A quest line in my game features the kidnap of someone from 'the hot lands' and taken to an area known as 'the ice hills'.

The person kidnapped requires high temperatures to even survive.

Using technology from the dark ages, how can they keep him above $15^o$C ($59^o$F) so he doesn't die, but below $20^o$C ($68^o$F) so the people of the ice hills can speak with him.

I want to refrain from using magic of possible.

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