How to Change Double Glazing Glass: Introduction
Double glazing is a staple in most UK homes, and learning how to change double glazing glass helps you reduce energy bills, keep warmth inside, and cut down on outside noise. However, even the best units don’t last forever. Over time, seals can fail, glass may crack, and that familiar misty look between panes often signals it’s time to replace double glazed window glass.
In this step-by-step guide, you’ll learn how to change double glazing glass safely and efficiently. We’ll cover what tools you’ll need, how to remove a damaged or blown double glazed unit, and the correct way to fit a new sealed glass unit. Many small jobs are manageable for confident DIYers, but for larger or higher windows, it’s usually best to call a professional glazing service.
Understanding double glazing glass replacement helps you spot issues early, make smarter decisions, and save money by knowing when a window glass replacement is enough instead of a full window upgrade.
Let’s dive in and get started.
Signs Your Double Glazing Needs Replacing
Spotting early signs of wear in your double glazing can save you money and prevent bigger issues later on. Knowing when to act is key to keeping your home warm, quiet, and energy-efficient. Below are the most common indicators that it’s time for a double glazing glass replacement.
1. Condensation Between the Panes
If you notice mist or condensation trapped between the panes, it’s a clear sign of a blown double glazing unit. When the seal fails, moisture seeps in, fogging your view and reducing your home’s insulation and efficiency.
2. Cracked or Broken Glass
Cracks, chips, or shattered panels are strong indicators that you need to replace double glazed window glass. Damaged glass not only looks unsightly but also compromises security and allows heat to escape, raising your energy bills.
3. Draughts or Leaks Around the Frame
Feeling a cold draught near your window? That often means the seal or beading around your uPVC or aluminium window has worn down. While resealing can be a short-term fix, persistent draughts usually point to a failed glazing unit that needs full replacement.
4. Cloudy or Milky Appearance
A cloudy or milky look inside the panes means the internal coating or moisture absorber (desiccant) has failed. Once this happens, the double glazing window glass loses both clarity and thermal performance.
5. Rattling or Movement in the Glass
If your glass rattles or shifts when touched, the packers or beading may have come loose. This weakens the window’s structure and can let in cold air or moisture.
Tip: You don’t always have to replace the full window. If the frame is still in good condition, a window glass replacement can restore warmth, soundproofing, and appearance at a much lower cost.
Tools and Materials You’ll Need
Before you start your double glazing glass replacement, make sure you’ve got all the right tools and safety gear ready. Working with glass takes precision and care, so having everything nearby helps the process go smoothly and safely.
Essential Tools
- Safety gloves and goggles – Always wear protection when handling or removing glass. Sharp edges and splinters are easy to overlook and can cause injury.
- Suction cups – These make lifting and positioning the double glazed window glass much safer and more controlled.
- Putty knife or flat screwdriver – Use this to gently remove the beading without scratching or damaging the uPVC or aluminium frame.
- Measuring tape – Accurate measurements are essential for ordering the right replacement double glazed unit.
- Glazing shovel or packers – These help keep the new glass level and secure inside the frame.
- Utility knife – Perfect for cutting away old silicone, sealant, or stubborn glazing tape.
Materials
- Replacement double glazed unit – Made to the same size and thickness as your existing one for a precise fit.
- Glazing tape or setting blocks – Used to cushion and secure the new glass, ensuring a snug and durable hold.
- Silicone sealant – Provides a strong, watertight finish and helps to block out draughts.
- Cleaning cloth and glass cleaner – Finish the job with a streak-free shine for a professional look.
Tip: If you’re unsure about measurements or fit, Colourglass Glazing offers made-to-measure double glazing units and friendly advice to help you get it right the first time.
Step-by-Step Guide to Changing Double Glazing Glass
Replacing a double glazed window glass unit might sound tricky, but with the right tools and a bit of patience, it’s a project that a confident DIYer can handle. Follow these double glazing glass replacement steps carefully to achieve a safe, tidy, and long-lasting result.
1. Measure Your Existing Unit
Getting your measurements right is essential for a perfect fit. Measure the width, height, and thickness of your current sealed unit from bead to bead — not the full frame. Always double-check your figures before ordering your replacement double glazed unit.
Tip: If you’re not sure, remove one of the glazing beads to confirm the glass thickness before placing your order.
2. Remove the Window Beading
Start with one of the longer vertical beads. Use a putty knife or flat screwdriver to gently ease it away from the frame. Take your time so you don’t damage the clips or scratch the uPVC or aluminium. Once one side is removed, work your way around the frame to remove the remaining beads.
Safety Note: Always support the glass while removing the final bead to stop it from slipping or falling out.
3. Take Out the Old Glass Unit
With the beads removed, use suction cups to carefully lift out the old double glazed glass unit. Clean the frame thoroughly by removing any old packers, dirt, or sealant. Then check the seals and drainage holes for wear before installing the new unit.
