Ventilation system with heat recovery, installation location temperature

Is it true that a controlled residential ventilation system is not allowed to be installed in an uninsulated attic?

If you build an insulated enclosure and insulate the pipes, then yes... otherwise, it will rain from the valves...

As already mentioned, a temperature of 12° must be maintained year-round at the installation site of our Pluggit system.

The ventilation installer had to confirm this in the commissioning protocol (in our case my brother-in-law, since it was own work).

When I open the roof hatch, the temperature in the attic rises and the temperature of the air being blown out rises to 20/21 degrees. When the hatch is closed and the attic is only 15 degrees, the blown-out temperature is 16 degrees.

Interesting, I would not have expected that. Do you have a leak in the "blow-out" duct in the attic? I can't make sense of that right now without further knowledge of your system.

Hello, in the attic where the system is located, there is also a supply air and exhaust air vent. The exhaust air that is sucked in from the attic is naturally colder than from the other rooms in the house. If I now leave the attic hatch open, the temperature in the attic will rise and warmer air will be sucked out! That is why I am considering enlarging the radiator in the attic to increase the efficiency of the system?

That's why I'm considering enlarging the radiator in the attic to increase the system's efficiency?

Now I understand which temperatures you mean. No, that does not increase efficiency. The degree of heat recovery is always less than 1. For every additional kW that you put into the attic with the heater, you only get part of it back. The other part is lost.

I believe that remains the case even when looking at the entire system (i.e., the balance over the entire controlled residential ventilation, not just the attic), but I'm currently too lazy to calculate it or come up with the necessary assumptions :P.

The exhaust air from the attic is only a (small) part of the total exhaust air.