This Guidebook provides a comprehensive overview of residential heat recovery ventilation, regarding design, construction, and operation. In most cases, heat recovery ventilation is the best air exchange solution in moderate and cold climates. The Guidebook is primarily targeted at installers and planners but also contains important information for end users. It combines fundamental principles of engineering with practical hints based on the expertise of Eurovent members. The first two parts are focused on system design and sizing. The third part regards residential ventilation units, which are at the heart of the system. It discusses their essential functions, features, and performance indicators, which should be considered at the design stage. The last chapter addresses system commissioning and operation. This document was published by Eurovent and was prepared in a joint effort by participants of the Product Group ‘Residential Air Handling Units’ (PG-RAHU), which represents a vast majority of all manufacturers of these products active on the EMEA market. This Guidebook was prepared in cooperation with REHVA (Federation of European Heating, Ventilation and Air Conditioning Associations).