indoor air quality

Stack ventilation systems were installed in German schools constructed around 1900 and are no longer in operation. The aim of this study was to show how reactivating these systems could improve the indoor air quality in classrooms. Ventilation stacks were reactivated in three classrooms in a school while a fourth classroom, which was naturally ventilated via openable windows, served as the reference case. All classrooms were measured for carbon dioxide levels, air temperature and relative humidity.

Occupants spend a significant amount of time indoors where temperature and air quality has an important impact on their comfort, health and work performance. Understanding the role of airflow exchange between spaces is crucial to describe the processes of mixing and transport of substances driven by air motion and therefore essential for evaluating indoor air quality. This work presents the results of field measurements and laboratory experiments designed to characterise door operation and to quantify its influence on air volumes exchanged between rooms due to door motion.

Most HVAC systems are designed to supply air based on assumed (usually maximal) rather than actual occupancy, therefore often resulting in over-ventilation. The concept and theories of demand-controlled ventilation (DCV), which are to find better ventilation strategies according to actual occupancy, have been developed for more than two decades and have been applied to many situations. However, a certain type of room (i.e. short-term occupied room) seems to have been neglected in the literature of DCV.

For over a decade now, the OQAI — Observatoire de la qualité de l’air intérieur [French observatory for indoor air quality] — has been leading research into indoor air quality and occupant comfort in living spaces: housing, schools, offices, leisure spaces.

Adequate ventilation is necessary to maintain thermal comfort and remove indoor air pollutant concentrations (Crump et al., 2005). Indoor pollutant concentrations vary considerably depending on occupants’ behaviour patterns, building characteristics and meteorological parameters and seasonal effects. Experimental measurements are time consuming and expensive to carry out, while computational models are regarded as a valid complement.

Numerous studies have investigated the application of multi-zone demand-controlled ventilation for office buildings. However, although Swedish regulations allow ventilation rates in residential buildings to be decreased by 70 % during non-occupancy, this system is not very common in the sector. The main focus of the present study was to experimentally investigate the indoor air quality and energy consumption when using multi-zone demand-controlled ventilation in a residential building. The building studied was located in Borlänge, Sweden.

Traditional building technologies establishing highly-breathing multi-layered wall systems provide healthy indoor environment and energy efficiency in buildings due to the use of lightweight, porous, water vapour permeable and thermal resistive building materials. The breathing performance of traditional buildings and materials that contribute to the healthy indoor conditions and air quality are needed to be investigated in detail.

Demand controlled heat recovery ventilation systems, which combines heat recovery (HRV) and demand controlled (DCV) is growing fast among ventilation manufacturers.

Several categories can be identified, from global dwelling regulation, to fine room-by-room regulation of the airflow rate. Simulations show that room-by-room demand controlled heat recovery ventilation is the best compromise to optimize at the same time indoor air quality, comfort, and energy savings.

Increasing airtightness and isolation of residential buildings in today’s climates cause challenging situations for the summer indoor climate. In combination with ventilation for fresh air, it calls for intelligent control of passive cooling when available, and active cooling when needed.

The combination of heat recovery ventilation and an air-to-air heat pump cooling system is a solution to these challenging situations. With the exhaust air heat pump cooling system, heat is transferred from the supply air (which is getting colder) to the exhaust air (which is getting warmer).

Is Demand-controlled ventilation a relevant answer to face the new challenges of the Building sector, which requires everyday higher energy efficiency and better indoor air quality? Can Demand-controlled ventilation be considered as an alternative to heat recovery ventilation, through an affordable and low maintenance solution? Since the take off of the DCV in the early 80’s, these questions have been considered many times.