ᐅ Insulation – Converting a Basement into Living Space

Hello everyone,

We are about to start renovating our purchased house from 1970.
Since we have quite a bit of space and could use the extra income, we are extending the existing one-room apartment on the ground floor by adding a basement room, so that we can rent it out as a 1.5-room apartment.

The additional basement room has a light well and is intended to become a bedroom later on.
Regarding ventilation, I plan not to install a door in the opening to prevent moisture buildup, and the window might be fitted with a trickle vent.

There is currently no insulation.

My questions are:
What is the best way to insulate against sound and cold?
What else should be considered for ventilation?
Are there any other important aspects I should keep in mind?

Unfortunately, the search function did not provide any concrete answers.

Thank you in advance.
Best regards,
Robin

Robin46 schrieb:

My questions are:
What is the best way to insulate against noise and cold?
What else should be considered regarding ventilation?
What other things should I pay attention to?

- Apply for a change of use permit with the building authority (building permit / planning permission).
- Consider whether such a hastily put-together apartment (without a door to the bedroom?!) is rentable at all (assuming the new space is even allowed to be used as living space).
- What kind of noise do you want to insulate against in the basement?

Robin46 schrieb:

The additional basement room has a light well and is intended to become a bedroom later.

A room with a light well is not considered a habitable room. What you do with your rooms is your responsibility. However, for rental purposes, this room would not count and would likely be seen only as a nice-to-have for the tenant. Charging rent per square meter for it is, as far as I know, not possible.

A basement room with a light well is not considered a habitable room in legal terms, as it lacks a second emergency exit—the first being the stairs leading up. But what if there is a fire? If a resident is harmed due to this (fire, gas, flooding), the prosecutor will definitely hold you accountable!

For each floor that contains a habitable room, a second emergency exit is mandatory, such as a window with minimum clear dimensions of 90 x 120 cm (35 x 47 inches) or 120 x 90 cm (47 x 35 inches), with a sill height of 90–110 cm (35–43 inches) (Brandenburg—your state or region may differ).

Additionally, in most states, a habitable room must have a window area of at least one-eighth of the floor area. Depending on the building classification, the minimum ceiling height per story may also be allowed to vary downward.

Which state or region are we talking about here?

No stairs are necessary to exit the apartment; there are two emergency escape routes, a large window, and a ground-level direct entrance to the house.
We are talking about Baden-Württemberg.
The floor-to-ceiling height is 2.45 meters (8 feet).
The light well is not the only window in this room; there is a large window at the front area.