They seem to. Here are some comments:
“It cut the Houston Texas heat in the bedroom 8 eight degrees from 80 to 72 in the early morning sunrise, you did not wake up early, because you were hot.”
“We live on a lake and the wind gets rather rough in the winter in our lakeside sunroom. These solved my problems with the cold in a room with windows floor to ceiling. It has also been really hot this summer and the curtains have reflected the >100 degree temps really well.”
“I have truly enjoyed the solar curtains and my engery bill hs decreased.”
“These solor curtains have made a world of difference. Keeps the sun/heat out making the kitchen about 10 degrees cooler.”
Source