In a past life, we've fielded a lot of questions on what the best kind of floor finish is, and it usually goes something like this: "should I use water- or oil-based polyurethane?"
Occasionally, some also wonder if the durability of a "Swedish" epoxy finish outweighs its potentially dangerous offgassing.
If you understand that polyurethane and epoxy finishes are akin to putting a thin layer of cured-in-place plastic over your floor -- imagine shrinkwrapping wood -- then you mind guess that any polyurethane isn't the greenest choice. But what else is out there?
• Wax, like Bioshield #39, is a traditional finish and can come in handy if you like your floors to gleam and shine. (Just be careful, though -- there's a reason they use wax at the bowling alley!) Wax is typically applied over a sealing layer of oil-based finish. Wax usually needs to be buffed with a machine, although it can be done by hand.
• Oil-based finishes. Like wax, oil finishes (not to be confused with oil-based polyurethane) come in a variety of formulations from totally synthetic to 100% natural. Without question, natural finishes are greener, but they take more time to cure, so most contain at least some synthetic dryers. These can be more labor-intensive to apply than wax, but less forgiving than polyurethane: overapplication can be a sticky disaster!
• Bare: yes, you can leave a floor free of finish. Everyday wear and tear will show, but create a kind of patina that can be lovely on its own. The floors will need a good scrubbing with an old-fashioned bristle brush and saddle soap every year or so. But you can be at home with a beautiful floor, no offgassing, and no guilt.
An advantage of all three of the above: we find that most wood just looks better without a plastic coating. And if an oil- or wax-finished floor gets damaged in one spot, that spot usually be sanded and repaired without disturbing the rest of the floor. Compare that to polyurethane, where you'd have to sand everything off, and oil and wax start to seem much more sensible.