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Brian M. Jamerson
Brian M. Jamerson
Content Specialist

How to Install Replacement Double Glazed Units

Learn how to install replacement double glazed units with our step-by-step guide. Perfect for homeowners looking to improve energy efficiency and home comfort.
Replacement Double Glazed Units

Table of Contents

Maintaining your double glazed windows is essential for keeping your home energy-efficient and secure. Over time, these windows may not work as well because of normal wear and tear, such as fog forming between the panes, broken seals, or trouble opening and closing.

Installing replacement double glazed units can save you money on heating bills by preventing heat loss and keeping your home warmer during the winter months, as well as cooler during the summer. It contributes to a more sustainable lifestyle by improving your comfort and lowering your carbon footprint.

Plus, tackling this project yourself can be a rewarding experience for any homeowner or DIY enthusiast, offering a sense of accomplishment and potentially increasing the value of your property. Enhancing the performance and durability of your windows may be achieved by investing in top-notch double glazed units that have advanced features like low-emissivity coatings or argon gas filling.

Understanding Replacement Double Glazed Units

Understanding Replacement Double Glazed Units

Before jumping into the installation process, it’s essential to understand what double glazed windows are and how they work. There is a layer of air or gas, usually argon, between the two panes of glass in a double-glazed unit. This design significantly enhances insulation, reduces noise, and increases security compared to single-pane windows. The trapped air or gas acts as a barrier, minimizing heat transfer and keeping your home warmer in winter and cooler in summer.

Furthermore, the improved thermal efficiency of double glazed windows can lead to decreased energy expenses since a lower amount of energy is required to control the temperature of your home. The noise reduction benefits are particularly advantageous in urban areas or near busy roads, providing a quieter and more comfortable indoor environment.

Overall, double glazing not only improves the energy efficiency and comfort of your home but also contributes to a more sustainable living space by reducing your carbon footprint.

Signs You Need Replacement

Signs You Need Replacement

How do you know when it’s time to replace your double glazed units? Identifying the indicators at an early stage can save you from encountering more substantial issues in the future. Here are some common indicators that your windows might need replacing:

  • Condensation Between Panes: If you notice moisture trapped between the panes, it indicates a broken seal. It might encourage the growth of mold and lessen the insulating power of your glass.
  • Drafts or Cold Spots: Feeling drafts near the windows suggest that the insulation is compromised. Your heating and cooling systems will have to work harder to maintain a comfortable temperature in your house, which might increase your energy expenditures.
  • Visible Damage: If your windows have cracks or chips in the glass, they will look bad and not work right. Over time, these damages can worsen, leading to potential safety hazards and further reducing the efficiency of your double glazing.
  • Difficulty Opening or Closing: If you find it challenging to open or close your windows, it can be a sign of warped frames or faulty hardware. This may impact your home’s general security as well as the usefulness of your windows.

If you know these signs, you can change your double-glazed windows on time. It will make your house attractive, safe, and energy-efficient.

Preparing For Installation

Preparing for Installation

Before you start, make sure you have all the tools and ingredients you need for a smooth replacement:

  • Replacement double glazed units: Make sure they are the correct size and specification for your windows.
  • Measuring tape: Use this to get the correct measurements for the sizes of the new units you need.
  • Safety goggles and gloves: Protect your eyes and hands from getting hurt while the repair is being done.
  • Screwdriver: A versatile tool required to remove any screws holding the old units in place.
  • Utility knife: Ideal for cutting through caulk and other sealants.
  • Putty knife: Helpful for prying out old glazing and applying new putty.
  • Glazing tape or putty: It is necessary to secure the new glazing units.
  • Caulk and caulking gun: Use these to seal any gaps and ensure a watertight finish.

Taking the time to gather these materials beforehand will make the replacement process more efficient and safer.

Safety Precautions

  • If you want to stay safe around broken glass and sharp edges, put on safety glasses and gloves.
  • To avoid falling, make sure you have a safe, strong ladder with a solid base if you’re working on windows above ground level.
  • Make sure you work in a room with good airflow so you don’t take in caulk or putty fumes, which can be dangerous to your health if you do it for a long time.

Measuring for New Units

Accurate measures are needed for a job to go well. Commence by utilizing a dependable measuring tape to ascertain the precise dimensions of the height, breadth, and depth of the current window frame. Please take note of these measurements and double-check them to ensure precision.

It’s also a good idea to measure in multiple places to account for any irregularities or inconsistencies in the window frame. Record all your measurements clearly, and consider having a second person verify your results to avoid any potential errors that could affect the installation process.

