The selection of the researches, to be  analysed in this state of art, based on the following factors, Ref. to Table D in figure (16):
- Researches that have applied or  proposed criteria to improve thermal comfort or energy efficiency or both of  them in the historic residential buildings (houses) in Mediterranean and hot  arid zones.     
- Researches that have used the  environmental concept that is embedded in the historic residential building to  improve the contemporary architecture.
- Researches that have dealt with  the above-mentioned issues but they have specially studied Ottoman houses in  different regions.    
The reason behind analysing researches and  case studies that are located in hot arid and Mediterranean zones, is  distribution of Ottoman houses. Hence, Ottoman empire were located mainly in  Turkey, North Africa (Egypt, Algeria, etc.), and Balkan countries.