Comfort is not something we moderns invented. The Abbey of Reichenau in southern Germany had central heating already in the 9th century.

They used a Roman invention, a hypocaust floor, with a 90% fuel efficiency rating. Far far above that of any modern central heating system.

Here is a Roman example from Austria. A fire would be lit and a draft would circulate the hot air throughout, leaving little heat to escape.

Traditional heating systems made use of low value fuel (twigs, branches): each system was designed to fit the type of room it would heat.

The open fire in the center of the room was perfect for thatched roof houses. The smoke would rise up and "cure" the roof, drying it out.

In this way the heating system worked with the building material prolonging the life of both. We still have roofs from the 14th century.

When houses got rigid roofs, chimneys had to be invented and the fire would have to "housed", the fireplace allowed for new ways of cooking.

Open fireplaces are cozy but have a low fuel efficiency: 5-12%. They wasted fuel and 14th c. Europe was hit by energy crises, deforestation.

With open fireplaces most of the heat leaves via the chimney, what is worse, it draws the hot air from the room pulling in cold outside air.