More intermittent energy production and increasing electricity demand poses new challenges for the power grid. Demand response, DR, in buildings has the potential to be part of the solution. This study investigates the potential of using the ventilation system in a timber-framed office building to contribute to DR by reducing airflow during selected periods. Using building energy simulations, several ventilation reduction scenarios from 15 minutes to four hours with different airflows were analysed under a year and in varying weather conditions. The results show that thermal comfort, not air quality, is the main limiting factor when reducing airflow in this office building. Even short reductions of 15 minutes can lead to uncomfortable temperature increases, especially in sun-exposed or densely occupied areas. While some flexibility exists—particularly during winter mornings—the overall potential is limited. With a seasonally adapted ventilation reduction strategy, up to one hour ventilation reductions are possible most of the days over the year and still maintain acceptable indoor climate due to the Swedish work environment agency and the European standards. The cost savings were rarely achieved due to compensatory energy and air flows needs. External conditions such as solar radiation, outside temperature and building orientation significantly affect performance. The power saving potential differ between 0-20 kW for the scenarios that still managed to keep the indoor climate within the European standards. The study concludes that ventilation-based demand response may only provide modest benefits and is most useful when integrated with other systems and coordinated across many buildings.