A quest line in my game features the kidnap of someone from 'the hot lands' and taken to an area known as t'he ice hills'.

The person kidnapped requires high temperatures to even survive.

Using technology from the dark ages, how can they keep him above 15c so he doesn't die, but below 20c so the people of the ice hills can speak with him.

I want to refrain from using magic if possible.

So far I can only think of lighting fires in some sort of greenhouse.