goku2100

You guys have only a faint idea about the benefits of using products with a low U-value. You want a low u-value on anything you're insulating so that you slow down the 'equalization' of energy between the two areas. I.e. If you want to keep something cool and it's hot outside, you want a low U-value. If you want to keep something hot and it's cool outside, you want a low U-value. Whether insulating a thermos, your car or your house, the lower the u-value the better... U-value 99% of the time works in both directions, it is NOT limited to keeping the heat in but could be used to keep it out. You are correct you cannot 'reflect cold' but you can reflect or retard heat transmission. Now you say, well it's summer time, 105F outside, why would I care about a low u-value film when the 20% heat rejecting film works just fine? Because while that tint will retard direct radiation from the sun, it will have no effect on low frequency radiation, such as high air temperatures. So it will block the sun shining through but if it's 9PM and the sun ain't shining, a tint with a high u-value will underperform the film with a low u-value. I am aware that the film touts its benefits by suggesting it reflects the heat back into the room, but the properties for the low U-value rated films are both for Winter & Summer so it's pretty clear the u-value works both ways.