How can I insultate my patio doors?

[BoBoo]

I'd like to improve the insulation in our house but feel like the patio doors are a huge potential source of heat loss. We will still need to use the doors throughout the winter to access the garden and they have a cat door in them so cannot cover completely.

Has anyone used anything like this window film? I am sceptical.

[PigletJohn]

these are double-glazed, I suppose? Plastic or aluminium? Hinged or sliding? Is there a draught in the middle or the closing edge?

Window film is useful on old single-glazed windows but liable to damage if you keep going through the door.

You need a large thick lined curtain. For such a big window, a cord-operated set is best.

[PigletJohn]

correction
the stuff in the ad you link is stuck to the glass and is approximately useless for keeping heat in.

[BoBoo]

I suspected as much. They're plastic, double glazed, hinged.

[PigletJohn]

then check the draught-proofing round all the opening edges. It will be factory fitted so if not working call in your local patio door wo/man (there will be one) to adjust.

Otherwise get those curtains.

A cat can walk round curtains, though not (easily) a venetian blind, which is a useful second layer.

[Artistic]

We had a similar problem. I don't suspect we had much leakage but the patio doors were large & made the room cold. We installed thick curtains from Hilarys (no necessary) & had them done with thermal lining. Makes a huge difference to the room & the entire ground floor. The area is definitely warmer & the room is equally warm near the patio door as it is further away. Totally solved the problem!