Comfort ventilation, which includes supply and exhaust systems with heat recovery, is becoming increasingly popular in older buildings - and for good reason: in addition to providing high indoor air quality and comfort, they ensure lasting protection against structural damage. This book aims to facilitate the retrofitting of heat recovery systems in existing buildings and to present new solutions and simplifications. The latest research findings and ventilation concepts contribute to this, as do innovative products that have been specifically developed for renovations in recent years. These are also presented in an easily understandable and practical manner in this book.