Most manufactured homes are set up with flex ducts from a package unit outside. Those flex ducts can be easily damaged by critters. mostly rats and cats ( they like air conditioning where they live too). A good thing about the package units are that their tops can be easily removed to clean the indoor coil.
If a room is pressurized from air coming in but has no easy path back to be recirculated the pressurized room will blow air out any leaks in the envelope. Air will be made up through other leaks nearer the return. The solution is to open interior doors or pay for duct upgrade.
When a house is unoccupied and air conditioned the interior doors should be left open. This is irrelevant if there is a return duct in every room. These are not common though required by code for new construcion for about 5 years.
Ceiling Fans & Recessed Lights
Ceiling fans are okay if they are turned off when one leaves the room. I have been called by more than one customer to check the central air (who have been advised by an energy expert from the power company to turn off the ceiling fans when they leave the room) and they are on in all those unoccupied rooms. I hear that it uses $5 ea per month to run them constantly. Also, the air circulating by an uninsulated surface like a window can add heat gain in summer. Recessed lights can be leaky.
Clothes dryers exhaust about 150 cfm of air...more than most bathroom or kitchen exhausts. If installed in a conditioned space that is a lot of conditioned air leaving the house. A solution includes opening a window in the laundry room if available. This lets outdoor air get pulled into the dryer and exhausted outdoors. Without opening the window the comfortable house air will be exhausted. The slight vacuum created will cause outdoor air to leak in the house, unfiltered and create a load on the air conditioning. If the dryer vent on the outside is near the outdoor unit of a/c the lint from the dryer will restrict airflow at the a/c inlet raising elec use of the a/c.
A tree to shade the outdoor unit can be good for energy savings. Leaves may need to be cleaned out from inside the outdoor unit and raked away from the coil inlet. bushes can inhibit inlet air if not cut back.