In the Two Point University map and put some torches in the dig sites to see how hot they would make those workspaces (turns out, very, very hot). So I took them out of the Dig Sites, and although the Dig Site is back to a normal temperature, the area around the Dig Site itself is left hot. And it is also definitely affecting students and staff that walk past the dig site as their thermal comfort rating goes down when they stand in the vicinity of the Dig Site. 

Below is an image of it happening - before the person went through the red patch, they were on 100% thermal comfort and now it's decreased. There is no heating item in the Site, or outside the site.

Extra note: Selling the Dig Site outright fixes the issue.