ᐅ Retrofitting a Central Ventilation System for the Attic

Good morning,

we are planning a KFW-55 house with a central ventilation system. The attic will initially be unfinished but is intended to be converted into living space later on.
Is this straightforward to implement? What should be considered? Does each room require its own supply and exhaust duct, and should the exact number of rooms already be determined? Is this even feasible, or would it be better to plan a decentralized solution in the attic, for example, using Velux roof windows?

Just plan it with your designer from the start and have the pipes installed during the rough-in phase.

A tip: if you plan to tackle this soon, have the attic conversion done right away. It involves a lot of mess and effort, and afterward, you really won’t feel like doing it.

I can confirm that. I've wanted to address it for years, but nothing has happened in the last five years, and yes, there is also the issue with the pipes. Everything needs to be installed beforehand; afterwards, it either isn't possible anymore or only with special solutions. Alternatively, there are decentralized systems or no ventilation system at all, relying on manual ventilation through windows.

At the moment, it is unfortunately not financially feasible, but we definitely don’t want to limit ourselves for the future. What exactly needs to be installed overhead? Is one pipe for supply air and one for exhaust air enough, or does each room require its own?

It depends on how the rest of the system is designed. The system would also need to have enough capacity to supply an entire additional floor later on.

In this case, it might actually be more cost-effective and simpler to relocate the entire system to the attic (the system and pipes need to be insulated as long as the space is not finished).