How the COVID Pandemic and the Energy Crisis Have Influenced Indoor Environmental Conditions in non-residential Buildings

Building energy behaviour and indoor environmental conditions have been changing due to different external events that have been taking place at global level from 2020, from the COVID pandemic (2020-2022) to the energy crisis (mainly from the war in Ukraine from February 2022). During these events, existing naturally ventilated (NV) buildings have had to balance minimum thermal comfort, high levels of ventilation (to reduce CO2 concentration and risk of infection) and the lowest energy costs. Museums and schools are examples of non-residential buildings with different but high specific requirements of thermal comfort and Indoor Air Quality (IAQ). In the case of educational buildings, these requirements are demanding, since the users are children and adolescents who need to concentrate for learning and wellbeing. Schools are occupied during specific class schedules and with high levels of occupancy in the classrooms. On the other hand, demanding requirements are also characteristic of museums, which must ensure adequate indoor environmental conditions for the conservation of collections, all year during all hours of the day, but with low levels of occupancy.
This study presents three case studies, two high schools and a museum, in a location with a temperate climate in the North of Spain. They are NV buildings with low levels of energy performance, working with oil boilers without adequate control and regulation of the heating system. The analysis is based on heating energy consumption and monitoring data from 2019 (previous to the COVID pandemic), during 2020/2021 and 2021-22 (during COVID pandemic) and until 2023 (without any COVID restrictions and during an energy crisis). In addition, the study includes the analysis of questionnaires to the staff (directors and secretaries, and maintenance personnel) and managers (from the public regional administration), regarding their switch of their environmental perceptions and priorities from prior COVID to post COVID and energy crisis. In addition, some answers about their preferences in relation to the energy retrofit priorities for the buildings they have in charge were collected.
School data shows how high level of CO2 concentration prior to the pandemic, are followed by two years of low and adequate levels for a NV buildings during COVID (mean values of 1000ppm). However, after the pandemic, CO2 concentration levels have risen due to the new concerns for energy costs in the two case studies (to mean values of 1500ppm). In all case studies, indoor temperatures have been balanced during COVID to a minimum but with a high energy consumption (up to 30%); and finally in 2022-23, consumption has decreased a 10% since before COVID consequently worsening IAQ. The study of existing NV buildings dealing with external events, helps understanding the potential and benefits of NV. Lessons learned should be considered in the upgrade of existing buildings.