Very effective for cold climate/weather, not so mach for heat.

I did this for the windows on an old 1920’s cabin in BC, the walls and roof cavity had been retrofitted with insulation, leaving the windows as the big heat loss spot during winter. Didn’t fix how cold it go inside during winter completely, but it did bring the unheated temp up a degree or two, which made heating and keeping a temp easier.

Summer, OTOH, it created a heat pocket that radiated more heat inside, so I did a covering for outside with light coloured heavy fabric (forget what I used, but it was from a sailing shop) for the outside.