ok yan isara if 100% when you use it naka A/C ka, pero if you want the option to open the windows, but regulate the light coming in consider:
a. install blinds + thick blackout curtains sa loop ng HT room, and putting tall plants sa labas to regulate light outdoors.
b. fabric borders na detachable, if you want hooks lang sa taas, slim foam backed with 1/4" or 1/8" covered in custom fabric of the color of your choosing,
c. tony (trod93) makes really awesome diffusers, and aesthetically pleasing with the right varnish tone it will diffuse and accent that board for your windows, if you want it tanggalable or foldable, baka pede 4 bay split, or piano hinged para you can still open the windows
click pix to his thread