This group has been an extremely valuable source of information for me in the past years, so I thought I'd post another in a very infrequent series of questions. Thanks in advance for any and all advice.
I am building (well, I am the developer, which is to say I am having built) a small commercial building with 16,000 sq ft of office and light manufacturing space. The building is in an area of N. California with quite mild weather all year 'round. We are trying to make this a "sustainable" building; that is, optimizing the building's energy use, water consumption, indoor air quality, and so forth.
We're specifying a mix of wood and other materials (stucco and/or metal siding, TBD) for the exterior skin of the building. Because I'm paying for the construction but may also own the building for years, when picking a wood species for the siding I need to take into account not just installation cost and the environmental factors but also the cost of ongoing maintenance.
My preference would be to use a wood species that requires no finishing at all. This will lower the nonrecurring and recurring costs, reduce the amount of chemicals consumed, and require no long term maintenance hassle. I understand that any wood left untreated will weather to gray or silver over time. I have not found many species that can be treated (or not treated, as the case may be) in this way: teak, ipe, manchiche, perhaps sinker cypress. Of these, I am seeing reclaimed teak quoted over $20/bf (insane), sinker cypress $8-10/bf, and I don't have pricing on ipe or manchiche yet. For comparison purposes, three-coat stucco and paint is about $5/sq ft (more or less equivalent to a bf in this case) installed.
Treating with Cetol is of course an option, though not my preference.
So the question is, based on your experience, what is the best choice? Can I really get away with not treating *any* of these woods or is that asking for trouble? What other woods should I be considering (my local hardwood dealer is recommending jarrah)? Got sources for good reclaimed, certified, or otherwise sustainably harvested lumber?