We ran the unit yesterday without a filter at all and the house stayed at 71F through 1pm. At that point the temp rose throughout the afternoon but never exceeded 75F. House was back to 73F by 8:30. This is perfectly acceptable to me as it was very hot with high humidity levels. We have had 4 days of "excessive heat" warnings. I know those of you out west have to be laughing about excessive heat in the 90's-heat index 115 when your temps are at 110-115. What do we do now about a filter? Go to Lowes and purchase some that can be cut to size? The unit has a slot for a 1" filter that is now empty and the box that holds the 5" pleated filter. Which should we use? I will call my installer on Monday, but this is not an emergency and I'm not calling them on a weekend. Thanks for all of your help!