Built environment contributes roughly 40% of all greenhouse gas (GHG) emissions produced, and of all primary energy used. The start of the 21st century marks the point when significant improvements were made in building codes from the perspective of energy efficiency and conservation for new buildings. However, roughly 80% of all existing buildings were built before the 21st century. If existing buildings are not taken into account, it is impossible to reach GHG emission and climate targets. The Nordic countries have invested in reducing energy use and improving energy efficiency of buildings since the oil crisis of the 1970s. In these countries building codes are very strict, and energy prices and taxes are very high. These have led the Nordic countries to become pioneers in designing and building energy-efficient, high performance, and low-consumption buildings. Mechanical ventilation with energy recovery units has been the default solution for decades; ground source heat pumps are already very popular and gaining popularity year after year; and nowadays almost all building projects are Building Information Model projects. In this talk I’ll present Nordic insights into HVAC design focusing on energy efficiency, carbon emission, and aspects of public health, including: • How to design more energy efficient and high performance buildings • Steps to reach carbon neutrality • What really matters when designing carbon neutral buildings • Tools to achieve more efficient results throughout the building process • Ventilation’s role in the Covid-19 pandemic The work presented will include results from my two latest research projects, joint with University of Massachusetts Amherst, and Tampere University, Finland.