It is double skinned Jean, except in the Cone ends where it is single.
But that is a very small amount of living space inside the tent that is single skinned, and as such it works well.

Check with Mr Sloman on his opinion of Warmlites.

There is also very good ventilation if you keep the vents open,
and they have mesh to stop invading beasties.

I have actually cooked (gas) inside the tent, with the porch zipped shut.
Mind you, it was pretty horrid outside.

The front vestibule is huge, and with one person, you can get all your gear inside easily, even when wet. Indeed, for 1 it is a bit of a palace.

I can testify to that, it did 2 Challenges with me.

For 2 people it would be more of a comfy fit, and I suspect a bit more condensation.

I can send you some more pictures of the inside if necessary showing the dimensions.