By Graham Carter, Prerna Jain, & Jeff Hou November 1996 Department of Architecture University of California at Berkeley Summary of Results: As a showcase for environmental consciousness and ecological design, the Showroom at the Real Goods Solar Living Center has incorporated various energy-conserving passive environmental control strategies, such as night time ventilation, thermal mass, evaporative cooling, stack effect and passive solar heating. Three months after the June 1996 opening of the showroom, located in Hopland California, the showroom was visited by a group of UC Berkeley architecture students. One of the teams looked at physical performance of the showroom. Temperature data collected over a 10 day period combined with occupant surveys, phone interviews and energy simulation provided insight into the questions of interest. In summary, the findings of the study were: The evaporative coolers were not used during overheated periods due to discomfort created by high humidity. The high humidity is largely a result of moisture exhaled by the showroom's occupants. The straw bale walls are working as thermal mass. The core of the wall has approximately a 12 hour lag with the outdoor ambient temperature. The inside surface temperature of the wall, had a 2 hour lag in relation to the peak interior space temperature. Furthermore, the inside surface temperature of the wall was on average 3°C (5.4°F) lower than the interior air temperature thus providing some radiant cooling. The straw bale wall mass is provided by the PISE while the insulation is provided by the straw bales. The operable windows, clerestory windows, and doors are very effective at ventilating the showroom. The high ceilings in the showroom create a stack effect which drives the natural ventilation. The temperature stratification created by the stack effect was between 3°C (5.4°F) and 8°C (14.4°F). When the windows and doors were opened, the stack temperatures approached each other suggesting air movement through the showroom. The building occupants were very active in adjusting the doors and windows suggesting that these devices are successful for ventilation control. The effectiveness of the night time ventilation fans is unclear. The limited data on their operation suggests that the clerestory windows and stack effect are the dominant ventilation mechanisms. The simulation of Real Goods Showroom done in CALPAS3 predicted that the showroom would use about 1/6 th of the energy of a conventional commercial building in the state of California. Most of that energy would be used during winter months. The simulation predicted the maximum indoor air - dry bulb temperature on the worst day in December to be around 13°C (55°F) and the minimum outdoor temperature on the same day to be around 8°C (47°F). Some thermal comfort strategies using simulation as a design tool were tested. Our aim by trying these strategies is to suggest ways to improve the thermal comfort of the occupants with minimum use of energy and cost. We didn't find any one strategy which could cost effectively improve the comfort during the winter months. A few relatively inexpensive options are suggested to improve thermal comfort by reducing radiative heat loss from the human body to the exposed cool slab or glass (especially during cloudy days). Covering the slab with rugs and the glass with curtains are an option. Cutting the vines in the winter months to let in more sun may help as our simple sun angle studies showed that solar access was low. Even then some supplemental heating from wood stove might still be needed to maintain comfort. Though daylighting is not addressed in this study, light level measurements were taken on the day of the site visit. This data and observation of the lights at the time of the visit suggest that the daylighting strategies are effective. Overall the passive cooling strategies are effective as the peak interior temperatures remained below 28°C (82°F) despite 33°C+ (91°F+) outdoor temperatures and high occupant densities. The simulations performed suggest that the Real Goods Solar Living Center's Showroom uses a fraction, 1/6, of the energy of a comparable market building. To see a full copy of this report with graphics, checkout the Vital Signs Project Web Site.
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