Thank you, Brian, for your input. I should have included all my means of maintaining thermal comfort. Here is a list of the systems that would be in place along with other conservation strategies.
-R-90 roof with summer ventilation and reflective coating to control "attic" temperature.
-30" rammed earth interior/exterior walls to average out diurnal wall temps and provide lots of thermal mass to average out temps over longer periods, say 3-5 days. Most extreme heat and cold spells only last a few days around here. I'm considering increasing internal(isolated) wall thickness to 36"-48".
-Thermally isolated floor/deep earth thermal conduit. The average floor temperature should stay around 75 degrees and would effectively provide a huge thermal mass.
-Night purging to further bring down average interior summer temps. I am thinking of making use of a thermal chimney with temperature actuated shutters.
-Ceiling fans all tied to a thermostat which will activate in the hopefully rare event that temps exceed 80 degrees in summer. Based on my estimates this would only be necessary in the late afternoon/evening for less than a month each year.
-Solar gain to raise wintertime average temps. Slightly over-sized windows to store extra energy to maintain thermal comfort in cold spells. In the event of overheating the ventilation system would activate in order to maintain thermal comfort.
-Efficient appliances and lighting to reduce internal heat loads and electricity use.
-Efficient multi-paned windows to reduce heat loss and gain. Minimize north/east/west glazing.
-Minimal air infiltration with controlled and appropriately timed fresh air ventilation.
-Exterior shading using deciduous trees to minimize unwanted solar gain on the building envelope.
-Skylighting to provide natural light and further reduce internal heat loads due to electric lighting. According to studies on existing structures electrical lighting adds to internal heat loads much more than skylighting.
-Low maintenance structure/systems. I was hoping not to have to insulate the exterior walls. I like the looks of rammed earth and want to reduce the construction workload and eliminate exterior maintenance. Insulating and plastering the exterior would be expensive and time-consuming.
-No energy intensive thermal control systems.
-PV system.
-Water harvesting.
-Grey water.
-Xeriscape landscaping.
-Gardens, orchards, permaculture. Growing ones own food saves lots of money and resources and enhances health.
-Solar hot water combined with point-of-use on-demand water heaters.
Average high/low/median mid-summer air temps are 100/76/88. So average wall temp should be about 88 degrees. Then if you average wall temp with floor temp(about 75 degrees) you come up with 81.5 degrees. Wall area is 1200ft2 and floor area is 1000ft2 so it should average out fairly well. Then you take that average and consider the night purging you should wind up slightly under 80 degrees. I think with such a high level of insulation combined with attic ventilation the roof can almost be taken out of the equation. So add a few degrees for minimal external solar gain and internal heat loads it seems you might wind up around 82 degrees average during the peak of summer, probably for less than 30 days. That should be comfortable with a slight breeze from the ceiling fans. Also, there is an interesting phenomenon in breathable earthen walls where they release more moisture with increasing temps, resulting in a slight evaporative cooling effect.
Here is a very interesting and informative page about human thermal comfort by the way:
http://sustainabilityworkshop.autodesk.com/buildings/human-thermal-comfort.
Feel free to give me a reality check if you still feel I'm not taking enough into consideration. Any other ideas you have for reducing general resource usage would be welcome. I wish ground temps here were lower than they are, it would make everything much less complicated.
