TGA planner/heating system, affordable construction planning preferred for single-family house

... only, there are also white sheep...

Certainly, < 5%, you really have to be lucky. Furthermore, the white fur is hardly visible in the fog.
If there is even a controlled residential ventilation with/without heat recovery, it becomes really critical!
Most HLB fail here due to formal or systematic errors. And the component geometry or properties have not even been checked yet!

Regards.