So-called drafts are promoted by leaks that occur exactly where different materials meet – for example at the window. Because wooden frames in particular work all year round (they expand when it’s warm and contract when it’s cold), there are small gaps between the seals and the natural building material. And it is precisely through these that the cold air can get unhindered from outside into the interior of the apartment, which in turn means that the radiators have to generate even more heat. This is not only noticeable in the energy costs, but also in the frame: the damp air makes it easy for mold. You can avoid both in good time if you seal your windows. You can find out what you need to consider here.

You can use a trick to find out whether a window is leaking: close all the doors and then light a candle (a lighter can also be used). Run these along the inside of the window frame. If this starts to flicker, you have discovered a leak. If you don’t feel comfortable with the fiery experiment, you can also use a sheet of paper: place it on a corner of the (open) frame and close the window again. If you can pull the blade out easily, you can assume that there is a leak. Especially if you retighten the screws with an appropriate tool and still get the same test result. Then it’s time to seal the windows.

There are now a variety of different materials that are suitable for window sealing. Self-adhesive sealing tapes made of foam, rubber seals, silicone or acrylic as well as window putty have proven particularly useful. But what are the differences between the various options and what are the advantages and disadvantages? An attempt at an explanation follows:

Sealing tapes made of rubber or foamThe self-adhesive tapes can be ordered in different colors and shapes (width and length are variable) and can also be cut to size afterwards, i.e. shortened. They are particularly suitable for window frames made of wood or metal to seal leaks. The advantage of sealing tape is clearly the low price, but rubber seals last significantly longer (up to eight years depending on the manufacturer) than foam seals, which only offer a short-lived problem solution of one to a maximum of two years. Installation is easy with both.

To find out how wide the seals need to be, you should measure the frames in advance. The best way to determine the gap size is to wrap ordinary play dough in cling film (you can also use felt or paper) and then place it between the frame and the sash – and briefly close the window. If you choose rubber sealing strips, you can choose between E-profiles for narrow joints and P-profiles for wide joints. Self-adhesive foam sealing tapes are also available in different sizes and colors (black and white).

Important: If your windows are made of plastic and already have prefabricated rubber seals, no more may be glued over them!

Silicone and acrylic Also with these two sealing options, the difference lies in the detail: While their consistencies are quite similar, window silicone or joint silicone has a rather shiny texture and acrylic sealant a more matte texture. The first material is water-repellent and elastic, while the second can easily be painted over – which is particularly important for wooden windows if they have to be repainted, for example. However, if you want to seal the windows in the bathroom, silicone is the better choice for the sanitary area – as it does not let water through, even in damp rooms.

Window puttyThe adhesive and sealant based on linseed oil was used decades ago – and is still suitable today for wooden windows that were sealed with the material. Because although window putty is waterproof and environmentally friendly, it doesn’t last very long. For this reason, leaks have to be repaired from time to time. To do this, the old putty only has to be heated, for example with a hair dryer, removed from the joints and refilled. The material is as elastic as play dough and can easily be molded into the desired shape. It then takes a few days to dry.

While sealing windows is certainly not rocket science, the following tips can help achieve a clean result:

Before you get to work, you should clean the window frames and the joints. Light dirt can be removed with water and detergent, for stubborn spots you can use alcohol, for example.

The old seals and adhesive residues must then be removed. A spatula can be very useful here to remove the residue. You can also oil any wooden fittings.

If you want to seal your windows with silicone, you can press some cling film or paper onto the material and wet it with soapy water. After that, close the wing to allow the silicone to dry.

Rubber seals are suitable for plastic windows: depending on the width of the gap, these should be between 1 and 3.5 millimeters thick. When attaching, it is important that the tapes are tight at the corners.

And one more tip at the end: Ideally, you not only seal your windows from the inside, but also from the outside – because there can also be weak points through which cold air can get inside the apartment. However, finding the leaks is a lot more difficult, so it’s best to focus on the obvious crevices.

This article contains so-called affiliate links. There is more information here.