Window Sealing Guide for Home Improvers

Why it’s important to insulate windows

Window sealing is a crucial part of window maintenance with several important purposes. Proper insulation ensures a tight seal between the window frame and the wall opening, which is important to prevent water from entering. Incoming water can cause extensive damage to window frames as well as the building, such as rot and mould, which can be expensive to repair and harmful to the indoor climate.

In addition, insulation plays an important role in the energy efficiency of your home. A tight seal helps keep heat inside in the winter and outside in the summer, which can lead to huge savings on your electricity bills. It also improves the overall comfort of your home by eliminating draughts and preventing noise from coming in.

Finally, properly maintained seals contribute to the aesthetics of the windows by providing a neat and finished look. This complements both the window framework and the overall appearance of the building. It is a good idea to regularly inspect and maintain the seals around the windows to protect your home and ensure a healthy and comfortable indoor environment.

When must window seals be replaced?

When you move into a new house or have had new windows installed, you can often assume that professional window sealing has been done as part of the installation process. This ensures that the windows are tightly sealed right from the start.

But sealing is not a one-time job. Elastic seals and compressed sealing tape last an average of five years, after which you should consider whether it’s time to replace them.

The seals wear down naturally over time and then start to crack or shrink. This means that they no longer protect as effectively against the elements. If this is the case in your house, make sure to replace the seals – even if it has been less than five years.

It is important to look out for signs that windows need new seals. If they look to be pulling away from the windows, if you see traces of moisture around the window frames, or hear more noise coming from outside, these may be signs that the seals are no longer providing the necessary protection.

In some cases, especially if the windows are very old and damaged, it may be more cost-effective to replace the entire window rather than just replacing the seals. If you would prefer not to do it yourself, you can hire a professional to replace and insulate your windows - that way you can be sure it is done correctly.

Interior and exterior window sealing

Understanding the difference between interior and exterior sealing is key to protecting your windows and doors from the weather. Internal seals ensure airtight insulation that helps keep heat inside and prevents condensation, which can lead to damage on the frames. Use a diffusion-proof seal on the inside to prevent moisture from entering from behind the frame.

Exterior seals, on the other hand, protect against rain and moisture from the outside. Therefore, you need to create a diffusion-proof seal on the outside that wicks any moisture behind the seal in order to prevent mould and rot. It is therefore important to fit both interior and exterior seals and perform the task correctly with the right material.

What type of seal should I use?

When choosing the right seal type for your windows, it is important to understand the differences and benefits of the different options. The most common seals types:

• Exterior sealant
• Sealing tape
• Caulk

Exterior sealant

Exterior sealant for windows and doors has long been a traditional method that is appreciated for its ability to match the aesthetic and functional integrity of older buildings. Specifically, lime mortar is known for its breathability and flexibility. So, when renovating or replacing seals in an old house, you should consider using exterior sealant.

Although home improvers can apply exterior sealant, it requires patience, proper preparation, and understanding of the material properties in order to achieve the best possible results.

Sealing tape

Sealing tape is a modern and simple solution for windows and doors used primarily for exterior sealing, since it is diffuse and keeps out rain. Although sealing tape is a simple solution, it is also a more expensive solution compared to other options.

Note that sealing tape, which is pre-compressed, has an adhesive side that must be applied to the window or door, not on the masonry. The tape is also able to expand, which means that it expands after a short time. Therefore, you should not pause once you have started the work.

Window caulk

Caulk, which can be based on various materials such as silicone, polyurethane or acrylic, offers great flexibility and is perfect for filling in crevices and joints where some elasticity is required. Caulk for elastic seals is especially useful around windows, doors, and other areas where movement or vibrations may occur. You can usually use a caulking gun to apply the product in the right places.

Which of the sealing options above you should choose depends on the specific needs of the project, including location, exposure to weather and water, and aesthetic considerations. By understanding the benefits of each type, you can make the best choice for your project.

You should also check with the window manufacturer what sealant they recommend you use for the window in their installation manual.

Don’t forget about insulation and backstops

Insulation and seal backstops are both important components in the sealing process that you should not neglect. Insulation plays an important role in maintaining the thermal integrity of the building by minimising heat loss and preventing condensation, which can otherwise lead to damage to adjoining and surrounding materials.

Backstops, often in the form of polyethylene foam, are used to create a uniform depth for the sealant and to ensure that the sealant does not stick to the surface. This allows for proper movement of the seal and extends its service life. This is especially important in elastic seals where the ability to absorb movements between building components is necessary.

Using insulation and seals backstops correctly not only improves the performance and longevity of the seal, but also contributes to a healthier indoor climate and lowers energy costs because windows and doors close tightly and are well insulated.

Window sealing: step by step

Do you need to seal windows but uncertain how to? Then follow our step-by-step guide describing the different steps in the process.

1. Remove old seals: Once you have found out which seals need to be replaced, remove the old seals. Use a joint scraper or knife to carefully remove the old seals. Be sure to remove all seals, backstops, and insulation. Be careful not to damage the glass or window frame! Exterior sealant can be easily removed with a hammer or chisel, and sealing tape and caulk can be removed with a standard hobby knife.

2. Clean the surfaces: Make sure the surfaces on which the new seals will be applied are clean, dry and free of dust and dirt. If necessary, use a vacuum cleaner to pick up loose material.

3. Insulate the cavity: The cavity can be insulated with glass wool, for example. Glass wool is available in strips of a suitable size for insulation. Make sure that the insulation is not excessively compacted, since air must be able to enter.

4. Install new backstops: Insert the round backstop, also known as a backer rod. Make sure you insert the right amount to give the seal the right shape. This is achieved when the backstop is correctly positioned. A rule of thumb is that the seal should be half as deep as the width of the hole. Once you have measured it, you can then calculate how deep the backstop must be inserted.

5. Prepare and apply the sealing products: No matter what type of sealing solution you choose (exterior sealant, sealing tape, or caulk), make sure you have all the necessary materials and tools ready so you can apply the seal to your windows or doors.

• Exterior sealant: If you use exterior sealant, you must first and foremost mix it into mortar. Follow the instructions on the packaging carefully to achieve the correct consistency. To apply the Exterior sealant, use a trowel to apply and shape the mortar between the window frame and the wall.
  
  
• Sealing tape: Measure and cut the tape to the desired length.
  Then remove the backing paper and apply the tape along the edge where the window meets the frame or wall. Press firmly for good adhesion.
  
  
• Caulk: Insert the caulk into a caulking gun and cut off the tip of the cartridge.
  When you are ready to apply the caulk, draw the caulking gun along the seal while evenly squeezing out the caulk. Make sure to fill the hole completely.

6. Smooth the seals: Use a putty knife/grout stick or your finger dipped in soapy water to smooth the seal for a neat and even result. Using smoothing liquid, which can be purchased in most hardware stores, allows you to fill more caulk afterwards. This will not be possible if you use soapy water, as new caulk will not adhere to the soap. 

7. Allow the seals to dry:  Follow the manufacturer’s instructions for drying time before painting or touching the seal.

8. Inspection: Inspect the seals for any holes or gaps and fix if necessary.

By following these steps, you can ensure proper and sustainable seals on your windows, contributing to a better indoor climate and greater energy efficiency in your home.