The overall objective of the IEA EBC Annex 68" Project, "Indoor Air Quality Design and Control in Low Energy Residential Buildings", has been to develop the fundamental basis for optimal design and control strategies for good Indoor Air Quality (IAQ) in highly energy efficient residential buildings, and to disseminate this information for use in practoce. The project was defined in 2015, the working phase lasted for the years 2016-19, and the project was concluded with publications on 2020. The project has engaged researchers from 21 companies and institutions from 15 countries.The work has gathered laboratory and field data and developed new knowledge on pollution sources in buildings and how the transport mechanisms for the pollutants interact with heat, air and moisture conditions in materials and indoor zones. Furthermore, the project has assembled a set of contemporary models to simulate the combined heat, air, moisture and pollution conditions of buildings and their assemblies. In addition, a set of so-called "common exercises" about the various subjects have been developed and tested. The purpose has been to identify and describe amenable ways to optimize the provision of ventilation and air-conditioning and to assess possibilities to bring this knowledge into practice.The paper will review the original intentions of the project against the final achievements with the purpose to focus on which elements have been successfully achieved, and to identify areas where the project has only opened research and applications that should be followed up.