Analysis of the hygrothermal conditions of the Vinalopó Medio cave houses (Alicante, Spain)

• For the first time, the interior comfort of the Alicante caves has been verified. • The energy efficiency of cave is better than that of a similar conventional house. • Excellent comfort and energy efficiency are achieved by simply including heating. • These excavated homes are among the most sustainable living spaces possible. Traditional excavated houses possess significant potential for adaptation to contemporary lifestyles while addressing sustainability challenges in construction. In the Vinalopó Medio region of Alicante, Spain, there exists a considerable number of historic cave dwellings that remain inhabited, yet there is a dearth of studies on these structures. It has become essential to investigate the indoor environmental conditions to identify necessary improvements in three selected case studies. The analysis of indoor and outdoor temperature and relative humidity was conducted at various times throughout the year. To draw robust conclusions, a comparative analysis with similar previous studies is presented, utilising Givoni’s psychometric diagram. The findings indicate that the interior conditions of the caves are generally close to acceptable comfort levels, with an average temperature of 20.4 °C and relative humidity of 54.7 %. This suggests that only minimal internal heating is required during the winter months. Furthermore, natural lighting levels were measured in one of the case studies, revealing very low values that necessitate the consideration of systems to enhance the entry of natural light into the interiors. Energy efficiency was assessed by evaluating the heating and cooling energy demands alongside an overall estimation of non-renewable primary energy consumption and carbon dioxide (CO 2 ) emissions. The results were compared with those of a conventional house built during a similar period in the same area, demonstrating that the energy demand for cooling in the cave houses was reduced by 77.50 % compared to the conventional dwelling. To enhance energy efficiency, indoor comfort and natural light levels, it is proposed that systems be installed that respect the heritage of this excavated architecture. Such interventions would enable the achievement of optimal energy performance, resulting in CO 2 emissions of 5.60 kgCO 2 /m 2 per year and non-renewable primary energy consumption of 32.80 kWh/m 2 per year.