I’ve been thinking about this practically my entire life; my favorite daydream.
Ditto floor-to-ceiling library (but with glass doors to keep the dust off), dumbwaiter, passive solar, rainwater and greywater systems, secret room. A secret passage or two. Also, a built-in vacuum cleaner system – we have one in our new house and it is GREAT. And a good dishwasher. Many of my must-haves involve keeping the place clean with minimum effort. Also:
The Clothing Room. This room’s only job is clothes: washing, mending, hanging, folding, closeting, trying on in front of a mirror, etc. You get dressed there. You get undressed there. You do laundry there. Clothing has no excuse to sneak all over the rest of the house and mess it up. It’s on the second floor, and there’s a window that opens on to a reel clothesline, so you can hang your dryables without carting a wet load of fabric outside.
The Tent Bedroom. The bedroom is only big enough for a bed, is above the top “floor” of the rest of the house, and has windows all around and a skylight (all with one-way mirror glass, you perv, and insulating shades for if it’s cold) just like a backpacking tent with the rain-fly taken off. You can stargaze and watch rain falling from bed, panoramically.
**The Bunny-Friendly Kitchen.**One of the lower cabinets is really a flap-door to the outside rabbit run. There’s a drain in the middle of the washable floor for coping with recently adopted buns who aren’t litter-trained yet. It’s open to the living room by way of an island-type half-wall, and the doorway from there to the living room has an easily-handled bunny gate to keep the little nibblers away from my books. Another cupboard space is really a nice safe cuddly place for bunnies to sleep.
Also, a pantry, and dish storage sized to fit actual dishes (instead of, e.g., shelves deep enough for one and a half plates).
The Womb Room. A windowless room the size of a walk-in closet with studio-quality soundproofing and wall-to-wall pillows. You can go in there for five or ten minutes and empty your ears out; alternately, you can practice your primal scream without the neighbors calling 911.
The Sensible Bathroom. Keep the toilet in a separate little niche from the shower, which is separate from the vanity/sink. Bathrooms I’ve seen in San Francisco and London are like that – more than one person can do bathroom things at a time without having multiple bathrooms.
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The Firewood Pass-through. **Next to the woodstove (or fireplace, if you lean that way) there is a little door in the wall especially for moving firewood into the house from the woodpile outside without drizzling sawdust and bark all over everything.
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Storage space actually designed for storage. With shelves, and drawers you can have labels on, like file cabinets, and not in a place that might get flooded. No more damp cardboard boxes on the basement floor. No more searching through six boxes tucked into the crawl space to find what you’re after.
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The Friendly Front Porch. Big enough to sit around with friends or neighbors dropping by, small enough to feel intimate, sheltered from rain and direct sun, with screens if climate demands.