Revisions log for Answer #1058
This is the answer to the question How to install extra ventilation in an old building with new windows?
Revision 1
If you have to get KfW funding as a separate measure to replace the window, the U-value of the wall should not be lower than the window. This needs to be checked, otherwise there really is a risk of condensation and mold on particularly cold areas of the unmaintained exterior wall. Your energy consultant should know this, especially if he is applying for and supervising KfW measures as a qualified expert.
When replacing windows the ventilation concept according to DIN 1946-6 must also be developed. The required air exchange rate can be achieved, for example, by decentralized ventilation. If necessary, so-called window rebate ventilators installed in the window frame are sufficient. This must be verified by calculation.
You need an energy consultant to work out a concept for the renovation of the building as a whole. All measures must be coordinated with each other and with transitions.