Construction Experts Warn of Risk of Mold

Replacing Windows – and Doing It Properly

28. Jul 2016

Immobilienprüfung

  • Condensation can form on masonry
  • Overall energy concept required


In homes and apartments with older, poorly insulated windows, heating often goes “out the window” to a large extent. Fitting modern, energy-optimized windows often does result in lower heating costs. But if you don’t take care during the renovation, you may unexpectedly find yourself facing unpleasant mold growth in the residence, warn construction experts from DEKRA.

“The risk of mold formation when windows are replaced is related to better insulation values and the fact that modern windows are very tightly fitted,” explains Andreas Kraus, a construction and property expert at DEKRA. In the case of older, poorly insulated windows, condensation from the air in the room forms directly on the comparatively cold window pane.

“By contrast, modern windows are generally almost entirely draftproof and excellently insulated. This means that in older buildings with bricks that provide comparatively poor insulation. the new windows are then often warmer than the surrounding masonry. As a result, condensation no longer forms on the window pane, but rather in places that give off more heat due to construction- or material-related factors, such as in corners of the room, on window lintels and on the masonry of window reveals,” says Kraus. If moisture appears on a long-term basis, this can ultimately lead to mold growth with negative health effects and a bad overall living environment.

To solve this dilemma, the experts recommend seeking specialist support to coordinate the insulation values of the windows with the masonry. For those who wish to fit highly insulated windows for energy-saving reasons, there is generally no alternative to insulation of the external facade in the case of older buildings. If window replacement is planned in individual apartments and no complete external insulation is intended, this may be possible only in conjunction with well-planned and technically flawless installation of internal insulation. Accordingly, traveling window installation companies that advise private owners to replace windows without incorporating the measure in an overall energy renovation concept are to be viewed critically.

As a preventive measure to avoid mold formation in homes and apartments, it is recommended – including for modern, extremely thick windows – to keep the windows wide open for five to ten minutes for intensive ventilation several times a day.

Press contact:

Tilman Vögele-Ebering

Press officer Industrial

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