AK's idea seemed cool, I did some googling. There are companies in NZ and UK doing it. Dow tried a version using virgin PET earlier in the decde as did another company using recycled content but they were discontinued, apparently they couldn't get enough sales at the price point required. None of them used a fire retardant, apparently it does pass flamespread and smoke developed without anything. One note I saw said that the fiber retreats from flame faster than it can ignite, yeah I'm a little skeptical too. The concept is cool, my uncle worked on the development of those fibers back in the 70's, I had a bag full of some early test material that he gave me to make camping gear.

I think you nailed one of the main problems with any discussion of sustainability Dave, basically we are at something like 7 or 8 times the number of people that this planet can actually support sustainably. I worry not for the planet, just as when rabbits overpopulate, it will solve that problem if we do not.

Look up NatureWorks Ingeo fiber, that is neat looking stuff. They are using plant based feedstocks to create a plastic that can be used pretty much in the same applications as oil based plastics. Rather than 600 million year old sequestered carbon they are using annually replenished feedstock that is absorbing CO2 rather than creating it. Also ran across a company experimenting with making an insulation board out of mushroom mycelium, they grow the board or bricks, pretty neat.

For the life of me, I can't figure out why polyester insulation, made from recycled plastic bottles, is not becoming more prevalent...
...usually every winter I end up with at least one dog bed getting left out in the backyard under the trees....I generally can't move them until mid-may or sometimes even June because they are frozen on top of a SOLID block of ice until then...that's good insulation! ....and water doesn't seem to bother it at all....

The complex roof algorithm seems to be fairly robust thus far, I haven't been able to break it just yet. However as I am contemplating how to make it so that each roof plane is adjustable (variable pitch) it is quickly becoming apparent that such a feature would become very complicated.

The issue really is a situation where you have a particular roof plane that you want to adjust.  You then change its pitch (assuming all other pitches are left the same) and the roof gets recalculated.  In certain situations that roof plane may then merge with another roof plane.  If that happens then one of the two roof planes is absorbed by the other (both pitches must be equal of course).

The difficulty seems to arise in the tracking of each roof plane and the custom pitch assigned to it.  The number of roof planes can be variable.  The ability to edit each roof plane will need to an "on the fly" sort of tool which allows the user to adjust only one roof plane at a time and then recalc the entire roof to re-determine the shape of the roof and hence how many and where its new roof planes actually are.

The easiest way to store this information, in my option. is to maintain the roof solid group (on a separate hidden layer).  From this solid the roof planes can quickly be ascertained as well as the outline or footprint of the roof.  I'm still thinking this one through as you can probably tell. 

Initially the roof will be drawn with one overhang and one pitch.  Where the edit menu can take it from there is where it potentially becomes quite complicated.

Consider a complex roof like the one below:



I can see that the framing can be accomplished with some basic rules/logic however non-orthogonal roof outlines will probably require some additional logic.

Jason,  the plan is to do everything but the spray foam insulation myself. You were right about the rainy days, but it looks like the sun may be returning. Still need to backfill and I've been keeping busy emptying the moving trailer into the shipping container. Hopefully the weather holds. Thanks for following along.

I've decided to put the drip edge on hold for just a bit and focus on the secondary roof module.

There is really two ways to handle this.  You can either start with a primary roof and then add secondary roofs that tie into it.  Or you can allow the user to pick the building outline (any polygon) and utilize a straight skeleton algorithm to compute the roof planes.  There are some pros and cons (limitations) to each method.

Obviously with the straight skeleton method one would assume that the fascia lines up all the way around the roof so it doesn't lend itself to secondary roofs like dormers that may be positioned up on the roof.

However, the straight skeleton allows for some really complicated scenarios that you just cannot achieve with a secondary roof methodology.

A few months ago I was trying to come up with a robust straight skeleton algorithm and somehow it defeated me.  This morning I took a slightly different approach and I now think I've finally solved it:

Step 1:




Step 2:




Step 3:




Step 4:



Once I have the roof "solid" I can then easily pull out the edges that represent the hips, ridges, valleys and flying hips.  From there it is just a matter of some tedious logic to detect whether to frame a common, hip jack, valley jack or cripple jack (hip/valley jack).

Of course the devil is in the details but I now think I have a path forward for complex roofs, this is major breakthrough.