ᐅ Central ventilation system — is it advisable to install it in the basement as well?

Sorry, but in my opinion, that is not correct. Do you have any evidence for this? What exactly is supposed to happen?

An unheated basement room is not cold (it does not drop below 16°C (61°F) in the coldest winter), nor does the mechanical ventilation system bring in moist air—especially not when it is exhausting. The temperature due to the mechanical ventilation will not change significantly either.

I don’t see a problem here; quite the opposite.

LuckyDuke schrieb:
He also mentioned that in an unheated room, moisture could form due to the supply of warm air. This point actually seems logical to me, as moisture from the warm supply air condenses on the cold surfaces.

We currently have the exact opposite effect in our (rented) house.

The house (built in 2009) has underfloor heating/gas, an unheated basement that is not thermally separated and has no separating door, and a mechanical ventilation system with exhaust in the basement. When the mechanical ventilation is off for several days, humidity rises in the basement. We once turned off the mechanical ventilation during a vacation. After 14 days, the whole house smelled musty/damp starting from the basement. Two days after turning the mechanical ventilation back on, everything was fine again.

We only heated the hallway in the basement. Mechanical ventilation with heat recovery was installed only in the utility room. In hindsight, it would have been better to have mechanical ventilation in the other rooms as well (supply air in the hobby room, exhaust air in basement areas 1 and 2).

Bookstar schrieb:
Do you have any evidence for that?

Should I now give you the ISBN of my physics textbook?

Example:

Air at 21°C (70°F) with a relative humidity of 50% contains about 9g of water per cubic meter and has a dew point just above 10°C (50°F).
This means that as soon as this air cools below 10°C (50°F), water will condense out until the dew point is reached again. This usually does not happen indoors because all surfaces are warmer than 10°C (50°F).

An unheated basement is standardized to have an air temperature of 10°C (50°F) (especially if it is thermally separated from the living space above by insulation). If the 21°C (70°F) warm indoor air from above cools down to 10°C (50°F), the relative humidity rises to 97.5% and the dew point drops to just above 9°C (48°F). In a basement at 10°C (50°F), there are almost always surfaces colder than this 9°C (48°F) level, and those surfaces will then become damp.

Fuchur schrieb:
Basement unheated, not thermally separated, and no separating door

In this case, the basement is not really "unheated."
Of course, this can be solved that way, but I think most people do not want their expensive heated indoor air to simply be lost through the basement. Once the basement is thermally separated and a door prevents uncontrolled mixing with the living space air, the example given for @Bookstar applies.

I did not build the house

Yes, thanks for the example, but I already knew that myself. In fact, this no longer applies to any new build and is therefore purely theoretical.

As you can see here, in practice it is much better to connect all rooms. And if it costs 3 euros per year, I would consider the reduced risk of mold worth it!

Your initial post is incorrect and unfortunately does not help the original poster.