Solid Fuel Fireplaces

If a house has a gas furnace natural draft water heater and a fireplace with solid fuel fire, this type of house is ita

a nice warm house

Well, if its above ground, it does not look like a model Cave.

I do not know how this technique is, but you do not need electricity to exist in this environment.

Well - I'm not really sure what you call home, but I think what they want is that the house needs a "leak" outside air in the house or provide some type of make-up air. All appliances above receive combustion air from the surrounding space (s) rather than being sealed combustion or direct vent, which draw air outside.