I have 2 wood frame greenhouses. The smallest one is 14' x 18' and the larger one is 23' x 26'. I also have two 16' x 96' hoop houses. The roof and lower sides are covered with corrigated fiberglass. They both have storm windows covering the entire center of the sidewalls. I use an attic type fan with a thermostat and louvers to ventilate. I usually wrap the outside in 6 mil plastic during the winter and the fan turns on automatically if the temp gets to high. They are heated with 30,000 BTU ventless propane heaters. We recently moved to a new location and I definately will be using the double wall polycarbonate to cover the roof and sidewalls on the new greenhouses. I still plan to have windows that open. I have seen advertisements for a double wall polycarbonate which comes in rolls that can be used on hoop houses etc. I plan to check this product out for covering the tops of the hoophouses. There are images of all of the buildings on my web site (Link Below)under the Greenhouse menu. The larger one has a design flaw - the roof is to flat and condensation drips from the roof about half way down instead of flowing to the sidewall gutter. Here is a link that might be useful: The Flower Lady's Garden

Albeit a different design, I have a doorless shower that opens right into the master bathroom, without a snail or barrier entry. Because our home is overall well-insulated and warm in the winter, I've not had a problem with the shower being drafty or cold, and most of the water stays inside the shower (we have a rain-type showerhead, which controls the water spray). Some water escapes onto the teak bath mat, and onto the tile floor, but that's why we have a tile floor. I did hedge my bets in building this shower -- if we'd found that it was cold/drafty/splashy, we could install a door. However, after 18 months, we've not found it necessary. And the added bonus of having no door is that the shower dries quickly and we've had no problem whatsoever with mold or mildew, as we did with the previous (closed) shower. If I were considering the design you're showing, I would perhaps extend the half wall and glass a little further, because that particular design looks like it might be a bit more splashy than you might want. (Sorry I don't have a better photo; the bathroom is not large enough to get a long view of the shower.)

I recommend a rainhead as a secondary head, but I'd never advocate a rainhead as the only head in a shower. I figure showers are getting "large" when they get to 42" and larger. For the shower depicted, with a door I'd advocate putting the supply valves on the sink wall. If you reversed the swing of the door then I'd say put them on the tub wall. That way you can open the door and turn on the shower valve without having to step in the shower. With doorless, the supply valves could go on either the sink or the tub wall. If just using a wall mounted standard head, for minimal overspray I'd recommend the head on the exterior wall. I'm not sure where you live (freezing climate or not) but I'm in the northeast where I don't like to bury water supply pipes in exterior walls, even with foam behind the wall and using 2x6 construction. You could surface mount them as an option. If the exterior wall is not an option, then the "bottom" wall would be my next choice, offset slightly towards the exterior wall...essentially in line with the floor drain as depicted. If this is a one-person shower then I'd do a through-the-ceiling rainhead, with the head centered over the floor drain. With no door it's likely you'll get a little overspray out the doorway, but nothing significant unless you're overly enthusiastic in the shower. And no, I'm not going to define "overly enthusiastic". lol You could give it a shot as a doorless setup and add a door later if things don't work out.

Just an aside. We had spotting/rime/etc. problems in our bath/shower/dishwasher/sinks for years due to the local hard water. My wife used to change the shower curtain liners about once a year due to the buildups and slimy feel. We moved into our current house, which had a water softener installed, but that was inoperable. I replaced it and most of those water problems went away. In fact, the build up of deposits on the inside of the stainless steel dish washer have disappeared. I understand the draw of a doorless shower, but for those who do not have the room, the softener can substantially reduce deposits, reduce the amount of detergents needed, make you feel cleaner, and help your water heater last longer. Disclaimer---I do not now and have never sold water softeners. And have no stock in a company that does. :-)