These curtains are beautiful!  But as far as being considered thermal, there really is not much to them.  It is the actual curtain, and then the backing is really only pretty white satin.   They do not seem like they will be thermal, and as far as room darkening they block direct sunlight somewhat, but they let quite a bit of light in, and you can see figures through them from outside.  So they are beautiful curtains, and are very pretty for regular curtains.   But if you were looking for warmth or privacy, they are not exactly what I was looking for.