How do I check whether my windows are leaking?

One indicator of leaks can be that your heating is no longer working as well as it should. Timely sealing of windows and doors protects your living space from moisture and draughts and helps to keep heating costs low. There is a lot of talk about energy-saving glazing and highly insulated walls, but draughts from leaking windows also play a similar role.

Leaky windows are most frequently identified as the cause of excessive heating costs and the associated heat loss. But how do I find out whether my windows are still tight?

Please bear in mind that window seals are wearing parts. They are exposed to high thermal and mechanical loads on a daily basis over many years. They become tired over time.

When do I need to replace a window seal?

Depending on the wear and tear, the old sealing tape should be replaced after 15 years at the latest.

Replacing a defective seal not only helps you to significantly reduce energy costs, but also provides additional protection against noise, dirt and pollen.

Basically, you should first check your windows as follows:

  • Are the window seals present all the way around?
  • Are there any visible gaps or joints between the window frame and the seal?
  • Have the window seals become hard over the years?
  • Have the seals become severely deformed?
  • Are the window fittings still fully present and functional?
  • Is the window handle too easy to operate? (there should be some pressure)
  • Are the wall and window sill connections completely closed or sealed?

How can I find out if I have leaking windows and should seal them?

There are two practical tips for identifying leaky windows. How do I determine whether my windows are still tight?

  1. Burning flame: A leaky window can be seen by running the flame of a lighted lighter along the window sash and frame. If the flame moves unevenly, it can be assumed that air can penetrate from the outside and the window is not properly sealed. If this is the case, the windows are leaking and new window seals should be fitted.
  2. Paper test: Clamp a sheet of paper between the window and the frame. If the paper can be pulled out without resistance, the seal is inadequate.

A manual check for porous and hard spots can also be helpful.

At the same time, you can also check the connection joints between the wall and the window and the window sill. Here it is often sufficient to remove the old silicone and reseal.

Sealing windows - what can you do?

Here you will find step-by-step instructions for your leaking windows:

  1. Leaks in the window seal must first be located (see practical examples).
  2. The appropriate window seal must be determined. UPVC windows or wooden windows? We will be happy to help you choose the right seal. Simply send us a photo of the cross-section of your current seal. We will determine this for you and send you a free sample before you order so that we can find the right seal for you 100% of the time. Contact us here.
  3. You can install the window seal yourself.
  4. Maintain window fittings with silicone spray.
  5. If necessary, renew the wall and window sill connections on the inside with silicone. The silicone joints on the window sills are often affected here.
  6. If necessary, replace the window sealing tape on the outside or reseal the outside of the window with silicone.

Can I replace window seals myself?

Yes, you can replace window seals yourself. The old and porous seal should be completely removed. Then cut the new seal to size and fit it piece by piece. There are various options for fitting in the corners. You can find videos and instructions for self-installation here.

When replacing glass pane seals, professional advice should be sought, as removing the glass pane requires experience.

Should I replace my window seal if condensation forms?

There is no clear answer to this question. If your window seal is defective, cold air can enter the room through it and meet the warm air there. It is important to check the window seals regularly to prevent moisture damage and mold growth. In addition to a window or door seal that is no longer functional, condensation can also occur due to a leaking pane or a defective edge seal of the pane or a lack of sealing of the building structure.

Condensation on windows is caused by warm air coming into contact with cold surfaces. The warm room air settles on the coldest part of the window and water forms on the cool surface.

Which window seals are best suited for replacement?

Depending on the area of application, you can choose between different materials, which are responsible for the quality of the rubber seal. You can find a comparison here: Properties and materials.
An optimum sealing function also depends on the fit. Do you need a plastic window gasket or a wooden window gasket? We will be happy to help you choose the right seal: Contact. For the seal to be fully effective, it is important that the rubber is installed correctly in the window sash or frame. We will be happy to explain the installation process to you in detail. A good fit ensures effective sealing and therefore makes a significant contribution to the energy efficiency of the building.