Creating appropriate indoor conditions for satisfying human thermal, visual, and aural desires has been recognized to be an essential requirement in building design, since the composition of indoor environment parameters have determined human performance and productivity, as well as physical and intellectual capability. However, achieving optimum indoor conditions for building's occupants should also be parallel with energy saving in order to achieve green indoor environment. Thermal comfort is the most substantial among other indoor environmental parameters and has the greatest effect on energy consumption. Shelters in refugee camps in Palestine can experience poor ventilation, lack of natural light and solar radiation, and noise problems, as a sequence of high urban density, absence of green areas, and lack of land; whereas refugee camps in Palestine have one of the highest population densities in the world. Moreover, the cost of energy is high in Palestine and it is the most expensive in all countries in the Middle East. In view of this scenario, this thesis intended to investigate the indoor environment of shelters in Palestinian refugee camps including thermal, visual, and acoustic environment, and other indoor parameters, with focus on thermal comfort, in order to provide suggestions for potential enhancement. The shelters of Special Hardship Cases (SHC) families were selected in this study; whereas the United Nations Relief and Works Agency (UNRWA) for Palestine Refugees in the Near East has been promoting shelter reconstruction programme for SHC families all over the camps. The characteristics of the existing new and old SHC shelters in refugee camps including their design criteria, forms, materials, and surrounding conditions were reviewed to have a better understanding of the nature of these shelters. Studying the two groups of shelters, old and new, was to help assessing the value of the improvement that has already taken place by the UNRWA and to bring greater comprehension of indoor conditions that still need more enhancements. Two main methods, questionnaire and computer model, were employed in this research. Questionnaires were utilized to evaluate the indoor conditions of the SHC shelters including thermal, visual, and acoustic environment, and other indoor parameters, through interviews with a purposive convenience sample of 155 SHC families from Jabalia refugee camp. The gathered data were analyzed by applying various statistical analysis tests utilizing SPSS. Thermal modelling using Thermal Analysis Software (TAS V9.1.4.l) was employed in this study at two stages; to analyse the thermal performance of the existing SHC shelters and to identify the potential enhancement of the proposed alternate materials. Twenty one shelters, old and new, were simulated while three new shelters were selected to apply the proposed fabrics. The survey and the thermal simulation of the shelters revealed that heat loss/gain through shelters' envelopes is one of the most influence factors causing discomfort in majority of shelters. Various shelters' components including; walls, roofs, ground floors and windows; and various combinations of them were simulated to reflect the best thermal comfort levels attained and to reflect the optimum energy reduction achieved. The results could be taken as a guideline for the SHC shelters' envelopes in all refugee camps located in hot humid climates. It is also suggested that similar approaches may be adopted for all refugee shelters located in camps in similar climatic regions. However, the techniques employed in this study may be applicable to other buildings in other locations or climatic conditions. Finally, the thesis drew conclusions and identified areas for further research depending on the findings.