creating a tight seal without preventing the sash from sliding.

Common draught proofing materials for sash windows include:

Brush seals: Strips with fine bristles that block air but allow smooth movement
Foam or rubber strips: Compressible strips that fill gaps and reduce noise
Magnetic or silicone seals: Provide airtight closure with durability

The goal is to reduce air leakage while preserving the window’s original function and appearance. Properly installed draught proofing can cut heat loss by up to 50% in some cases.

Benefits of Draught Proofing Old Sash Windows

Improved Comfort

Sealing gaps stops cold air from entering and warm air from escaping. This means rooms stay warmer and more comfortable during colder months. Draught proofing also reduces cold spots near windows, making sitting by the window more pleasant.

Lower Energy Bills

Heating systems work harder when warm air escapes through gaps. Draught proofing reduces heat loss, so your heating system uses less energy to maintain a comfortable temperature. This can lead to noticeable savings on energy bills, especially in older homes with many sash windows.

Noise Reduction

The seals also help block outside noise, making interiors quieter. This is especially beneficial for homes near busy roads or noisy neighborhoods.

Preserving Character and Value

Draught proofing keeps the original sash windows intact, preserving the historic character of the home. It is a cost-effective alternative to full window replacement, which can be expensive and may alter the building’s appearance.

How to Draught Proof Old Sash Windows

Step 1: Inspect the Windows

Check for obvious gaps, damaged putty, or loose sashes. Identify where air leaks occur by feeling for drafts or using a smoke pencil or incense stick near the edges.

Step 2: Choose the Right Materials

Select weatherstripping designed for sash windows. Brush seals are popular because they allow the sashes to slide smoothly. Foam strips work well for larger gaps but may compress over time.

Step 3: Prepare the Surface

Clean the window frames thoroughly to remove dust, dirt, and old paint. This ensures good adhesion for the weatherstripping.

Step 4: Install the Weatherstripping

Measure and cut the strips to fit the top, bottom, and sides of the sashes. Attach them carefully according to the manufacturer’s instructions. Make sure the sashes still move freely after installation.

Step 5: Repair or Replace Putty

If glazing putty is cracked or missing, remove the old putty and apply fresh glazing compound. This seals the glass panes and prevents drafts.

Step 6: Maintain the Windows

Regularly check the seals and putty for wear and replace as needed. Keep the sashes clean and lubricated to ensure smooth operation.

Real-Life Example

A homeowner in a Victorian terrace noticed cold drafts around their sash windows and high heating bills during winter. After installing brush seals and renewing glazing putty on all windows, they reported a warmer home and a 20% reduction in heating costs over the next three months. The windows still looked original, and the seals did not interfere with opening or closing.