Drywall – How to stop mold growth on greenboard behind the shower wall

Mold needs three (or really four) things to grow: Stagnant air, moisture/humidity, and dim or dark areas with organic 'food'. The solution you're looking for probably involves using a permanent waterproof barrier (either a paint product -- which would be an industrial coating -- or a foundation product) in order to largely remove the humidity from the equation. Those coatings would need to be installed by a professional. As a cheaper and DIY solution, you might also consider 6mil plastic vapor barrier on the back side of the wallboard.

General construction advice for 'general' showers:

In/on the walls:

• use RedGard as a vapor barrier over the cement board
• use paperless or blueboard sheetrock
• use mildew resistant pain
• adequately vent the room with a proper exhaust fan

In the shower construction itself:

• seal all caulk properly
• make sure standing water can't puddle

Now, all that said, I pretty much agree. Showers as they are today aren't really designed as well as they should be IMHO.

For inexpensive solutions, I'm actually a fan of the more modern pre-moulded systems. You can get systems that look quite nice for under $1500 that come in 3 or 4 full-wall sections with gasket seems. I know folks tend to consider them 'cheaper' than a true tiled shower, but I actually find them much more intriguing from an engineering standpoint. They just make more sense to me in a modern home.

For more quirky/unique solutions, I've seen:

• metal sheeting. Corrugated Galvanized sheets, for example. Copper as another.
• all glass
• sealed monolithic concrete (note that concrete is extremely porous so would have to be sealed with something like an epoxy coating)

And...most recently...we stayed at a new hotel a few weeks ago where the shower walls were made out of solid slabs of the same counter-top material as the vanity. It looked really nice actually, I'm guessing it was a Corian like product.