Wall box for extractor hood

Basically, it is the case that a fan becomes a) louder and b) the performance decreases with increasing back pressure. The smaller the cross-section, the longer the pipe, and the more bends there are, the higher the back pressure. General statements are difficult to make. Generally, DN150 is recommended today. My personal experience is: do not do without separate fresh air supply. Always tilting the window is annoying! With a chimney, you probably need the window contact without separate fresh air supply.