I'm having a flooring dilemma and I am trying to find the perfect flooring for hydronic in-floor heat. I like the idea of doing slate for a whole-house application but I wonder how eco-friendly it is.

This is one of those tricky areas of sustainability and green design.

As a whole compared to many materials, it could be considered eco-friendly in that it doesn't off gas, it doesn't have weird chemicals that might leech into the environment and it can last almost indefinitely. In certain applications it is recyclable.

but....

It is not a renewable resource.

How is slate mined? How much pollution does creating that slate tile make? What is the inherent energy within each slate tile? What effects does the mining for slate have on the environment? Where is the slate from? How much fuel does it take to get the slate from the mine or quarry to your door?

Like concrete, it is initially terrible for the environment, but over time, the fact that it is a lasting material, it gains eco-friendliness.

So...

I would have to say no. However, I love slate tile floors and if you think that the floor is going to be around for the next 20 years, then I could see that it might be considered an environmentally friendly application. That said, if I could afford them, I would probably put them in my own house.

Also try and look at the project holistically rather than at each individual part.