Renew roof insulation from 1986?

Hello,

I recently bought a terraced end house built in 1986 and am planning the upcoming renovation work. Now I am wondering whether I have to renew the roof insulation for better heat and cold protection. Because now would be a good time, as we are not yet living in the house.

It is a pitched roof that spans over 2 floors (of 3). The attic is finished as a room and there are radiators and two roof windows (Braas) on each side. Ceilings and walls are clad with wooden slats; on the 2nd floor the walls and ceilings are clad with gypsum boards.

The following is stated in the building description: "Rigips on counter battens, 10cm mineral wool, intermediate joists, air space – concrete roof tile." A vapor barrier/foil can be seen.

In some places in the attic, the wooden beams have bowed forward slightly and can no longer be pushed back by hand; also, some of the wood cladding is missing in places, leaving the insulation exposed. I have read that until the 90s carcinogenic mineral wool was installed. Unfortunately, I do not know which type is in my house. For this reason, should the insulation already be replaced?

According to the previous owner, there is only a draft in the master bedroom 2nd floor from the wall inspection flap. Otherwise, there is nothing unusual in winter or summer.

What do you say – replace or leave it?

You are in any case obligated to insulate the roof in accordance with the Energieeinsparverordnung; 10 cm doesn't really sound like that.

Hmm, where can I check if I have to do that. Do I have a significant heat and thermal protection because of the new insulation (Zwischensparren / Untersparren)? I have not opened the roof yet and can provide few details at the moment, but what is used for insulation today (good price/performance ratio)? If I should insulate, I would like to use plasterboard instead of wooden slats in the attic.

Well, that depends on various conditions; an expert is most likely to provide information on that. But even if there is no obligation, I would assist in view of our upcoming summers. It should be around 30 cm. Mineral wool or blowing in, there are different options.

I recommend either doubling the beams or additionally installing insulation under the rafters. For that, I would use rock wool at maximum thickness. I wouldn’t start with less than 20cm (total). More is often better. Additional mass, meaning heat protection, you get through OSB3 panels as a vapor barrier. These must be glued meticulously and sealed to the wall. Then preferably gypsum board on top. If you don’t do this now, you will be really upset. At the latest next summer! 10cm is practically nothing. And in terms of price, you can manage well with that. Without knowing current material prices, I would estimate around €2000 and 1 week of work. By the way, a job that can also be done by a layperson.

Isn't 30 cm a bit exaggerated? You lose a lot of living space because of that. 24 cm are often seen even in new buildings, so why at least 30 cm in an old building?