Depends on the density of the knit, the thickness of the fabric, the cut and style of the outfit(ie, length of sleeves, type of cuff, etc), and stuff like that. All things equal, though, loose is warmer than tight.

This is bumuming relatively low humidity on a cold day, of course. On a hot day with high humidity, tight fabric might end up sweaty or damp just from the air and stick to you and feel more hot.

I’ve voted “Don’t know” due to lack of information.