Yes, I like the idea of straw bale buildings, but I seem to have developed a prejudice against them. I'm not sure why; I think because it rains quite a bit in NZ, and there is also quite a bit of wind in the places I'd like to live in (the hills act as lovely wind tunnels), and the combination is not good when the straw innards must be kept dry at all costs. And I wouldn't use a concrete render, since I don't think it's a suitable building material for houses (don't like damp living quarters, and concrete acts as a big wick).

But, really, maintaining the "skin" of the straw bales wouldn't be that much different to other earth buildings. Mud render with a lime top coat should be reasonably weather-resistent. And it'd be possible to get around the issue of straw bale's lack of thermal mass properties (although it's an excellent insulator) by using one of the alternative building methods to construct the internal walls.

Hm, I think you've made me modify my grand plan. :-) Now, the only difficulty that remains is that NZ has a code for earth buildings, but not one for straw bale (although they're looking into that). Which means that you need to apply for a variation to the code to put it up, which involves more engineering approvals, council approvals and general hoops to jump through, thus more money. Hopefully they'll get one sorted out before I actually will be wanting to build (not for 5 years or so, probably).

Thanks for the food for thought!! :-)