John61 wrote:

My new house has a few big windows facing southwest, taking much sun heat in
the afternoon. Have to keep the heat pump working till after midnight to
cool down.

I went to HomeDepot and hoped could find some kind of window film that can
block sun heat - something like we put on minivan window glass. But there
are only some small packs of decorative films available there. Need some
advice on this.

Thanks.

I noticed a good deal of solar gain in the afternoon from one big window
in my house. The window has mini-blinds that I pretty much never open
anyway, so for the heck of it I just taped a mylar "space blanket" over
the window. The afternoon temp near the window dropped dramatically,
reducing the overall A/C load, and with the mini-blinds closed anyway,
you can't see the space blanket from the outside. There is another
window in the room that doesn't get blasted by the sun so the room still
gets plenty of natural light.