ᐅ Door between basement and basement foyer (or basement lobby)

Hello!

We are building a single-family house with a basement. The basement will remain unheated, and the door between the anteroom and the basement should, according to the building specifications, comply with climate class 3.

Unlike the other doors in the house, this one is not included in the contract and must be installed as part of our own work. This is not a problem, but I still asked the general contractor for a price, and we were quoted a wooden door with the same beech wood finish as the rest for a hefty 1100 euros.

I declined this offer, as the price seemed quite high to me, and I don’t necessarily need the “perfect look” matching all other doors in the anteroom downstairs.

Now my questions:
Can I alternatively use an insulated steel door?
I was thinking of an “MZ-1 multipurpose door” by Hörmann, or something similar.
The thermal insulation value is given as K=1.7 W/m²K, but according to the description, it does not seem to meet climate class 3. Is this a problem?

Best regards,
Stefan