April 26, 2026, 4:32 am | Read time: 3 minutes
When temperatures rise, a frequently overlooked part of the house comes into focus: the windows. Especially after the cold months, weaknesses become apparent here that not only affect living comfort but can also waste energy. Those who act now and maintain their windows can avoid major damage–and save real money.
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Why a Spring Check is Sensible
Leaky windows lead to significant energy losses during the heating season, and moisture can also penetrate. Therefore, homeowners are advised to use the warmer season to maintain and carefully care for their windows. Checking the seals is particularly important.
According to the Association of Private Builders (VPB), these can be kept supple with petroleum jelly, for example. Proper application is important: The seals should first be cleaned of dust and dirt. Then, the petroleum jelly is thinly applied with a soft cloth or finger and lightly spread. Wiping off is usually not necessary–it forms a protective film. However, excess material can be removed to prevent stickiness.
If you don’t have petroleum jelly on hand, you shouldn’t use other skin creams or lip balms as alternatives. They often contain water, fragrances, or other additives that can attack the material or do not provide lasting protection.
If the seals are greased once a year, they remain flexible and fulfill their function longer. Petroleum jelly is a simple home solution. However, special care products from specialist retailers, such as silicone-based greases, which are tailored to the materials of modern seals and last longer, are even better suited.
Regularly Maintain Window Hardware
Not only the seals need attention, but the window mechanics should also be checked regularly. “It is also advisable to maintain the window mechanics once a year,” says Andreas Garscha from the VPB. Since hardware is heavily used by frequent opening and closing, maintenance is essential. “Lubricating the window hardware with acid- and resin-free oil contributes to durability,” says Garscha.
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Check Wooden Frames After Winter
Windows with wooden frames should be inspected particularly carefully after the cold season. Damage from weather influences is not uncommon. If the paint is already peeling, the surface should first be lightly sanded and then repainted.
If the frames are rotten, cracked, or otherwise damaged, a complete replacement may be necessary according to consumer centers. This is especially relevant because the frame makes up to 30 percent of the total window area and thus has a significant impact on insulation performance.
Seals Can Be Tested with a Simple Trick
Whether windows still seal properly can be checked with simple means. You can already determine with your hand whether a draft is noticeable when the window is closed. A candle flame also provides clues: If it flickers near the window, this indicates leaks.
According to the VPB, smaller problems can often be remedied with foam or insulation strips. However, caution is advised: Too strong a seal can impair air exchange and, in the worst case, promote mold. Experts can better assess the situation. If seals need to be replaced, consumer centers recommend models made of rubber-like material instead of simple foam strips.
With material from dpa