Retrofitting the roof with better insulation from the inside

Hello everyone,

we are owners of a maisonette apartment (2nd + 3rd floor) in a 6-family house, built in 1993. Unfortunately, it is clearly noticeable that the more roof surface the rooms have, the warmer they are in summer and the colder in winter. The roof surfaces are lined with tongue-and-groove wooden panels. You can even feel quite a draft when you place your hand on the gap between the panels and the wall. Especially when we remove the recessed lights from the ceiling, the draft is very noticeable.
Attached is a picture I took through the opening of the recessed lights: You can see the rafters (estimated 10-15 cm deep) and between them many narrow polystyrene boards (5 cm wide, 5 cm less deep than the rafters).

Now I have 2 questions:
1. Is this normal for a house built in 1993 or can this be considered a construction defect? I would have expected something different from this construction year, but I am not an expert.
2. How can I most pragmatically improve the insulation from the rooms? The sloping roof affects both our 2nd and 3rd floors. Unfortunately, we do not have an attic, which, as often depicted on the internet, consists of only one room.

Thank you very much for your support!!
Regards
Mischa

Hello Mischa,

to effectively improve the thermal insulation and get rid of the drafts, I would do the following:

- Remove the interior cladding of the sloping roof
- Remove the Styrofoam from the spaces between the rafters
- Insert mineral wool
- Install a vapor barrier and seal it airtight

For improving the summer heat protection, an external renovation with the installation of, for example, wood fiber insulation on the rafters would be more suitable, but of course the effort is much greater.

Personally, I do not consider the insulation to be a defect. But in renovations, I have not seen something like this so far, only in a similar form.

You can then attach a substructure to the vapor barrier and install the new cladding, e.g., drywall panels.

Regards Daniel

Hello Mischa,

to effectively improve thermal insulation and get rid of drafts, I would do the following:

- Remove the interior cladding of the sloping roof
- Remove the Styrofoam from between the rafters
- Insert mineral wool
- Install a vapor barrier and seal it airtight

For improving summer heat protection, a renovation from the outside with the installation of, e.g., wood fiber insulation on the rafters would be better suited, but the effort would of course be much greater.

Personally, I do not consider the insulation to be a defect. But in renovations, I have not seen anything like this so far, only in a similar form.

You can then attach a substructure to the vapor barrier and install the new cladding, e.g., plasterboard.

Regards Daniel

The only problem is that you are not allowed to do any of these things without the approval of the homeowners' association. In addition, each of the 6 parties would have to pay for the unnecessary renovation through the provisions. A condominium remains a condominium. Everything beyond the wallpaper of your apartment is (I believe) subject to approval, but you know that as owners.