The objective of Subtask 4 in the IEA EBC Annec 68 was to integrate knowledge and results from remaining Subtasks and present them in the context with current knowledge. The focus of the Subtask 4 was on practitioners dealing with ensuring high Indoor Air Quality (IAQ) in modern low-energy residences, the demands and challenges they meet during daily work. This especially includes architects and ventilation designers, facility managers, property developers and employees of public authorities. This publication is a result of Subtask 4’s work. It brings a collection of 24 “case studies” related to IAQ design and control in Low-Energy Residential Buildings. By a “case study” we mean a real life construction project, laboratory investigation or a simulation study that provides innovative approach. The case studies were selected to give the practitioners new insigts, inspiration and motivation to go along new paths leading to sustainable and comfortable homes of the future. The report is organized into three main chapters: “Ways to design residential ventilation in the future” and “Towards better performance and user satisfaction”. The descriptions of case studies are accompanied by “lessons learned” sections aiming directly at practical utilization of results as well as recommended future reading section providing the most important references.