Although the air conditioner was at a minimum level of insulation and leakiness, I then moved to sealing the aire leaks in the attic.
Basicaly, there are various holes and gaps in the attic floor where, air can come from inside the house and flow to the atic and then outside. these holes should be closed up stopping the natural draft from moving conditioned air to the outside. It has the additional effect of reducing moisture in the attic furing the winder when warm, moist air from inside meets cold dry air in the attic.
The process is grueling and messy. Basically, everywhere the top of a wall meets the sheetrock (in the attic), there is a potential gap between them. Because the interior walls are not insulated, thee gap creates a nice way for air to leave the house. Specifically, through outlets under baseboards the air can move. A 1/16th inch gap along the baseboard of a 8 foot long wall is like having a hole in the wall the size of a nickel. A few outleft can add up to another nickel. Based on normal variations in plane of the floor and baseboards as well as the design of outlets, you can have a few dquare inch hole equivalent hole in each room of your house. Keep in ming, that the gaps can also ectend to other floors of the house.
Wires and Pipes.
Everywhere a wire goes into a wall, a hole needs to be drilled. These holes are typically not closed and make a nice exit for air into the attic. Pipes can have a few square inches of unfilled gaps around their perimeter. All of this needs to be sealed.
Light Fixtures.
Underneath a ceiling light is an electrical box. This box is mounted over a hole. Depending on how it is installed, the gaps around the hole can be significant. Also, within the body of the electrical box are often various screw holes, and other holes. All of this is a nice way for air to escape into the attic.
Soffits:
A soffit is basically a protruding box into the living space in your home. Although my house does not have any soffits, my previous home did and, the buiders left the entire top of that soffit (within the attic) open. There was a 2 foot by 4 foot hole from the top of the soffit into the attic. Besides being uninsulated and basically a 2×4 foot uninsulated surface in the house, this opening had about 6 lights mounted on the face of the soffit, these lights all had holes that fed into the attic. I’m guessing but perhaps 10% of the energy loss of the house could be due to this one structure.