I live in a manufactured home set on a slope, built circa 1995. The builder installed all the supply ductwork underneath the house, exposed to outside air, and it's all flex. The return is indoors just above the AHU. The heat in the house is uneven, it's several degrees warmer (or cooler in the summer) in the rooms closest to the AHU.
I have a feeling that a lot of heat is lost on the ductwork along the way, and possibly have leaks in it due to small animals as we live out in the country. I'm trying to think of ways this could be improved and was wondering if (after I patch any holes and looking for obstructions) there is a way to insulate flex ducts to reduce the amount of heat transferred to (or from) the outside air. If this is too DIY just let me know. Not planning on touching the equipment itself.