I have been installing HVAC in my 60 years old building.
When I made the contract I asked for metal ducts assuming they are durable in the long term. Now I looked in the attic and only a small part is metallic and the rest is flexible aluminum.
I am am thinking he has done so assuming being a woman I won't go look?
My attic is pretty tight and I guess it is much harder to work with metal there.
Should I object?

I have been installing HVAC in my 60 years old building.
when i made the contract i asked for metal ducts assuming they are durable in the long term. now i looked in the attic and only a small part is metalic and the rest is flexible aluminum.
I am am thinking he has done so assuming being a woman i won't go look?
my attic is pretty tight and i guess it is much harder to work with metal there.
should i object?

Aluminum is metal but my main concern is you did not mention weather the aluminum is insulated? All metal duct in the attic must be insulated or you will pay the piper when you get your utility bill. Another fact is in a attic or crawl space it is usually code to run insulated flex duct properly supported or ridged metal duct that is also insulated. Properly insulated metal duct jobs will cost at least 2 to 3 times as much as a insulated flex duct job. Did you get a building or HVAC permit? The plan review that goes along with the permit would have saved you big bucks if all of this stuff he has done is going to cause a problem.

Good luck.