In 4th edition WGRE there was a spell, Heating the Frigid hall. It was a relatively low level spell to make a large room comfortable temperature. I am curious how people would do it in 5th edition. How large of a fire is needed for it to determine magnitude.
CrIg (base 2, +1 touch, +2 sun, +2 room) 15 to warm a room i would say.
The "base individual" for Ignem is "a large campfire" or "fire in the hearth of a great hall" - so that should do it.
However, I've been in great halls that are "heated" by a fire - it doesn't work as well as it might. Better than nothing, by far, but hardly "warm", depending.
Iirc, Heating The Frigid Hall "warmed the room", it did not create a magical fire that then did the job, tho' it's been a while since I've referred to the details of that spell.
I'll go with ExarKun on this one, only creo spells that actually create things need to be target ind or group. This spell heats something that already exists so it can have a room target.
I don't think the Hound is opposed to ExaKun's solution, just offering the typical Flambeau solution. Instead of heating the room itself, put [color=red]A FIRE! (sigh, 
) in the room and you'll get warmer, possibly very much so 
.