Last Updated on March 18, 2025

Single Glazed Sash Windows vs Double Glazed Sash Windows

When it comes to upgrading your home or property, one of the key improvements you can make is replacing old single-glazed sash windows with double glazing. However, homeowners and landlords in the UK often find themselves torn between the two options. 

With concerns about cost, energy efficiency, noise reduction, and overall aesthetics, the decision to replace single-glazed sash windows with double glazing isn’t always straightforward.

In this comprehensive guide, we’ll break down everything you need to know, from the benefits of each option to the costs involved, to help you make the right decision for your home or investment property.

Should I Replace Single Glazed Sash Windows With Double Glazing?

What are Single Glazed Sash Windows?

Single-glazed sash windows are traditional windows that consist of a single pane of glass held within a timber frame. Sash windows, which can slide vertically or horizontally, have long been a staple in UK homes, particularly in period properties. 

However, single glazing offers poor insulation and can result in heat loss, cold drafts, and higher energy bills.

What is a Double Glazed Sash Window?

Double glazing, on the other hand, consists of two panes of glass separated by a layer of air or gas. This additional layer acts as insulation, reducing heat loss and improving energy efficiency. 

Double glazing can be installed in a variety of window styles, including sash windows, and offers significant advantages over traditional single glazing.

Benefits of Double Glazing Sash Windows Over Single Glazing

1. Improved Energy Efficiency

Double glazing is known for its energy-saving properties. The layer of air or gas between the two panes of glass helps to insulate your home by preventing heat from escaping. This means that your home stays warmer in the winter and cooler in the summer, resulting in lower energy consumption and reduced heating costs.

For example:

• Single Glazing: Allows significant heat loss, requiring your heating system to work harder.
• Double Glazing: Helps retain heat within the home, reducing energy bills.

2. Noise Reduction

If you live in a busy area or near a noisy street, double glazing can significantly reduce the amount of noise entering your home. The extra layer of glass helps to block out external sounds, making your home quieter and more peaceful.

3. Condensation Prevention

Single-glazed windows are more prone to condensation, which can lead to mould growth and damage to your window frames and walls. Double glazing, on the other hand, reduces condensation, helping to keep your home dry and healthy.

4. Enhanced Security

Double-glazed windows are more secure than single-glazed windows. The added layer of glass makes it more difficult for intruders to break in, providing added peace of mind.

5. Increased Property Value

Replacing old, single-glazed sash windows with double glazing can increase the value of your property. Many homebuyers and renters now expect double-glazed windows, especially in older homes, as they provide improved comfort and efficiency.

Single Glazed Sash Window vs Double Glazed Sash Window Costs

One of the most significant factors in deciding whether to replace single-glazed sash windows with double glazing is the cost. Let’s compare the costs of installing and maintaining both options.

Cost of Single Glazed Sash Windows

• Initial Cost: Single-glazed sash windows are usually cheaper to install initially, with prices starting at around £150 to £250 per window (excluding installation).
• Energy Costs: Due to the poor insulation, you will likely spend more on heating bills, especially during the colder months.
• Maintenance Costs: Single-glazed windows often require more maintenance over time, including painting and sealing to prevent drafts and damage.

Cost of Double Glazing Sash Windows

• Initial Cost: Double-glazed sash windows typically cost between £400 to £600 per window, including installation.
• Energy Savings: Although the initial cost is higher, double glazing can save you money in the long run by reducing energy bills. In fact, homeowners can expect to save anywhere between £100 and £150 annually on energy bills.
• Maintenance Costs: Double-glazed windows require less maintenance than single glazing, and they typically come with warranties ranging from 10 to 20 years, depending on the manufacturer.

Pricing Table: Single Glazed vs Double Glazed Sash Windows

Read our guide to learn more about the cost of double glazing. 

Which Option Should You Choose?

1. Your Budget

If you have a tight budget and are looking for an immediate, low-cost solution, single glazing may seem appealing. However, keep in mind the long-term costs of higher energy bills and potential damage caused by condensation.

2. Energy Efficiency Needs

If you want to make your home more energy-efficient and save money in the long run, double glazing is the better option. It will help reduce heat loss, lower energy consumption, and improve comfort inside your home.

3. Property Type

If you live in a period property or a listed building, replacing single-glazed sash windows with double glazing can be more challenging. You may need to seek permission from your local council or heritage body before replacing traditional windows.

4. Environmental Impact

For environmentally conscious homeowners, double glazing offers a significant benefit by reducing your carbon footprint. With better insulation and lower energy consumption, your home will be more sustainable.

Are You Considering Upgrading Your Sash Windows?

If you’re considering upgrading your sash windows, it’s important to understand the different types of sash windows available. While traditional single-glazed sash windows offer a classic look, modern double-glazed options provide better insulation and durability. 

Depending on your home’s style and your energy efficiency needs, you might prefer one type over another.

One of the biggest factors in making your decision is cost. While single glazing is typically cheaper upfront, double glazing provides long-term savings through reduced energy bills. 

Before committing to double glazing, it’s worth evaluating whether a full window replacement is necessary or if sash replacement vs window replacement would be a better solution. In some cases, simply replacing the sash can improve insulation and aesthetics without the cost of a full window overhaul.

The overall cost of new windows depends on factors like material, window size, and installation fees. If you’re specifically looking for sash window pricing, our detailed guide on how much do sash windows cost breaks down price ranges based on different materials and styles, helping you budget more effectively.

Another crucial decision when upgrading your sash windows is choosing between uPVC sash windows and wooden sash windows. Considering the pros and cons of each material will help you make an informed choice.

Request a Free Quote for Double Glazed Sash Window Today!

Get in touch with us for a free, no-obligation quote to replace your windows with double glazing. Our expert team is here to help you make the right choice and ensure your home is both comfortable and energy-efficient.

FAQs

Can you fit double glazing to existing sash windows?

Yes, you can retrofit double glazing into existing sash windows, but it depends on the condition of the frames. If the original timber is in good shape, a specialist can install slimline double-glazed units while preserving the traditional aesthetic. 

Alternatively, you may need to replace the sashes or opt for complete new double-glazed sash windows for better energy efficiency and performance.

Do double glazed sash windows add value?

Yes, installing double-glazed sash windows can add value to your property. They improve energy efficiency, reduce noise, and enhance security while maintaining the period charm of your home. 

Many buyers appreciate the benefits of double glazing, especially in older properties where traditional aesthetics are important, making it a worthwhile investment.

Are double glazed sash windows more expensive?

Yes, double-glazed sash windows are generally more expensive than single-glazed ones due to the materials, manufacturing process, and installation requirements. 

However, they offer long-term savings through improved energy efficiency, lower heating costs, and increased property value. If you opt for bespoke timber double-glazed sash windows, the cost will be higher than standard uPVC options.

Conclusion

In conclusion, while replacing single-glazed sash windows with double glazing comes at a higher initial cost, it offers significant long-term benefits in terms of energy efficiency, comfort, security, and noise reduction. Not only will you save money on energy bills, but you’ll also increase the value of your property.