Window film

indigoblue11

Can anyone recommend a window film to keep the cold out but the heat in? 

I’ve been looking at the 3m this I late but feel like this just reflects the sun and doesn’t keep heat in. 

tacpot12

This is what you need: Insulating Film for Windows, Transparent Glazing Film 4.5m2 (3m x 1.5m) : Amazon.co.uk: DIY & Tools 

It does work, we use it at home on our back door and in our porch. It tends to only last one season though. 

sk2402005

Solar films only really work against solar as it says, it doesnt add any actual insulation, it reflects some of the suns heat away, so that is not what you want.

the film suggested by tacpot12 will do what you want, and it works by trapping the air between the film and the glass, it is as he says fragile.

twopenny

If there's sufficient depth to the frames you can use clingfilm over it so there's a gap between and that does make a difference.

You ever so slightly dampen the frame and stretch it over. Don't cut off the roll until it's on.

Nightmare to put up and it doesn't look so pretty but it does the trick for a pittance. I used it behind nets or just on out of view windows.