Insulate the top floor ceiling without a vapor barrier

Yes, I have also considered placing the vapor barrier from above.

Basically, the ceiling only consists of a kind of wooden paneling, into which one could glue the vapor barrier.

Here I only have concerns that I will not be able to seal the spots where cables come from below to above.

I am also worried about the wooden beams; wouldn't they then also absorb moisture from below.

Why isn't there simply insulation that is wrapped in vapor barrier foil or that has a foil glued on from below.

Yes, that's exactly how I actually imagined it, you would basically just have to make sure that the insulation is also vapor-permeable and can handle a little moisture. (Wood fiber insulation would actually be the right choice here, wouldn't it?!)

Here I only have concerns that I won't be able to seal the spots where cables go from below to above.

Not critical, since the attic provides enough air for drying. I just wouldn't do it completely without a vapor barrier.

I'm also worried about the wooden beams, wouldn't they also absorb moisture from below?

That's why "ideally from below". If you put one layer of insulation over the beams, the dew point should also be outside.

Why isn't there simply insulation wrapped in vapor barrier foil or that has foil glued on from below?

There used to be aluminum-coated mineral wool insulation mats. Maybe you can still get them. The problem was that they were often used the wrong way around and especially at the connection points there is naturally no continuous layer. That is of course better solved with a continuous foil. If you can still get those from a building materials dealer, that would be an option. But do not use two layers! If anything, the upper layer without coating.

Can what apokolok has presented really work? It would be completely new to me that there are constructions made without a vapor barrier, even if the ventilation is great.

The rules of technology assume that the attic space could potentially still be used as living space afterwards. You obviously have to approach that quite differently. But if it's only about insulating the ceiling and the attic space is completely unused and the roof is uninsulated and therefore very well ventilated, what is supposed to happen then? Moisture rises and is ventilated out. Even if it gets a bit more humid up there, there is nothing there that could be damaged. The insulation itself would be the only thing I can think of. But due to the ventilation, it is not at risk here either. You can also put a cool one in below as already suggested, but getting it truly airtight will not be easy. In that respect, I would skip it, put wool in, and that'll do.

We want to have the top floor ceiling insulated here or possibly do it ourselves.

And how would the professional have done it?

Next year or the year after, we will get blown-in insulation in the floor ceiling; if I insulate myself, it’s just a temporary solution or, if the self-insulation works, it will stay that way.

Huh? Is the same thing supposed to be done again?

We can’t be the only house that is finished but can’t be insulated without having to tear everything out.

As harsh as it sounds; but it would only be finished when it’s done properly right away.

So the company would also do it without a vapor barrier because there is no other option now.

The company also said that it would have to be done with diffusion-open insulation materials, you just have to make sure that if the roof is done, it remains a cold roof on the top so that the vapor can escape.

Of course, the problem is that moisture penetrates the insulation one way or another, whether diffusion-open or not, but this is exactly where the wood fiber insulation could help because it can absorb moisture to a large extent and also release it again later.

As I said, the roof only has tiles, no foil or anything else. So the vapor should be able to escape sooner or later without any problems.

What do you think about the wood fiber insulation and why shouldn’t it work like this, are there reasons for that?

The thing with if it had been done right from the start is harder said than done, when we bought the house it was already completely renovated except for the furniture, everything was finished, I don't think anyone would have torn everything out and redone it just for the foil.