Sash windows lend a timeless elegance to a building’s facade. If you’re a lucky owner of a period home graced with these charming windows, you may grapple with an important decision: should you replace the glass when problems arise? While understandable, full window replacement isn’t always your only solution. We’ll explore the advantages of repairing or replacing sash window glass, helping you make the decision that best suits your home and budget.

Old Sash Windows

Factors to Consider Before Replacing Glass

Before committing to glass replacement for your old sash windows, there are several things to consider:

  • Age and condition of the glass: Is it original handblown glass or newer? Preserve original glass for its historical significance. If it’s cracked or severely damaged, replacing it might be necessary.
  • Window frame health: Thoroughly examine the wooden frame surrounding the glass. Severe rot, warpage, or structural concerns are red flags indicating the entire window may need replacing.
  • Energy efficiency: Old, single-pane glass is a major source of heat loss. Consider if replacing it with energy-efficient options makes financial sense long-term.
  • Budget: Glass replacement is usually less expensive than full window replacement. Get quotes for both before deciding.
  • Historical preservation: For buildings in conservation areas or possessing historical significance, regulations may stipulate window preservation, making repair your primary choice.

The Benefits of Glass Replacement in Old Sash Windows

Here are the main reasons to choose glass replacement:

  • Safety: Damaged glass poses a safety hazard. Glass replacement is essential to maintaining a safe environment, especially when there are children around.
  • Improved Function: Broken sashes, sticking windows, and missing panes make it hard for a window to perform correctly. Glass replacement can help restore proper opening and closing.
  • Energy Savings: Upgrading to double-glazed glass with modern sealants can significantly reduce drafts and heat loss, leading to lower energy bills.
  • Noise reduction: Double glazing can act as an added barrier against external noise, promoting a more peaceful indoor environment.
  • Resale Value: If you intend to sell soon, newer glass and window components can increase the overall value of your property.

When Full Sash Window Replacement is Necessary

In some cases, full sash window replacement becomes inevitable. Here are some scenarios where this might be the best option:

  • Extensive damage: If the timber frame has severe rot, warping, or damage beyond repair, you must replace the window to restore its integrity.
  • Poor energy efficiency: Old sash windows can be drafty and lead to heat loss. If you want significantly improved energy efficiency, modern sash windows – often with double glazing – offer superior thermal performance.
  • Severe degradation: If the glass severely warps or clouds, replacing the entire sash lets you upgrade the window while keeping its visual appeal.

DIY or Professional Glass Replacement: Which to Choose?

This depends greatly on the extent of the damage and your personal skill level:

  • Minor repairs: DIY kits for small cracks and chips do exist. If you feel comfortable tackling these repairs, it can be cost-effective.
  • Major repairs or full pane replacement: Unless you have significant glazing or carpentry experience, it’s advisable to consult a professional. A professional will use the right tools and knowledge to safely complete the job while preserving the window’s character.

Finding a Qualified Glazier or Sash Window Specialist

If you decide professional help is needed, invest time in choosing the right one for the job:

  • Specialisation: Look for professionals who specialise in sash window repair/restoration. They’ll have deep knowledge of traditional techniques and materials.
  • Experience: Ask about their experience working with older homes and the specific types of windows you have.
  • References: Ask for references from previous clients and, if possible, look at examples of their work in person.
  • Insurance: Ensure anyone working on your home has adequate insurance coverage for their workers and protection in case of any accidental damage.


Can I replace the glass myself? 

While possible, it requires skill and specific tools. If you’re not familiar with glazing techniques, hiring a professional is recommended.

How much does it cost? 

Costs depend on the size of the window, type of glass, and labor charges in your area.

Can I upgrade to double glazing? 

In some instances, existing sashes can be adapted for slim-profile double

Deciding whether to replace or repair glass in old sash windows is rarely a straightforward answer. The best option depends on individual circumstances, the specific conditions of your windows, and your priorities. Factors like historical preservation, budget, and energy efficiency should all factor into your final decision. By carefully weighing the considerations we’ve outlined and seeking expert advice if needed, you can make an informed choice to keep those beautiful sash windows working and looking their best for years to come.