Housing in rural mountainous often more expensive caused by high transport price, difficult terrain and construction condition. => Figure out nature material, cost effective factory, store... Local material reuse. Fireplace, chimney design. It is very rarely a house with chimney in Vietnam. I think some home it is useful, at least in northern area where climate more cooler. It not only used for warming but also keep moisture away? Firewood burn also clean air? Keep an eye on safety since fireplace could lead to structure damage, fire... Study existing design, best practice, safety advice to apply.