How do you draught proof sash and casement windows?

Window Draught Proof

Creating a home that’s both comfortable and energy-efficient is a top priority for many homeowners. A significant factor that affects your indoor comfort is draughts sneaking through your windows. While sash and casement windows can add character to your home, they often let in unwanted cold air. An effective draught proof is crucial for maintaining a comfortable temperature, especially during colder months.

Identifying the Gaps

Before embarking on any draught proofing mission, locating the source of the draught is the first critical step. Run your hand slowly around the entire window frame and the moving parts of the sash. This low-tech method can be quite effective in identifying colder spots. Alternatively, a lit incense stick can be a valuable tool. If the smoke’s direction wavers while you run it around the edges of the window, you’ve spotted a draught.

Preparing for the Job: The Must-Have Materials

An efficient draught proof involves using the right materials and tools. Without these, you risk doing a shoddy job that doesn’t stand the test of time. Here’s a rundown of the essential items you’ll need:

  • Weatherstripping tape or V-strip
  • Silicone sealant
  • Door and window sealant
  • Caulking gun
  • Measuring tape
  • Utility knife
  • Cleaning supplies, including a good surface cleaner and cloth

Having all of these on hand before you begin can save you time and reduce the likelihood of unfinished work.

Draught Proofing Sash Windows

Step 1: Clean the Area

Begin by cleaning the entire window frame, focusing on the areas where the sash slides up and down. Dirt, dust, or older adhesive materials can interfere with new adhesives, making them less effective.

Step 2: Measure Twice, Cut Once

Once the area is clean, use a measuring tape to accurately measure the gaps around the window. This ensures that you cut your weatherstripping tape or V-strip to the exact length needed. It’s better to measure twice and cut once, as the saying goes.

Step 3: Application of Weatherstripping

Peel the backing off the weatherstripping and apply it to the frame where the sash comes in contact. Make sure the fit is snug by pressing down firmly. Double-check that the sash moves smoothly over the newly applied strip.

Step 4: Quality Control

After sealing the sash, it’s time to check your work. Close and lock the window, then use the incense or hand method again to check for draughts. If any gaps remain, reapply the weatherstripping where needed.

Draught Proofing Casement Windows

Step 1: Preparation and Cleaning

Like with sash windows, the first task is cleaning. Use a surface cleaner and cloth to thoroughly clean the areas where the window comes in contact with the frame.

Step 2: Seal with Silicone

Silicone sealant tends to be the preferred option for casement windows. With your caulking gun ready, apply a thin, even line of silicone around the edge of the frame where the window will meet when closed.

Step 3: The Finishing Touch

Use a specialised caulking tool or even a piece of cardboard to smooth out the freshly applied sealant. This not only makes the application look neater but also ensures that there are no gaps or bubbles.

Step 4: Dry and Test

Allow the sealant to fully dry based on the manufacturer’s guidance. Once it’s set, open and close the window a few times to confirm that it’s properly sealed and that the window functions correctly.

Annual Maintenance is Critical

Even the best draught proofing materials can degrade over time. It’s good practice to check the integrity of the weatherstripping and sealant at least annually. If you notice any issues, it’s best to replace the materials before the colder months set in.

Why Professional Help Matters

Though draught proofing might seem simple, complications can arise, particularly if your windows are old or have sustained damage. Professional expertise can be invaluable for addressing tricky situations and ensuring that the job is done efficiently. An expert’s involvement can not only make the process smoother but also offer longer-lasting results, potentially saving you both time and money in the long run.


Draught proofing sash and casement windows is a practical way to enhance your home’s comfort and energy efficiency. Although a seemingly straightforward task, it involves several steps, each critical to the overall success of the project. Remember, it’s often beneficial to consult with professionals for optimum results, especially if you encounter any challenges along the way. By taking the time to properly draught proof your windows, you’re investing in long-term comfort and cost savings.