In the light of increasing the world energy demand, several conventions are developed to reduce energy demands in the building sector (exiting and new) including the historical ones such as 2030 energy strategy in the EU. The historical buildings attained international concern, since they have significant value that requires to be protected. Also, dealing with energy saving in historical buildings requires certain regulations, theoretical, and practical researches for conserving their cultural significance and heritage value.
Thus, this was the reason behind issuing the first law in EU so called “Conservation of cultural heritage – Guidelines for improving the energy performance of historic buildings- FprEN16883” at the beginning of 2017. In addition, several projects such as 3ENCULT & EFFESUS were conducted for addressing this matter. Also, the results of studies have been carried out in Sweden to balance between the energy conservation and building conservation have shown that 20% of energy saving can be achieved without damaging the cultural heritage value \citep{_ahin_2015}. However, the same question remains, “is it possible to achieve balance between thermal comfort requirements and conservation issues in other climate zones such as hot arid zones?”.
In the other countries such as Egypt, the links between the cultural heritage, thermal comfort and energy saving requirements are still missing. Although, the historic buildings in old Cairo area constitute a large portion of the built environment as per URHC maps and the above-mentioned charts. These buildings are very valuable in terms of heritage and they also deal with environmental issues. Ottoman houses give example on that kind of valuable buildings. So, preserving these houses must respect the original culture significance and the recent conservation issues.
Balancing between conservation and thermal comfort requirements has to be applied to maintain the cultural heritage and to develop the technologies to meet the historical building’s needs. So, the debate about this topic shall be performed through theoretical, analytical, and practical studies in different climate zones such as hot climate zones.

RESEARCH QUESTION

Is it possible to achieve balance between the thermal comfort  requirements and conservation requirements in the naturally ventilated  historical  buildings in hot arid zones?

CONCEPTUAL  FRAMEWORK

Thermal comfort requirements and building  performance issues in the historic buildings require multidisciplinary approach  concerned with buildings that were designed in a specific period for a certain function to meet the need of their  inhabitants and protect them from the climate  conditions at that time. As time passed on, these buildings became an  essential source of information about the history but in order to maintain  these buildings the need of the current community and current climate conditions  should be evaluated. Analysing the variables in this topic should be carried  out in order to evaluate if it is useful to restore the natural ventilation  system nowadays or it is better also to consider additional solutions to  preserve architectural heritage and building use. Figure (5) shows simply the main variables in balancing between cultural heritage and thermal comfort requirements. The conservation issues and building energy performance issues will be discussed in this part.