I'm not filming him all day so I don't think it would contribute much to the overheating, but it was more about whether opening the curtain and having light coming from the side would work better than the light coming from above (house light) when filming. Certainly having him in direct sunlight all day wouldn't be good. It wouldn't have been my first choice by far, but compared to how it looks otherwise, it was worth a shot. Probably wouldn't fix it though. Saw suggestions of some kind of polarising filter though so I'll have to look at that and see if I can put something like that in front of the webcam and see if that makes a difference.