S. Hossein Sagheby
Associate Professor, Hochschule für Technik und Wirtschaft (HTW) Berlin – Dep. of Building Energy and Information Technology, Berlin, Germany

A set of communicating sensors with a microcomputer is designed to enable an interaction between the room and the occupant through a dynamic feedback system and easy-to-understand signals. This approach represents a method of using the new advances in microcontroller technology to promote indoor air quality especially in residential buildings.

Keywords: Eco-Feedback, Information and communication technology, CO2-meter, Human-Room Interaction


People in industrialized societies spend most of their lives indoors. In the past decades, energy saving measures have led to the construction of airtight buildings. This can negatively impact the indoor air quality by allowing a build-up of air contaminants within a building section if sufficient ventilation is not provided. In residential buildings in Germany the dominant mode of ventilation is natural ventilation through hand operated windows. Healthy indoor air depends on the rate of delivering fresh air to the environment and also on the indoor production rate of the contaminants. Especially in heating season an excessive ventilation time or an incorrect ventilation type can result in higher heating energy consumptions, whereas a less-than-necessary ventilation time leads to an accumulation of contaminants in a room and therefore causes dissatisfaction of the occupants.

Poor indoor air quality (IAQ) in residential buildings can also have direct economic drawbacks. An increasing number of employees working from their homes signify the economic importance of the IAQ in residential buildings. Better IAQ results in more productive and happier occupants. While it is difficult to exactly quantify these benefits, there is continuing evidence of higher productivity in areas with better IAQ.

The sensitivity towards the actions controlling air quality is very diverse. About 59% of Europeans seem to lack information about the air quality issues in their country [1]. The survey was conducted mainly to assess the topic of general air quality, but it gives an impression of the number of people who may also be uninformed about the topic of IAQ in their homes.

Many studies have shown the effectiveness of feedback systems in persuading occupants to have a more IAQ-aware and energy-efficient ventilation in their buildings (see e.g. [2] and [3]). The advantages of feedback systems are twofold. They represent a low-cost method to promote efficient behaviour and therefore decrease energy consumption, and behavioural persuasions are less likely to produce the undesired rebound effect.

In most cases feedback is carried out through information campaigns and printed media, which address the general consumer and aim at listing and describing all relevant cases of efficient behaviour. With the advent of modern low-cost sensors and communication, as well as data processing technology, there is an opportunity for a dynamic and active feedback system. The purpose of this study is to provide the proof of concept for a personal feedback system using low-cost sensors with a controller unit to increase awareness of the state of the IAQ and to promote better indoor air quality, and efficient ventilation behaviour in naturally ventilated rooms among occupants in residential buildings.

System description

The ambient status is gathered by a set of sensors that relay data to a single-board computer (Raspberry Pi with a USB power source) where the processing and storing of the data are carried out using an open source robust data collection and automation software. The data is stored locally on a memory disk and on an external hard drive for further analysis. The concept of this system does not introduce actuators like in classical smart home systems therefore eliminating the related investment, maintenance and operational costs. The system acts as a suggestion platform and actively provides feedback to the occupants. Figure 1 shows the schematic of the design principle.