A/C cycling in and out

My fiance and I thought we had entirely lucked out with our first house. We were very picky, as we were trying to avoid buying a major fixer upper! We still had a small budget that we could not go over. When we found a house built in the last few years that was just within our price range, we thought we had won the lottery. The roof is in excellent shape, the plumbing was still sound, and the house had begun to settle but presented no major complications. The only complications looked minor–window gaskets, door sealing, all the little things we expected in a house that had been owned by the same family for many years. After our first week in the house, we got our first utility bill–we could not believe how high it was! We hadn’t even noticed the A/C was cycling so much! But come to think of it, the HVAC was never entirely quiet. We called a HVAC service provider to come out and look over system, and it doesn’t look good. Though we changed the air filter our first morning in the house, there was already gross buildup in the HVAC duct from the previous owner. Not only is the HVAC duct dirty, but there are huge gaps in the system that need to be repaired. Now we have to pay for an intensive duct sealing and duct cleaning. So much for buying a new house and avoiding major complications! If we had bought an older home, we could have bought a house without forced air.