ᐅ Insulating a Concrete Ceiling on the Upper Floor / What to Consider?

Hello everyone,

The shell of the house is finished – the windows are still missing but have a delivery time.
In the meantime, I would like to insulate the upper floor ceiling (concrete) and cover it with OSB boards.

Facts:
- 2-story building
- Upper floor ceiling made of concrete – 20 cm (8 inches) thick
- According to the energy saving regulations certificate for KFW 55, the ceiling must be insulated with 18 cm (7 inches) of polystyrene
- The attic will not be used as living space, only for storage
- The purlins rest directly on the concrete ceiling
- The roof will not be insulated, so the floor will be insulated instead.

Questions:

1) What preparatory work do I need to do on the concrete before starting? Deep cleaning? Any ideas?
2) Do I also need to install a vapor barrier foil on the ceiling of the upper floor?
3) I plan to install the XPS panels in two layers of 9 cm (4 inches) each, staggered to ensure closed joints.
4) Then the OSB boards on top (thickness – no idea – any recommendations?)
5) Should I run the necessary electrical cables into the attic first (for lighting, power, and possibly an access point)?
6) Which boards would you recommend? Has anyone had experience with these?
7) Are there any special considerations I might not have thought of yet?

Looking forward to your opinions/ideas/tips and tricks.

Piotr

And one more thing: What exactly are these polystyrene boards? Are there any cheaper alternatives? What is the difference between EPS and XPS?

If I were you, I would insulate the roof...
You can’t create more storage space than that!

And the work involved is (almost) the same, I would say...
It may cost a bit more, but that’s nothing compared to the amount of storage space gained.

I wouldn’t put the panels in the roof. If there’s a fire, you won’t need the fire department.
Suggestion:
Apply 8cm (3 inches) of stone wool insulation on the concrete ceiling, then install the OSB panels. Additionally, include insulation between the joists.

For this purpose, there is a product from the company Bauder called PIR DHW or similar, which is an insulation material with an OSB board already attached.

Golfi90 schrieb:

If I were you, I would insulate the roof...
You can’t create more storage space that way!

But you can also store things in the attic if the roof isn’t insulated. We’ve been doing that for years and are happy with it.

K1300S schrieb:

You can still store things in the attic if the roof is not insulated. We've been doing that for years and are happy with it.

Not if it is a KFW55 house.
This is required by the energy saving regulations.