When I invest house spirits on my buildings the construction time doesn't go down by the 1 hour as said by the text. The change is only somewhere around 30 minutes or so...

How do house spirits work?

Perhaps its scaled to be one hour during the effect of dark aura? But I think its a bug.

the 1 hour from 1 spirit goes down on the basic time of the time wats needed to build that building.

for example if its said that you hawe to build your factory for like 10 hours if you use the only 1 serf on the construction side he needs 10 hours to complete the building, you use the spirit and he needs 9 hours.

If you use 2 serfs then they need 5 hours to complete the building and 1 spirit then they need to build it 4:30 hours anymore because the spirit is taking only the hour from the basic time needed to build the building - the basic time is not changing even if you use 5 or 6 serfs

Thanks, mate.
It is easier to understand this thing now.