What are Sash Windows: A Complete Guide

What are Sash Windows?

A sash window is a type of window consisting of two or more movable panels, or “sashes,” that slide vertically within a frame. These sashes typically hold glass panes and can be opened and closed to control airflow and light.

How Does Sash Window Work?

Sash windows work by using a simple yet effective mechanism that has been used for centuries. They consist of one or more movable panels, called sashes, which hold the glass panes in place. The sashes are typically set within a wooden or uPVC frame and can slide vertically (or sometimes horizontally) to open and close. The movement of the sashes is facilitated by a system of counterweights and pulleys or, in modern versions, by spring balances.

The counterweights, usually made of cast iron or lead, are connected to the sashes via cords or chains, ensuring that the window can be opened and held in place at any height without requiring manual support. This system not only makes sash windows easy to operate but also provides ventilation control by allowing the top and bottom sashes to be opened simultaneously, promoting airflow. Modern sash windows often include weatherproof seals and double glazing for improved insulation while retaining the traditional aesthetic. This timeless design combines functionality with elegance, making sash windows a popular choice in both historical and contemporary architecture.

What are the Benefits of Sash Windows?

The benefits of sash windows include ventilation, durability, security, energy efficiency, natural lighting and aesthetics.

Ventilation: One of the key benefits of sash windows is their excellent ventilation. You can open them from both the top and the bottom, allowing warm air to escape from the top and cool air to enter from the bottom. This creates a natural airflow that can effectively cool your home.  

Cleaning: Many modern sash windows have a “tilt-in” feature, which allows you to tilt the sashes inwards for easy cleaning from inside your home.

Aesthetics: Sash windows have a timeless elegance that can enhance the beauty of any home, especially traditional or period properties. They add character and charm, and can significantly improve your home’s curb appeal.

Natural Light: Sash windows typically have large glass panes that allow ample natural light to enter your home. This can brighten up your rooms and create a more welcoming atmosphere.

Energy Efficiency: While older single-glazed sash windows can be draughty, modern double or triple-glazed sash windows offer excellent insulation. They can help to reduce heat loss in winter and heat gain in summer, which can lead to lower energy bills and a more comfortable home.

Security: Modern sash windows can be fitted with security features such as multi-point locking systems and toughened glass to improve your home’s security.

Durability: Sash windows, especially those made from high-quality timber, can be very durable and long-lasting with proper maintenance.

How Long Do Sash Windows last?

Typically, the sash windows can last up to 20 –100 years. Here is a breakdown of the lifespan of sash windows for different materials.

Timber Sash Windows: With proper care and maintenance, timber sash windows can last for 100 years or even longer. There are many examples of historic buildings with original sash windows that are still in good condition after centuries of use. Some experts suggest a well-maintained timber window can last at least twice as long as a uPVC window.  

uPVC Sash Windows: uPVC windows typically have a lifespan of around 20-30 years.    

Aluminum Sash Windows: Aluminum windows are known for their durability and can last for 40-50 years or more.

Can Sash Windows have Double Glazing?

Yes, Sash windows can definitely have double glazing, and it’s a very common and beneficial upgrade. Here’s how it works and why it’s a good idea.

How Double-Glazing Works in Sash Windows:

Replacement Sashes: The most common method is to replace the existing single-glazed sashes with new sashes that are specifically designed to hold double-glazed units. These units consist of two panes of glass with a gap between them, usually filled with an inert gas like argon.

Slimline Double Glazing: Modern technology has allowed for the development of “slimline” double glazing units, which are thinner than traditional double glazing. This is particularly important for sash windows, as it helps to maintain the original appearance and proportions of the window.

Secondary Glazing: Another option, though less common for full upgrades, is secondary glazing. This involves adding a second window on the inside of the existing sash window. While it improves insulation, it’s not as effective as replacing the sashes with proper double glazing.

Can Sash Windows Be Noisy?

Yes, traditional sash windows can be noisy. Because older sash windows often have single-pane glass, which doesn’t provide good sound insulation. Over time, gaps can develop between the sashes and the frame, allowing sound to seep through. Strong winds can cause the sashes to rattle against the frame, creating noise.

What are sash windows frames made from?

Sash window frames are made from wood, uPVC, aluminum, or composite materials, each with specific properties.

Wood: Traditional sash windows are often made from hardwoods like oak or softwoods like pine. Hardwoods are more durable and can last over 50 years with proper maintenance. Softwoods are more affordable but may require more frequent upkeep. 

uPVC: Modern sash windows commonly use uPVC (unplasticized polyvinyl chloride) due to its durability, low maintenance, and affordability. uPVC frames can last 20-40 years and resist moisture and rot, making them a practical choice if you prefer minimal upkeep. 

Aluminum: Aluminum frames are strong, lightweight, and resistant to corrosion. They are ideal for modern designs and can last 30-50 years. Aluminum provides a slim profile, which allows for larger glass panes and better views. 

Composite: Composite sash windows combine materials like wood on the interior for insulation and aesthetic appeal, with aluminum or uPVC on the exterior for durability. This design offers a lifespan of around 40-60 years and reduces maintenance requirements. 

Can a sash window be opened from Outside?

Yes, a sash window be opened from outside, however sash windows are designed to open from the inside. Their construction makes opening them from the outside difficult and usually requires force, which can damage the window.

Here’s a breakdown:

Interlocking Design: The sashes (the movable parts of the window) overlap and interlock within the frame. This creates a tight seal against weather and provides security. This interlocking makes it hard to gain purchase from the outside to lift or slide the sashes. 

Weights and Pulleys/Springs: Traditional sash windows use a system of weights and pulleys concealed within the window frame to counterbalance the weight of the sashes. This allows for smooth operation from the inside. Modern sash windows often use springs for the same purpose. These mechanisms are not accessible from the outside, meaning you can’t manipulate them to open the window. 

Security Features: Many sash windows incorporate security features like sash locks or restrictors. These are designed to be engaged from the inside and further prevent opening from the outside.