Americans who grew up in the 1950s or early 60s (that includes me) remember living in a house with one bathroom. There was usually someone standing outside the door yelling, “Hurry up!”

These days, most Americans live in (or aspire to live in) a house with two or more bathrooms. My guess is that we’re never going to return to the bathroom standards of the 1950s; two-bathroom houses are probably here to stay.

If you’re designing a green home, you know that a guiding principle of green design is, “Small homes have a lower environmental impact than big homes.” It’s a good idea to keep that principle in mind when you decide (a) how many bathrooms your home needs, and (b) how big each bathroom should be.

You may need fewer bathrooms than you think. Many families will find it easy to live in a house with one full bathroom and one half bathroom (that is, a room with a toilet and a lavatory).

In praise of the small bathroom

For me, the main reason that small bathrooms make so much sense is that bathrooms need to be cleaned regularly. Smaller bathrooms are easier to clean.

Which rooms deserve extra square feet? I believe that the rooms where we spend the most hours per day — usually the kitchen and the living room — should be spacious and delightful. On the other hand, the rooms where we don’t spend much time — the bathroom and closets — should be as small as possible. (Bedrooms, too, should be as small as possible, because most of the time that we spend there, we are unconscious.)

A short vocabulary lesson

In the house I grew up in, everyone in the family brushed their teeth at “the bathroom sink.” These days, there is no…