Can You Put Double Glazing In Old Windows?

Compared to its more contemporary counterparts, the character and allure of older windows are frequently hard to match. There is plenty to admire in old windows, including the intricate woodwork, the distinctive shapes, and the historical importance. But energy efficiency is usually where these windows fall short.

Many homeowners are concerned about the visual impact and structural integrity of their homes when they consider upgrading their existing windows to double-glazing. This is because single-pane glass does not provide much insulation against temperature changes or noise.

The potential benefits of installing double glazing in older windows are explored in this article. We will go over the many options, go over the pros and drawbacks, and give homeowners some advice on things to think about when choosing an update. After reading this, you will have a better idea of whether or not double glazing your old windows is a good idea, and if so, how to get the greatest benefits.

Can You Put Double Glazing In Old Windows?

Yes, you can put double glazing in old windows, but the approach you take will depend on the condition of your existing windows, your budget, and the level of energy efficiency you’re aiming for. Here are some common methods to consider when upgrading old windows to double glazing, click here:

  • Secondary Glazing: This method involves installing a second pane of glass on the inside of your existing window frame. It creates an insulating air gap without altering the external appearance of the window. Secondary glazing is a popular choice for heritage buildings or where preserving the original windows is essential.
  • Window Inserts: Similar to secondary glazing, window inserts fit into the existing frame, creating a double-glazed effect. These are typically removable and can be a less intrusive solution compared to replacing the entire frame.
  • Double-Glazed Units (DGUs): This approach involves replacing the single-pane glass with double-glazed units. If the existing window frame is in good condition, this can be an effective way to improve energy efficiency without changing the overall look of the window. However, this may require modifications to the frame to accommodate the thicker glass units.
  • Full Window Replacement: In cases where the window frames are damaged or not suitable for retrofit, replacing the entire window with a new double-glazed unit may be the best solution. This option offers the most significant energy efficiency benefits but can alter the appearance of your home’s exterior.

Before proceeding with any double-glazing solution, consider the following factors:

  • Historic Preservation: If your home has historic or architectural significance, check with local preservation authorities before making alterations. Certain regulations may restrict the types of changes you can make to the windows.
  • Budget: Costs can vary depending on the method used. Secondary glazing and inserts are generally more affordable, while full window replacement can be more expensive.
  • Energy Efficiency Goals: Determine your desired level of energy efficiency and consider whether you need additional features like low-emissivity coatings or gas-filled panes.

The best approach to upgrading old windows with double glazing will depend on your specific needs and circumstances. By carefully weighing your options, you can find a solution that enhances energy efficiency while preserving the unique character of your home’s windows.

Can You Fit Double Glazing To Existing Sash Windows?

Yes, you can fit double glazing to existing sash windows, though it can be a more complex process than with other window types. Sash windows have a unique design and are often found in older or historic homes, which adds to the challenge of integrating modern double glazing without compromising the aesthetic or structural integrity. Here’s how it’s typically done:

  • Retrofitting Double-Glazed Units: This approach involves replacing the single-pane glass in the sash windows with double-glazed units (DGUs). To do this, the existing sash frame must be carefully altered to fit the thicker double-glazed glass. The frames may need to be strengthened or adjusted to ensure smooth operation after the upgrade. This method maintains the original look of the sash windows while significantly improving energy efficiency.
  • Secondary Glazing: An alternative to replacing the glass within the sash frame is adding secondary glazing. This involves installing a separate pane of glass on the inside of the window, creating an insulating air gap. Secondary glazing is a popular option for sash windows in heritage or conservation areas where altering the original windows might be restricted.
  • Replacement Sashes with Double Glazing: If the existing sash frames are in poor condition, a common solution is to replace the entire sash assembly with new sashes that are designed to accommodate double-glazed units. This can be done without changing the outer frame, thus preserving the look of the window from the exterior while benefiting from modern energy efficiency.
  • Full Window Replacement: In some cases, the existing sash window frames may be too deteriorated or unsuitable for retrofitting with double glazing. In these situations, replacing the entire window with a new double-glazed sash window may be the best course of action. This option offers the highest energy efficiency, but it is also the most intrusive and may require approval if your property has historical or architectural significance.

Factors To Consider

  • Historic Preservation: If your home is listed or in a conservation area, make sure to get the necessary permissions before making changes to the windows.
  • Budget: Retrofitting existing sash windows with double glazing can be more expensive than other window types due to the intricate design and craftsmanship involved.
  • Energy Efficiency Goals: Determine whether the level of energy efficiency offered by double glazing aligns with your goals, as well as whether additional weatherproofing is needed.
  • Professional Expertise: Given the complexity of sash windows, it’s crucial to work with experienced professionals who specialize in retrofitting or replacing sash windows.

By considering these factors and exploring the various methods for adding double glazing to existing sash windows, you can improve energy efficiency without sacrificing the unique character and charm of your home’s original windows.


Retrofitting existing sash windows with double glazing is a practical solution to improving energy efficiency while preserving the visual appeal of traditional window designs. This can be accomplished by installing double glazing. Nevertheless, the procedure can be lengthy and difficult, necessitating meticulous planning, skilled craftsmanship, and careful consideration of criteria for the preservation of ancient buildings.

There is a wide range of choices available, including retrofitting double-glazed units into pre-existing sash frames, installing secondary glazing, or replacing the complete sash assembly. Each strategy comes with its own individual set of advantages and disadvantages, and the decision-making process is heavily influenced by a variety of circumstances, including the available funds, the level of energy efficiency that is required, and the legislation that governs historic properties.

When it comes to sash window restoration and double glazing installation, it is essential to collaborate with seasoned professionals who have expertise in these disciplines. This ensures that the process is carried out with precision, so retaining the one-of-a-kind personality of your home while simultaneously getting the benefits of energy efficiency that you are looking for.

Additionally, if you own a historic home, you should make sure that you comply with the local legislation and receive the required approvals before making any modifications to the property.

You will be able to update your sash windows to double glazing with complete assurance if you carefully consider the various alternatives available to you and consider the wider influence on the personality of your home. The outcome is a living area that is not only comfortable but also energy-efficient, and it pays homage to the past while also embracing current technology.