D. Comparison  and discussion
This step will include discussion about the  following items with suggestion for improving: 
- Egyptian laws in preservation  and conservation
-  Egyptian code of energy  efficiency of residential buildings
- Suggestions for several  retrofit actions in the historic residential buildings “Ottoman period” in Cairo.

EXPECTED  RESULT

Research aims to achieve the following items:
- KNOWLEDGE about the Ottoman houses in Cairo and other regions. This knowledge  includes construction system, material, etc.
- ANALYSING the concepts, methodologies and tools used in similar built  heritage or European conservation projects and how they succeed in achieving  the balance between thermal comfort requirements and conservation principles.
- ADAPTING the achieved methodology for optimizing appropriate tools to  evaluate the thermal comfort inside houses in hot arid zones.    
- APPLYING these methodologies in case studies of houses in Ottoman period in  Cairo after matching the concepts alongside with each case.
- DISCUSSING  & EVALUATING the appropriate new function (re-use) for these  houses.
- CONCLUDING the method that is used in the PhD.
- CREATING  GUIDELINES for conserving the historic houses in hot arid zones.
- EXPANDING  the guidelines to other Ottoman houses in other regions          
Finally, those concepts shall respect the thermal  comfort factors during the restoration work. In addition, the discussion of the  balance between conservation issues and buildings performance issues under the  current conservation laws in Egypt must be considered.

RESEARCH  IMPORTANCE

This research introduces the importance of  applying thermal comfort concepts as a indispensable priority in the  conservation of historic residential buildings especially in the hot arid  zones. These buildings were designed to be naturally ventilated, so thermal  comfort factor shall be considered as an essential requirement.
a) It suggests suitable  methodologies and tools to apply this factor in the natural ventilated  historical buildings before and after doing the restoration work to avoid  damaging or malfunctioning of the historical buildings.
b) It discusses the reuse strategy  in Ottoman buildings to find appropriate best practices and to extend that  strategy for other historical residential buildings.
c) It reveals the differences  between the Egyptian conservation laws with respect to the European laws.
d) It supposes to reduce the energy  demand in existing historical houses in Cairo.

RESEARCH  PROGRESS and CURRENT STATE