To design the retail showroom at the Real Goods Solar Living Center, we conducted an analysis of the climatic conditions of the inland valley site in Northern California. Several tools helped us to respond to the climatic demands of the site and aided and informed our design work. Heliodon studies were performed at the Pacific Energy Center in San Francisco, California. The Heliodon table helped us quickly simulate solar azimuths and angles throughout the day and year. We used a video camera equipped with a fiber optic lens placed inside the model to film direct sun penetration throughout the day. This "time-lapse" video proved an invaluable tool for study, as well as an effective means of presenting the concept to the Real Goods staff, effectively bringing the building to life during the design process. This analysis gave us the information we needed to shape and size the southern overhangs, sunshades and awnings. The building welcomes solar gain in the Winter and Spring but keeps it out in the Summer and Fall. Employees can tune the movable awnings to seasonal variations and can fold the insulated translucent interior light shelves against the low-e glazing on Winter nights to greatly reduce heat loss. The straw bale walls, 23-inch (58cm) wide with 3- to 4-inch (8-10cm) of PISE gun-earth on each side, provide an R-value of 35 as well as significant thermal mass. These walls, in combination with the thermal mass in the floor and columns, moderate outdoor temperature swings throughout the day and year. Consultants, including the Pacific Energy Center, have all concluded that "you can't have too much mass" (so long as it's within the insulation envelope - especially in more severe climates). We provided an "Operator's Manual" to the Real Goods store staff to teach them how to properly tune the building for comfort, i.e. when to open or close the clerestories, etc. This could have all been automated, but we chose to let the staff interact with the building to afford them the opportunity to learn about and have control of their environment. We selected the curved roof not so much for its relationship to the plan as for its qualities in helping distribute daylight throughout the showroom. We built a large-scale section of one of the bays and tested several options for even distribution of daylight in the Sky Dome at the University of California at (UC) Berkeley. Seven Licor photometric sensors wired to a Campbell Scientific datalogger produced daylight factor graphs. Our seventh test, featuring highly reflective film on a tilted shelf, produced the most even distribution of daylight. We mounted reflective scoops above the trellis on pulleys for adjusting the angle seasonally. The system works so well that artificial lighting is rarely used. Substantial breezes from the Northwest inundate the Hopland Valley daily. Based on the results of tests at the Boundary Layer Wind Tunnel (also at UC Berkeley), we used clerestory windows at the roofs, which step to the east, to naturally ventilate the showroom. A "Bernoulli" effect creates a pocket of low-pressure that draws warm air from the high ceiling out of the manually operated windows. The building draws fresh air from the shaded north side, and solar-powered evaporative coolers further cool the air when necessary on the hottest summer days. The building is flushed each cool summer night, storing "coolth" in the floor, walls and columns. The building works incredibly well. On 113°F summer days, the building stays naturally cool (in the low 70s) inside; and during the cold winter months, it is naturally cozy and warm. The building has no mechanical heating or cooling. Climate responsive design and material selection keep the interior temperature comfortable and stable throughout the year. People can't believe it works until they walk in the door - on a 100°F day it will be between 70 to 75°F in the showroom. These strategies also save energy. Overall, the building uses 80% less energy than a conventional building of similar size. And nearly 80% of this energy is generated on site with a 10 kilowatt solar electric system and 3 kilowatt wind energy system, saving in excess of 50,000 pounds of CO2 annually. The photovoltaic system is intertied to the local energy company's power grid which enables Real Goods to give surplus energy to them and use their grid as a storage system. Constructing a building that is curved both in plan and section for close to $150/ sq. ft. in Northern California was no small challenge. We found, however, that simple and inexpensive solutions are often the most environmentally sound. The curved north walls were easy to build with straw bales. The bale walls have more than three times the insulation value of a typical insulated framed wall. The bales are covered with a gunite-like application of soil-cement which includes native red-rock soil for a natural color finish. Generous overhangs protect the walls and provide shading. The curved glu-lams of certified sustainably harvested Douglas Fir are both elegant - we've left them exposed - and ecological. The beams were harvested, milled and manufactured within 40 miles (64 km) of the site. We reused the 2-inch x 8-inch (5cm x 20cm) concrete formboards at the tops of the bale walls and in the roof overhangs. The trellis structure is made of steel cable in tension and reclaimed redwood from dismantled lumber mills. Other alternative products we used include: Meadowood (pressed strawboard), radiant barriers and ventilated cavity walls, high-efficiency dimmable fluorescents, hemp sunshades and awnings and old toilet tank covers used as tiles in the restrooms. Heliodon testing of the Real Goods Solar Living Center. Spraying PISE on the straw bales walls of the Real Goods Solar Living Center.
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