4. Fit the New Double Glazed Unit
Place new packers in the frame to keep the glass level and stable. Lower the new replacement glass unit into position using suction cups, ensuring it sits evenly. Once you’re happy with the alignment, refit the beads in reverse order — short sides last for a tight, secure fit.
Pro Tip: Tap the beads back in gently with your hand rather than a hammer to avoid damaging the frame or clips.
5. Seal and Finish
Apply a smooth bead of silicone sealant around the outer edge to create a watertight finish. Wipe away any excess, then clean and polish the glass for a professional result. Finally, check that the unit feels secure and free from draughts or gaps.
Need help? For larger windows, high installations, or a guaranteed professional finish, contact Colourglass Glazing. Our team specialises in window glass replacement and double glazing repairs, ensuring every job is done quickly, safely, and to a high standard.
When to Call a Professional for Double Glazing Glass Replacement
Even if you’re confident with tools, there are times when it’s smarter to call in the experts. Knowing when to hand a double glazing glass replacement job over can save you time, money, and a lot of frustration. Below are the key situations where a professional glazier is your best option.
1. Cracked or Damaged Frames
If your uPVC, aluminium, or timber window frame is cracked, warped, or loose, replacing the glass alone won’t fix the problem. A professional can inspect the frame, advise whether it needs repair or replacement, and ensure the new double glazed window glass fits perfectly.
2. Safety or Toughened Glass Installations
Toughened, laminated, and safety glass are heavier and more complex to handle. These window glass replacement jobs need the right tools, lifting equipment, and experience. Professional glaziers know how to manage the risks and make sure every unit is securely fitted.
3. Upper-Storey or Hard-to-Reach Windows
Working at height without proper safety gear can be dangerous. If your window is on an upper floor or awkward to reach, hire a trained and insured expert who can carry out the double glazing glass replacement safely and efficiently.
4. Heritage or Aluminium Windows
Older or specialist windows — like slimline aluminium or traditional timber — need extra care. A skilled glazier can fit a replacement double glazed unit that matches your property’s original style while improving performance.
5. Ongoing Condensation or Seal Failures
If your windows keep misting up or blowing seals, the issue may not be with the glass itself. A professional can check for poor drainage, failed seals, or incorrect installation, then fix the root cause to prevent further problems.
Need help? At Colourglass Glazing, we take care of everything from misted double glazing repairs to full window glass replacement across the Wirral and North West. Our experienced team supplies custom-made units and installs them quickly, cleanly, and safely — so your home stays warm, efficient, and secure.
FAQs on Double Glazing Glass Replacement
Unfortunately not. A double glazing glass replacement must be done as a full sealed unit. Double glazed windows are made from two panes sealed together with an insulating gap in between. Once that seal fails or a pane cracks, the entire replacement double glazed unit needs changing to restore energy efficiency and prevent condensation.
In the UK, the average window glass replacement costs between £60 and £150, depending on the type of glass, its size, and how accessible the window is. Toughened or oversized double glazed window glass will cost a bit more, but it’s still much cheaper than replacing the entire frame.
You’ll see a misted, cloudy, or milky appearance between the panes. This happens when moisture leaks into the sealed space due to a failed edge seal. A blown double glazing unit can no longer insulate properly, so replacing it restores both visibility and warmth.
Yes — and that’s one of the biggest advantages of double glazing glass replacement. If the frame is still in good shape, you can just replace the sealed unit. It’s a quick, affordable, and effective fix that restores insulation and clarity without the cost of new frames.
Definitely. Modern A-rated or low-E replacement glass units provide far better insulation, reduce heat loss, and can even help cut down your heating bills. If you’re already replacing a unit, upgrading to energy-efficient double glazing is a smart move that pays off in the long run.
Tip: Not sure what type of double glazing glass you need or need a custom size? Colourglass Glazing can supply and fit replacement double glazed units that match or upgrade your existing windows for better performance, comfort, and style.
Get Expert Help with Double Glazing Glass Replacement
Replacing double glazing glass can be a satisfying DIY project for smaller jobs, but when safety, precision, or upper-storey windows are involved, it’s always best to call in the professionals. At Colourglass Glazing, we specialise in double glazing glass replacement, misted window repairs, and full double glazed window upgrades across the Wirral and surrounding areas.
Our friendly, experienced team will inspect your windows, identify the issue, and provide a free, no-obligation quote. Whether it’s a single blown double glazing unit or an entire home that needs replacement glass windows, we’ll ensure your property stays energy-efficient, secure, and looking its best.
Ready to get started?
Contact Colourglass Glazing today for quick, reliable window glass replacement and double glazing repair services in your area. For more insights into professional glazing and bespoke glasswork, you can also explore Peter Lee Glass for inspiration and ideas.
