Determining and mapping the base temperature for heating and cooling degree days for Ethiopia

For understanding the heating and cooling degree days, determining suitable base temperature is essential. This study intends to determine and map the base temperatures required for estimating heating and cooling degree days by taking 28 National center for environmental prediction (NCEP) stations that are nearest to the diverse climatic principal cities and towns of Ethiopia. For this, mean daily temperature and relative humidity data were used for the period of 1979–2014, and their values have been analyzed using Olgyay bioclimatic diagram. The representative base temperatures were selected based on temperature percentile indices that fall into the bioclimatic chart. Consequently, the base temperatures over Ethiopia are estimated and mapped using interpolation method in ArcGIS®10 tool. As a result, the minimum base temperature for calculating heating degree days (HDD) with value of 20.2 has been observed in Robe, Combolcha, and Debre Markos, while the maximum base temperature (25.3 °C) for calculating heating degree days (HDD) has been observed in Gode and Hergelle, which belongs to the central and lowland peripheries of Ethiopia. Similarly, the minimum and maximum base temperature for calculating cooling degree days (CDD) with value of 20.8 in Robe and 26.4 °C in Gode and Hergelle has been observed. In total, the base temperature for Ethiopia has been determined to be 21.8 °C for HDD and 23.8 °C for CDD using the mean approach. The study has a potential contribution for engineers, architects, planners, policymakers, and final users to be informed about thermal comfort boundary of the specific climatic zones, aiming to assess buildings and cities energy needs and propose adequate solutions for increased energy efficiency.