Our AC was blowing into an entire half of the house that is closed off and unused.

Hi all, I’ve been living in a 3 bedroom 2 bathroom house for 1.5 years now. This house was originally a 6 bedroom 4 bathroom house that the realty group who acquired it 4 years ago literally sliced in half and never finished constructing. No one lives in that half of the house and there are no doors into it. My curiosity finally got the best of me and I climbed through the unlocked window (which I presume is what the builders were using to get in and out of it since there are literally no doors) and what awaited me were 3 entire bedrooms, 2 bathrooms with showers, and the AC from our part of the house blowing into it. It was ice cold in there. The entire time, my roommates and I have been living here with our AC cooling down 3 bedrooms worth of square footage when absolutely nobody lives in there. I decided to shut every vent while I was in there so that it hopefully doesn’t waste even more cold air, but my roommates and I are very frustrated about my finding. Our electric bill is EXPENSIVE in the summer. It was $500 this month alone because of how hot our area is. I have to imagine that a decent amount of that electricity was the AC unit trying to cool down double the square footage we have access to. The problem is that I know I am probably not supposed to have gone in there. I can’t bring this up to my landlord without risk of getting in trouble for it, but at the same time I am immensely frustrated that we may have been swindled out of a ton of money for no reason. What are my options here?

TLDR; Half of the house I rent in is undeveloped and inaccessible with no door in. I entered through the window and found out that the AC I pay for has been cooling down those rooms for 1.5 years, and potentially raising my power bill. Trying to figure out what I can do.