Replace plastic windows - what should you pay attention to


The window replacement is often advisable for energetic reasons, sometimes a better noise protection is required than is available. What to think about when replacing windows, read in this post.

Lifetime of windows

Plastic windows usually reach the end of their life after 20 to 40 years. At this time, many windows have to be replaced just for technical reasons.

However, high-quality windows, which do not yet have functional defects, can generally remain in the building as long as there are no other reasons against it. That can be different reasons.

Heat protection as a reason for exchange

Above all, windows that were installed before 1995 usually have catastrophic U-values. Compared to modern energy-saving windows, these windows lose an enormous amount of heat.

Replacing the windows often pays off very quickly through significant savings in heating costs. How long this amortization period is depends on several factors:

  • the size of the total glazed area
  • the difference in U-values ​​between old and new windows
  • the type and efficiency of heating but also
  • from the price of new windows and
  • possible subsidies and tax deductions

Influence of heating

The efficiency of heating is a frequently underestimated criterion. When switching to a more effective heating (gas fired condensing boilers have an efficiency of more than 100 percent) usually results in a completely different amortization situation.

The price of the heating material also plays a role in the amortization period. Thus, the savings in the very low-cost biomass heating, such as woodchip heaters, significantly lower than oil or gas as a heating medium.

Optimum amortization period

The potential savings after a heating optimization should be such that the windows have paid for themselves after ten years, if possible. As the life of plastic windows can sometimes be as little as 20 years, you should never have payback periods that exceed this period. Then a window exchange is not really worthwhile.

Tips & Tricks

Never rely blindly on the results of a "savings calculator" on the Internet. These computers are usually provided by a window manufacturer, who of course wants to sell his products. Often the values ​​for old windows are set too high, or the savings are exaggerated generously. It is better to rely on the calculation by an energy consultant who also uses the actual power values ​​of your heating system.


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