Don't forget the chimney!

One important building element is often overlooked during renovations: the chimney. This is according to the Association of Private Building Owners (VPB). When an old heating system is replaced with a modern system based on low-temperature or condensing technology, the chimney system must be adapted to the new technology.

In many cases, chimney renovation also necessitates modifying the chimney to a suitable diameter, as modern heating systems require significantly smaller flue diameters. In other words, old chimneys are oversized for modern heating systems. If the chimney is not adapted to the latest technological standards or replaced, this can lead to consequential damage: Because modern boilers utilize combustion heat much more efficiently, the combustion gases enter the chimney at a considerably lower temperature, thus reducing the buoyancy of the exhaust gas produced during combustion. This, in turn, can cause the exhaust gas to cool down so much within the chimney flue that it condenses on the walls and dampens the chimney from the inside.

Soot buildup in the chimney

The exhaust gases also contain a high proportion of water vapor and sulfur compounds. These sometimes corrosive substances also condense on the inside of the chimney. Over time, they penetrate the masonry, leaving behind yellow-brown stains and a foul odor. This penetration of the chimney's outer walls by water, tar, and acids is known as creosote buildup.

Modern chimneys must therefore be not only fire-resistant and structurally sound, but also resistant to acids and moisture. Acid-resistant liners made of stainless steel, ceramic, or plastic, which are inserted into existing chimney flues and simultaneously reduce the cross-section, offer a solution to soot buildup.

Since there are different construction methods for chimneys, you should definitely consult the responsible chimney sweep before any renovation work; he will also inspect and approve the chimney.

Sources: dejur.org, juris.bundesgerichtshof.de, verbraucherschutz.tv, mietrecht-reform.de, n-tv.de, de.reuters.com, news.immowelt.de, anwalt24.de, augsburger-allgemeine.de, spiegel.de, sueddeutsche.de