Thermal analysis of low-cost dwellings in Mexico using greenroofs

According to the National Energy Balance (1), the electricity consumption in the residential and commercial sector represents thirty-three percent of the total consumed in the country. Most of the energy is consumed during the summer, when it is necessary to use air conditioning to maintain comfort conditions inside buildings. This aspect takes relevance in warm-dry climates, where a deficient design of building envelope and a wrong location of windows can increase the thermal loads producing an extra load to air conditioning systems and high costs by electricity energy consumption. For this reason, adequate design strategies and thermodynamic concepts have to be applied in order to make dwellings comfortable. Two dwellings are simulated and analyzed, the first one is made of regional materials like traditional concrete block walls, reinforced concrete roofs and economic finishes, the second one is proposed with a green roof and insulation in walls. The heat gains through the different constructive elements have been obtained, to analyze their impact on global thermal comfort and the electricity energy consumption of air cooling systems. Also, an exergy analysis has been applied to analyze exergy efficiency of air cooling systems and the influence that the building envelope can have in them with the proposed changes. The minimum exergy expenditure of air conditioning systems required to achieve comfort conditions inside dwellings could be a useful benchmark for the comparison of various dwelling designs. Copyright © 2011 by ASME.