ARCHITECTURE, THERMAL DESIGN AND ENERGY

CELINA FILIPPÍN, SILVANA FLORES LARSEN, ALICIA BEASCCHEA

Energy and Buildings: Efficiency, Air Quality and Conservation

Nova Science Publishers, Inc.

Año: 2009; p. 107 - 133

In Argentina the percentage of energy consumption for space heating in buildings is around 30%. In the school buildings in the province of La Pampa (in the central region of Argentina, betweeen 35 and 39º of south latitude) the percentage of heating energy is around 90% (10% = electricity consumption = lighting and appliances). The measured energy consumption is higher than the value estimated according to the Volumetric Heat Loss Coefficients (G-value) and Base Temperature (18ºC), indicating that the students and teachers work with temperatures higher than that value. The cost of the consumed energy corresponds to 17% of the total spent by students. In this context two solar schools (Promoter Entity: Ministry of Culture and Education) were built in different regions, one of great agricultural potential l— cattleman (Catriló); the other, a semi-arid region with low population density (Algarrobo del Águila). Both buildings were designed with passive solar design strategies that exploit the building's orientation, shape, materials, windows, and external landscaping, in combination with passive solar heating systems (direct solar gains through transparent areas and ventilated facade panels) and cooling (natural ventilation and earth-to-air heat exchange through buried pipes), to create a pleasant environment which is less dependent on fossil-fuels-based energy. The schools were evaluated through the results of thermal monitoring and surveys, carried out to analyze the behaviour of the occupants, who explicitly control and affect the internal environment. In the Algarrobo’s school the occupants (mostly with two or three garments inside the classroom — Tshirt, sweater and jacket) were comfortable with temperatures around 17ºC. The heating practically doesn't light during the day and goes out at night. The energy saving in heating is around 90%. In Catriló’s solar school, the average daily temperatures in the classrooms are around 21ºC in winter. Indoors, the students wear only two garments — T-shirt and sweater — or only a pinafore. The heaters work during the entire night and the energy saving is 50%. The results show that the area of comfort doesn't have clearly defined limits; instead, they are defined by those conditions in which a feeling of discomfort doesn't take place. The implementation of passive solar design strategies allowed an energy saving in heating between 50 and 90%, which in turn means a reduction of CO2 emissions. In the case of non-residential buildings, through the technology applied to the envelope design in solar school buildings, the G value was reduced by 35 %, decreasing from 1.40 W/m3ºC (average value for conventional school buildings in La Pampa) to 0.97 and 0.90 W/m3ºC at schools in Catriló and Algarrobo del Águila, respectively. The use of solar technology allowed a noticeable reduction of natural gas consumption in heating, constituting a major contribution in areas of temperate to cold climate, where the greatest energy consumption in buildings values and direct gain values oscillating between 11 and 14 % of the building's useful area, a solar school building may consume at least 50 % less energy in heating to meet occupants' comfort standards. In the case of the school built in Algarrobo, with an average temperature of 17ºC, the consumption was equivalent to the 15% of the average energy consumed by other schools located in different places of the province. The qualitative and quantitative analyses carried out showed promising results related to the buildings’ energy behaviours, yet it cannot be denied that there are certain factors that have direct incidence on the optimal energy behaviour of buildings and their thermal comfort: (a) exogenous factors (the high variability of the external physical environment), (b) endogenous factors (construction characteristics) and (c) socio-environmental factors (life-styles and behaviour of dwellers, associated with the active energy contribution and use of heating ). The true challenge for solar energy architecture is to simplify technology and construction processes so that costs would not be higher than those for conventional buildings, assuring users' proactive behaviour towards the correct building's thermal management. To involve users in these improved practices is yet another challenge.