Combating climate change requires a significant reduction of energy use, in particular that used for heating and cooling of buildings. Innovative solutions, such as the hybridization of ground-source heat pump (GSHP)-based heating, ventilation and air conditioning (HVAC) systems with personal comfort systems (PCS) and natural ventilation (NV) can be employed to improve energy efficiency. However, although climate change will alter the need for HVAC and the efficacy of passive solutions, most building energy simulations use historical weather data, and thus, do not consider the effects of climate change. This study focused on the impact of warmer future weather on the performance of eight heating and cooling scenarios, which result from different combinations of heat pump, either air-source (ASHP) or ground-source (GSHP), and PCS and/or NV, in an office building in fourteen cities across the Iberian Peninsula. Building energy simulations confirm that, while heating loads decrease in most cities, cooling thermal demand increases significantly as a consequence of warming due to climate change. The resulting increased energy imbalance increased heat build-up in the ground, reducing the thermal load satisfied by the GSHP. The warmer outdoor air and ground led to lower cooling coefficients of performance (COP) for the ASHP and GSHP, respectively, which, with the increased need for cooling, resulted in electricity needs for heating and cooling increasing significantly. Revised simulations based on decreasing the internal heat load generated by equipment and lighting were carried out to explore measures that could be used to mitigate these climate change impacts. The reduction in internal loads resulted in a noticeable shift in the thermal loads towards the heating demand. This reduced imbalance resulted in a decrease in cooling demand, as well as a lower build-up of heat in the ground, which consequently improved the coverage of the load by the GSHP and increased the cooling COP, resulting in a decrease in electricity needs for heating and cooling of up to 71%, relative to standard internal loads. Display omitted •Climate change will alter heating and cooling needs and passive solutions' efficacy.•Building energy simulations were performed with late 21st Century weather in Iberia.•Climate change reduced overall heating and cooling efficiency.•Lower internal equipment and lighting heat load decreased load imbalance.•Hybrid solution and lower indoor loads decreased electricity needs by up to 71%.