Step-By-Step Installation Guide

Step-by-Step Installation Guide

Remove the Old Units:

  • Methodically remove any trim or molding surrounding the window with a putty knife. Be thorough and gentle to ensure you do not damage the wall or surrounding areas. If the trim is painted or caulked, you may need to score the edges with a utility knife to loosen it.
  • Unscrew the fasteners holding the window in place. Keep the screws in a safe place in case you need them later. It’s a good idea to label them or place them in a small container to avoid losing any.
  • Gently pry the old unit out of the frame with a pry bar or similar tool. Take extra care not to damage the window frame, surrounding walls, or any nearby fixtures like blinds or curtain rods. It may help to have a second person to assist in holding the window steady as you remove it, especially if the unit is large or heavy. Moreover, the utilization of gloves can effectively safeguard your hands against any injuries caused by sharp edges or shattered glass when engaging in this procedure.

Prepare the Frame:

  • Begin by cleaning the window frame thoroughly. Use a brush or a vacuum to remove all debris, dust, and any remnants of old caulk. This step is crucial as it ensures that the new installation can adhere adequately and look clean. Be meticulous, as leftover residue can affect the seal and overall finish.
  • Once the frame is spotless, carefully apply glazing tape or putty around the entire edge of the frame. This step plays a significant role in creating an effective seal for the new window unit, which is essential for preventing air and water leaks. Ensure the tape or putty is applied evenly and smoothly for the best results. If using putty, press it firmly into place and smooth it out to create an even surface that will help the window fit snugly.

Install the Replacement Double Glazed Units:

  • Carefully position the new double glazed unit into the frame, making sure it fits snugly. Take your time to avoid any damage to the glass or the frame.
  • Secure the unit with screws or brackets provided by the manufacturer, following their instructions closely. You may need to use a screwdriver or power drill for this, so make sure you have the right equipment on hand.
  • Verify that the device is horizontally level and correctly positioned by using a spirit level. Make any adjustments required to avoid gaps or misalignment, as these could lead to issues with insulation or window operation in the future.
  • Double-check that all edges are sealed correctly to prevent drafts and ensure maximum energy efficiency. Apply a bead of silicone glue around the unit’s sides and use a caulking tool or your finger to smooth it out.
  • After installation, clean the glass and frame to remove any fingerprints or smudges, and inspect your work to make sure there are no visible gaps or defects.

Seal and Finish:

  • Begin by applying a generous amount of high-quality caulk around the edges of the window. This step is crucial for sealing any gaps and preventing air leaks, which can improve energy efficiency and reduce utility bills.
  • Next, carefully replace the trim or molding around the window frame. Depending on the type of trim and window frame, make sure it’s lined up right and firmly in place using nails or screws.
  • After the trim is installed, use a damp cloth to wipe away any excess caulk for a clean and polished finish. It will guarantee that the caulk line has a polished, tidy appearance.
  • The last step is to let the caulk dry thoroughly before painting or sealing the trim. This drying period is essential to ensure the caulk sets appropriately and provides a durable seal. Drying times can be different for different types of caulk, so follow the directions on the package for the best results.

Tips For A Successful Installation

Tips for a Successful Installation

Check for Level:

  • Use a spirit level to ensure the window is installed straight. Over time, this will assist in preventing problems like inadequate sealing and water leaks. A level window also ensures that the sash operates smoothly and that the locks align correctly, which is crucial for security and functionality.

Avoid Over-Tightening:

  • Tighten screws just enough to hold the unit in place without warping the frame. Over-tightening can damage the window frame and reduce its effectiveness. It’s best to follow the manufacturer’s torque specifications to avoid compromising the window’s structure.

Use High-Quality Materials:

  • Invest in good-quality caulk and glazing tape to ensure longevity and durability. These materials will provide a better seal and withstand various weather conditions. Suitable materials may cost more at first to keep air and water out, but they will save you money and trouble in the long run.

Take Your Time:

  • As you rush, you might make a mistake. Take your time and make sure you do everything right, from measuring to closing the window. For the window to work well and last a long time, it must be installed correctly. Double-check all measurements and alignment before finalizing the installation to ensure a perfect fit. Remember, a well-installed window will contribute significantly to your home’s energy efficiency and comfort.


Regular maintenance and timely replacement double glazed units are crucial for the longevity and efficiency of your windows. By following this guide, you can tackle the installation yourself, saving money and ensuring a professional finish. If you found this post helpful, share it with fellow homeowners and DIY enthusiasts who might benefit from these tips. Happy installing!

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