Passive Houses and Direct Solar Gains: A Practical Strategy for Reducing Energy Consumption

The European Green Deal aims to achieve a climate-neutral economy by 2050 through a transition from fossil fuels to renewable energy sources (RES). Despite strong political support, the transition faces major limitations due to growing global energy demand, and strong dependence on imported energy and materials. Fossil fuel use and CO2 emissions continue to rise globally. In Slovenia, the share of RES in primary energy has increased to about 20%, mainly due to biomass and hydropower, while solar photovoltaic (PV) systems – despite significant subsidies – contribute only a small share of final energy. This paper argues that reducing energy demand is more effective than attempting to meet ever-increasing consumption with renewable supply alone. Special emphasis is placed on energy efficiency in buildings, where heating and cooling represent the largest energy demand. A detailed case study of a passive wooden house in Ljubljana is presented, analysing electricity consumption in 2023 and 2024. Results show extremely low heating energy demand (below 15 kWh/m² per year), strong dependence on winter conditions, and no need for active cooling even during summer heat waves. The study demonstrates that passive solar design, high-quality thermal envelopes, and efficient technical systems provide a robust, comfortable, and economically viable pathway toward low-energy and climate-resilient buildings.