I take it the windows are not tinted. If they are there is a possibility of overheating them if the foil is placed inside the windows. This has been discussed previously; I think on this Forum
Also, get a decent size, QUIET circulating fan to help move the air around.
X2 to leave the A/C on all day/night so it doesn't have to cool all the furniture, walls, etc. every time it is turned on.
If things continue bad after all of the good suggestions get a Sunshield tarp and throw it over the roof with silver side up and with cutouts for the vents and A/C. It will reflect the sun and the space between it and the roof will act as additional insulation.
2003 SunnyBrook 27FKS
2011 3/4 T Chevrolet Suburban
One wife, two bikes (both Electric Schwinn's with motor assist)
There is a point to this topic that sunkatcher was pointing to but did not explain 100%. IF you have single pane windows, placing reflective foil or anything else is a way to go.
If you have double pane/insulated windows, you are REALLY taking chances of overheating the seals and the end result is fogged windows. I allowed my wife to talk me into the MCD shades with the sunscreen on the inside. Mind you they are not tight against the windows. I had windows in the direct sun in Tallahassee and with the sun shades down the temperature of the window and frames was 145 degrees F.
I went to Lowes and purchased sunscreen material then made OUTSIDE covers for the windows in the sun. The temps dropped to 85 degrees within minutes. I HATE THE OUTSIDE COVERS but they do shield the insulated windows from the direct sun.
If you were to call the manufacturers of the insulated windows in your home you will find most advise against films etc. They will void the warranty.
If of course you have single pane windows you can do anything you want. Hope this clarifies a bit more.