How to heat a building?

[werepacman]

Character sleeps inside small building with 6 firewood burning in fireplace.
It is early seedtime. But he always wakes up shivering from cold.

Even at winter spring he could sleep inside the shelter.
What happened with heating building mechanics?
Did forest spirits rose prices for heating apartments?
It seems cheaper to sleep outside.

He wears only rough linen trousers, rough woolen tunic, fur mittens, fur footwear.
No furs on bunk. But building does not keep warmth.

[Tinker]

I do not remember seeing anything about changes in temperature changes in the news file, but you are not wearing many clothes and 6 firewood is a minimal fire. Spruce twigs as bedding will help and closing doors seems to matter, furs more clothes and bigger fires seem the best option.

[Privateer]

Put some furs on his bed and burn some wood for God sake!

tbh firewood is kind of a tool to waste time not a method to warm your home. Put the parent wood item in your fireplace.

[werepacman]

Probably closing doors helped. Spruce twigs is great advice I forgot about this.
By parent wood do you mean burning the whole tree trunk inside the building, is it safe?

Also does sauna keeps temperature better?

I think about ways to avoid repetitive tasks to save time for exploration and don't turn forest into field very quickly. I know people used moss to rise efficiency of building heating.
Also not realistic but you could create self-closing door mechanism with rope and stones or with flexible branches.

[Erkka]

I think placing dried moss in between the logs is automatically simulated in UrW. Another historically used method was to slam clay on the walls. But cabin building in UrW doesn't explicitly mention all these details - it is just assumed that some method is applied based on materials locally available.

I know a person who, in real life, used to live alone in the Finnish woods, and wanting to minimize boring repetitive tasks he also minimized time spent on making firewood. So in the wintertime he maintained indoor temperature of +8 Celsius, for anything warmer would've required spending more time chopping firewood, but the guy preferred to spend more time playing a flute, or crafting tools and clothes etc. But, to do that one has to compensate by always wearing warm clothes, and having a lot of blankets (or furs) on the bed.

It might sound counterintuitive at first, but in real world a sauna building doesn't need to keep temperature as well as a cabin. In a cabin people would like to maintain a temperature in range +8 ... +18 or so, constantly. But a sauna can be heated up to +120 Celsius, and then allow it to cool down, and since no-one lives there when it is not heated, it doesn't matter if the temperature falls below freezing when the sauna is not in use. So, the sauna stove is built differently than the one used to warm a cabin. And the process of heating them is different - a sauna stove can be heated until many of the stones are red-glowing hot. Because water is applied onto the stones, there will also be a lot of moisture in the air, so it is only good that there is good ventilation - no need to tightly insulate every little gap and crack in the log walls.

[JP_Finn]

6 firewood would barely warm up a cabin for few hours in real life.

In game I often push 12 firewoods* in the fireplace, with embers still going after setting porridge or stew cooking. Wake up in the morning pick up the breakfast, push in anywhere from 4 to 12 firewoods*2 in and light it up.

* depends how far below freezing the GUI thermometer is. If you’re still close to bottoming out, I’ll shove in a block with branches to light it up.
*2 as above, colder it is, more wood.

[werepacman]

6 firewood would barely warm up a cabin for few hours in real life

It depends of the size of firewood.

But shelter even has no firewood inside. May be snow and small space helps keep warm temperature.
Or it is temperature fluctuation makes some days at summer colder compared to spring.