it is oak stained with a mixture of gray paint and stain- no oil

I am interested in how does the 'radiant heating system under floor' work? Wood fired boiler, solar or gas?

Water is heated and sent through a series on tubes embedded in the concrete. The water is heated with a gas hot water heater

Question regarding the walls, what is the wood species? Is it different species, stained different colors, or just naturally awesome like that?

it is oak that was stained with a mix of gray paint and stain to look like old barn wood