 Change it out. Change it out. The flat filter is 30 days. So that's one way you can be more efficient and make yourself more comfortable in your home. The other one is as old as the moon. Pull the shades. Pull the shades down. Even if you've got the best of windows, low e-glass and all that stuff, and diminishes solar heat gain, great numbers, pulling the shades down just helps a little bit more.