Experience ventilation roller shutter box: Aereco Zuroh 100

You, if the ventilation has a non-bypass capable heat recovery. Then it nicely warms the left air from outside again. What is desired in winter and saves heating energy is really annoying in summer. Maybe there is a button or error for that after all?

But the mentioned variant doesn't have any heat recovery at all?!

You, if the ventilation has a heat recovery that is not bypass-capable. Then it nicely reheats the left air from outside. What is desired in winter and saves heating energy is really annoying in summer.
Maybe there is a button or an error for that?

That is just a defined slit in the roller shutter box, nothing more. No heat recovery. If I look at the picture, the box measures 20-25 cm with a rotary knob for manual ON/OFF, otherwise "automatic". That’s it.

: So now 17-degree cold air should flow in when you set it to ON.

Yes, that's true, a box with a slot and then also a button to close it tightly. I ventilate for hours at 18 degrees and the temperature stays at 25 degrees. The cheapest of the cheap was installed there by the property developer. You are always wiser afterward. But I have since researched and found new cover plates for the inside with a button for retrofitting the Zuroh 100 to Zuroh 110. Let's see if it gets better. Thanks for the answers.

Addendum to the 2nd sentence shall read WITHOUT button

And again. That has nothing to do with it. Thermal insulation and shading are the "magic words". Describe the object. Wall structure? Apartment completely on the south side? Attic?