Insulate attic / OSB boards

Hello dear house-building friends,

New build Kfw70 single-family house.

We are currently facing the decision whether to have our attic insulated immediately and whether to also have OSB boards installed at the same time. The carpentry company does not have a clear opinion on this.

I would like to hear a few advantages and disadvantages; at the moment I only see the financial aspect. Thus, both together would cost me about 2400 € net extra. My colleague said today that he wanted to save money on his new build but is now willing to spend it. He said he would have it done right away.

Sections attached.

Looking forward to your suggestions.

Disadvantage: costs money Advantage: then it is finished and done and you can properly use the attic right away.

We had it done at our current house and will have it done again at the new house immediately.

Yes, exactly, that's what I think too. Are there really no disadvantages except for the financial aspect?

Of course it exists, you then have additional storage space which you fill with unnecessary junk and eventually have to clean up.

But I would also let [it] be done right away.

Ok. Then maybe you can save some money if you only lay the OSB boards. The insulation doesn't seem to be absolutely necessary.

Thanks for the help!

But if you don't insulate at the top, you lose a lot of heat, don't you? Heat rises upwards, after all. Is your roof insulated all the way to the top?