In most jurisdictions the "Egress" requirements are listed in the local "Fire Code". In my jurisdiction the primary egress door for any room which is used as a sleeping room is 32"W x 70" H and the room must have a secondary egress which may be a Window or door with a minimum opening of 24" x 24". If the secondary egress is a window the window sill may be no greater than 32" above the finished floor. When using a door or window as a secondary egress if the lowest portion of the opening is greater than 12' above finished grade it must be provided with a permanently affixed stairway or approved escape ladder.

As I understand the situation, you can vent the space between the rafter insulation (fiberglass, cellulose, etc.) and the underside of the roof sheathing (using baffles) and add soffit vents OR you can spray foam insulation between the rafters and close off the vents. The option you suggest would not meet any building code I am aware of. I either case it would be best to insulate the full length of the rafters rather than the knee walls.

"1st question, since I have bought CBU for the walls but all the how-tos for kerdi have them using it on sheet rock. Im still leaning toward CBU, but figured it was worth asking. " Good instincts to use CBU. For several reasons I recommend you stick with stick with the CBU. Here's a Kerdi over CBU ditty, it might help if you've never used Kerdi before. 2) "2 The ceiling in the shower. Initially, i was going to tile the ceiling, but my wife thinks it would look like a cave...I had several people suggest to me PVC Beadboard. Any other thoughts? " If a beadboard ceiling will fit the style, you can go in that direction. If you want beadboard but want to avoid the sterile look of PVC, how about teak beadboard? Or a teak plank ceiling. Wood can go well with marble/travertine. Then you can always fake wood on the ceiling with wood-look tile. Or go for a lighter look with glass tile on the ceiling, though plain glass can look cold and modern. Of those I listed, I'd consider teak boards. Natural stone and a natural wood? Why not? 3) L/1100 is plenty good for travertine. But you have to consider deflection in two directions; deflection along the length of the joist (your L/1100), and the often overlooked across deflection fo the plywood that spans the joist bays, in your case, across the 19.2" space between the joists. I recommend you consider two layers of plywood (3/4" subfloor and then 1/2" underlayment if able. If not 1/2", then 3/8" minimum. Ditra (or equivalent) over that. Then tile. Large format travertine demands a protective floor beneath it. 4) Your last photo shows a 1/4" thick to 3/4" thick sloped bed of "sandmortar and membrane". I presume "sandmortar" is deck mud? Mud generally requires a 1-1/4" thickness at the drain. You can go thinner, some guys ust an admix and go 1", some push hard to 3/4" thick. . But going to 1/4" thick, it may not provide a durable base to the shower; cracks, etc. Deck mud just doesn't have any structural integrity when placed that thin. Have you considered QuickSlope or one if its derivatives to establish your slope. I mention QS because it pretty much feathers down to nothing. I think it's an 1/8" thick at the drain end, it's honeycomb structure gives the bed structural integrity. which fits your low-profile requirements. Going hybrid? It can be done. But I generally recommend staying within a company's product line and avoiding "hybrid showers" unless the hybrid version has been warranted, ie, Laticrete's Hydroban membrane with Schluter's Kerdi Drain. Enough for now. Got to go. I'll try to check in tomorrow...Oh, and I'm glad I didn't have to do that drywall. Fun fun fun!!

We've converted two attic spaces (same house, opposite ends) to living space, with low ceilings. From my experience, the first thing to do, after determining whether you can safely/legally finish the attic, is to run the electrical wires. To avoid running duct from a furnace/AC, I'd run 220v for a couple of baseboard heaters, and use the portable AC units which sit on the floor and vent through a window. I can see some natural light, so it looks as if you have dormers, which might be fine for egress and the portable AC units. We used foam baffles between the roof and insulation, then sheetrock as usual. If you are not confident about finishing sheetrock, and don't want to pay to have it done, you can tape it, then cover with inexpensive sheet beadboard. I like your floors as they are, but you'd want to seal them, if not paint. Those are much nicer floors than I've ever seen in an unfinished attic. I'm impressed that there are floor boards at all--I've see a lot of attics with a few pieces of plywood laid across the joists to store boxes. Since the knee walls wouldn't be structural, I think you could frame them yourself, with some research, and basic tools. You might as well frame them in, since that space is too low to use as living space, and if you feel confident enough, you can turn the space into recessed storage--shelves or converted dresser/drawers--very convenient if the space will be used as an office or craft room. If you choose the portable AC option, you could even tailor a storage space to the unit(s), for the off-season. Following are pics of some of the kneewall storage in our half-story attic addition. I did most of the work myself, with limited construction experience. (Left the electrical work to the pro.) The white walls, and closet doors, are the sheet beadboard I mentioned above. I also had to work around closet space in adjacent bedrooms, and the old roof supports, which is why the recessed shelves in the first pic are so shallow. If you can find cabinets, drawers, and chests on craigslist, Goodwill, and the Restore, you can keep the cost down--but only if you have more time, than money, to invest in the project. It would be very difficult to estimate the cost. Our neighbor is a master electrician, and we traded him a strip of land that he'd been asking about, to wire the whole addition. We already had all the tools needed. A chop saw/miter saw, set up in the space as I was working, was invaluable. Circular saw for angled cuts on 2x4 framing. Reciprocating saw for cutting existing framing, and a jig saw for small cuts is also useful. Framing and finishing nail guns are convenient, but I don't like using them, so I did all the nailing with a hammer. I love hearing a nail 'sing' as it's being driven into the framing. :) If you have friends or relatives with construction experience, who will do favors or trade skills, then you can keep the cost down. Kneewall storage ideas/google Portable AC units on Amazon