Air conditioning is not necessary as far as I know as castles are cool by themselves thanks to thick walls (moats) etc.
I have yet to see the first fully heated castle, that would really be bad for the enviroment.
Originally Posted by Lalla Meriem
They do not use private jets. They travel commercial flights.
Pictures of Fischbach and Chateau de Berg always show windows open (I doubt these historic properties have air conditioning anyway) so they don't use excessive air.
Luxembourg is European and it's typical that everyone recycles even McDonald's sorts rubbish for recycling. They even reuse and share their clothing.
Guillaume is very concerned with the environment. He gave an interview a few years back where he stated that his future wife would need to be concerned with the environment (and no I didn't save the article so no link).
The family owns large tracts of forest which are preserved. I think it's safe to assume they care for the environment.