This course module is the first one to focus on a core subject of building biology, that is, how to create a comfortable and healthy indoor climate. Only the proper working together of the various indoor climate factors such as air, temperature, humidity, and electroclimate will have the desired effect. This course module is an introduction and also provides an overview of this complex issue. Many of the issues raised here will be discussed in more detail in subsequent course modules such as “Environmental Building Materials Assessment / Building Science,” “Heating and Ventilation,” “Energy-efficient Building Design,” “Electromagnetic Radiation,” “Air and Pollutants,” “Light and Lighting,” or “Natural Colors and Finishes.”