Insulate cold roof with clamp felt, price

but do you have to spend a few thousand euros so that paint residues don’t freeze?

I agree with you. I would probably build an insulated chest for the few things that should not get too cold rather than insulating the entire storage room. Most of the space up there is enclosed space that just sits idly and basically only exists because one wants standing height in the attic.

Well, actually I tend to trust a professional there.

I am astonished. Your construction must have gone extraordinarily well for you to still think that way

The whole thing is nonsense for two reasons:

1) The attic is so cold because you withhold your living room heat from it through the insulated top floor ceiling; it won’t suddenly warm up on its own just because you throw in a few more square meters of insulation wool. Frost protection: none. Only heat protection improves.

2) You want to wrap your attic all around in foil. Of course that is possible, but it carries risks as soon as it gets damp up there somehow. Normally the water would dry out because the roof space is well ventilated. That possibility disappears when you wrap the roof.
Apparently your "professional" also sees that moisture could get there, otherwise he could dispense with the (additional) vapor barrier and leave the insulation open.

As for the price, it also depends on what you get for it.
In the simplest form, he would screw a batten across behind the knee wall so the insulation doesn’t fall down, stick the vapor barrier visibly onto the rough sawn boards, and simply pull it over the knee wall and rafters in the walkable area. Then screw a simple layer of drywall directly on top, done. And I am just reading that the price is without puttying.

For this scope of service (which would be sufficient for an attic), I would find the asking price a bit steep. Two men should be finished after 2 days at the latest. (32 hours at €55 gross = €1760 + material = ~€3500)

However, if he crawls behind the knee wall, mounts OSB all around on the floor there as a connection option, primes nicely, then fiddles the vapor barrier around the knee wall, sticks nail sealing tape to the rafters, adds battens to straighten the structure, slams 2 layers of drywall on it and roughly putstys everything once including corner protection strips and so on, that would, of course, look completely different.

Your sweetheart in summary:

You want to spend money so your leftover paint can be nice and warm. The "professional" is offering you basically an overpriced solution for that (why, for example, even bother with the drywall cladding? You didn’t even lay down the rough sawn boards), which does not solve your problem and, on top of that, significantly increases the risk of structural damage. He winks at you confi­dently and certifies you had a good idea – completely without ulterior motives.

I stick to it: If you want to spend money on something unreasonable anyway, make sure it’s fun for you

Hello Karsten, my opinion is also rather negative towards the project. Two reasons for this:

1) Despite the patio door and vapor barrier downwards, moisture will slowly migrate in. Even just with every opening of the door.

2) Regarding your whole philosophy, the project is like the proverbial hunting sparrows with cannons.

If you need more constant (or at least warmer in winter) conditions for certain things, 11ant's very good idea is a much more sensible solution. Place a freezer chest with an intact seal, which you don’t operate. Inside it is cooler in summer, warmer in winter, all good. Or are we talking about storage goods in the range of several cubic meters?

Hmm, one has to think about that again before it becomes an order. Give us a break now.... I'll get back to you. K.

The project has been buried by my wife and me today. She is now blowing the money in the garden. She can easily manage that. Karsten

Can I join in here? The topic is already settled.

In our case, the roof and ceiling cavity are insulated, the quality of the vapor barrier between the upper floor and the roof is moderate – it was an issue during the BDT and was certainly not perfectly repaired.

The controlled residential ventilation is located in the roof. Our planner thought it was a good idea, and apparently it is not entirely uncommon. However, in hindsight, I would have done it differently.

How can I detect damage and how can it be avoided? Are there limit values for humidity or similar that I should monitor?

I could easily ventilate the attic via the controlled residential ventilation, but the controlled residential ventilation has moisture recovery. Is that sensible?