A few thoughts
Definitely check the roof seems. I used a tube of dicor to seal them the way they should be. second, pull EVERY hot/cold register and remove (vacuum debris). I also used the real tin foil duct tape to seal the main ducts to the export ducks. I think only 1 of them was adequately installed. This made a HUGH difference in heating and air conditioning. I also "Bullet proffed" the entire TT by replacing screws, gluing wood that was loose, and using silicone adhesive where appropriate. I re-routed most of the plumbing and installed $9.00 water detectors where I could not directly access the pipes such as; near the water heater, under the shower, and near the external shower-the shelf area in the bathroom. One final; there were no washers or putty in the kitchen sink drains. Simply pull them and use plumbers putty...a 5 min job...
I actually love the layout, the large window in the living room, the kitchen but it took me 10 weeks to seal everything and so far, I have had no problems...Best of luck.