How to make an air conditioning window seal yourself

Creating a window seal for your portable air conditioning unit is surprisingly simple to do yourself. A well-fitted seal stops warm air from coming back inside, making your air conditioning unit more efficient and reducing energy costs. With some acrylic, you can quickly put together a solid seal that fits your window perfectly. Here's how to get started.

Before diving in, think about how you’d like to fix the window seal, as this depends on the type of window you have:

For outward-opening casement windows, glazing clips or velcro tape both work well.

For inward-opening windows, velcro tape is usually your best option. With this method, the acrylic sheet gets mounted to the inner frame.

Make sure your window can still open and close smoothly without the seal coming loose. This is particularly handy if you plan to remove and reinstall the seal regularly. Pro tip: adding a small handle will make it even easier to remove.

Good prep leads to a strong seal and prevents air leakage.

Take precise measurements of your window or frame before ordering your acrylic sheet. Record the width and height accurately. For example, standard tilt-and-turn windows might measure around 80 cm wide and 100 cm high. Are you planning to use glazing clips for installation? Add about 4 cm extra to ensure the sheet overlaps the frame adequately.

If your air conditioning unit has an extractor hose, you’ll also need to measure the required hole for the hose connection. Air conditioning hoses usually have a diameter of 12 to 16 cm. Unsure? It’s worth double-checking the size to get it just right. Add an extra 0.5 cm to the hose diameter for a better fit.

Once you have your measurements, you can easily have your acrylic sheet custom-cut to size with our sheet calculator. Input the exact dimensions - such as 80 x 100cm - and select the 4mm thickness option. With our precision cutting service, your sheet will arrive cut to the exact millimeter.

Want a pre-cut hole for your air conditioning hose included? Input the diameter of the hose during the order process (e.g., 16cm). If your window has an unusual shape, such as a rounded top, we’ve got that covered too; simply enter the specifics into our sheet calculator for a fully customised result.

Acrylic is the perfect material for this task - 30 times stronger than traditional glass, lightweight, and UV-resistant. This makes it particularly suitable for windows exposed to direct sunlight or outdoor conditions.

If you'd prefer to cut the hose opening yourself, you’ll need to do this carefully for a neat finish. Keep the protective film on the acrylic sheet during this step to prevent scratches.

Start by marking the opening with a pencil. To accommodate a hose, you’ll want to draw a circle, for instance, 16 cm in diameter. Use some painter’s tape to cover the outline. This keeps the markings visible while protecting the acrylic from damage during cutting.

Place the sheet on a stable, level workbench. Secure it using screw clamps, adding a soft material between the clamps and the sheet to prevent any marks or damage. Then, carefully cut out the circle with a circular saw or jigsaw fitted with a fine-tooth blade.

Take it slow and check your progress along the way to ensure an even cut. Once the hole is complete, smooth the edges with fine sandpaper for a safe, polished finish free of sharp edges.

Now that your acrylic sheet is all set, it’s time to install it. Begin by applying insulation tape along the edges of your window frame - this prevents air from escaping around the sides.

Next, depending on your chosen method of attachment:
Glazing clips: Secure the clips to your window frame and fit the acrylic sheet securely. Check that it stays in place without damaging the frame.
Velcro tape: Attach one side of the tape to the acrylic sheet and the other to the window frame. Make sure it’s properly aligned to create an airtight fit.

Press the seal firmly into place and double-check that all edges are tightly secured. If you notice any small air gaps, add more insulation tape to seal them up effectively.

Once the seal is installed, connect your air conditioning hose to the opening. Make sure it fits snugly in the hole to stop any air from escaping. Inspect the acrylic sheet’s fit around the frame to ensure there are no gaps.

Turn your air conditioning unit on and see how it performs with the new seal. If you sense warm air still getting in, it may be worth adding additional insulation tape. Proper installation ensures your room stays cool with minimal loss of chilled air.