Insulating the attic. Before or after the screed?

Hello everyone!

Would you insulate the attic BEFORE or AFTER the screed?

I am afraid that moisture will get into the insulation wool and will be difficult to get out again...

Of course, I will try to seal the vapor barrier as well (airtight) as possible. However, I can't promise it will be 100%... We are insulating the attic in addition to the last floor ceiling (this is done by the general contractor drywaller and thus (hopefully) professionally executed). However, the floor ceiling will only be insulated AFTER the screed.

How would you handle this?

I have time now to take care of the attic... The screed comes in 3 weeks...

In our case, the opening to the attic is sealed in front of the screed for exactly that reason

Place an electric dehumidifier in the attic, a device around ~200€ is sufficient, and run it as needed. That way you are on the safe side. Otherwise, you may have to ventilate constantly – if you even have the possibility there. Closing the opening also makes sense, of course, warm moist air rises and condenses in the roof.

You might put more effort into the vapor barrier than the main contractor. If possible, do the Blower Door Test before the interior cladding is installed.

Unfortunately, we don't have a way to ventilate up there.

But I plan to set up 2 dehumidifiers in the house anyway (rented).

But sealing the hatch would of course also be an option!

Only, ordinary tongue and groove boards are installed there. That must let quite a bit of moisture through, right?

Normally not, you still have the vapor barrier. Moisture comes through the tongue and groove boards if the vapor barrier underneath is not intact, which in this case would actually be good. But since you don't have a window, I would still place a small, inexpensive dehumidifier at the top and run it as needed.