indoor air quality

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.

The indoor climate in residential buildings is affected by the people that live in the house and their activities. One of the goals of a ventilation system is to prevent excess humidity in the house by removing part of the moisture. The moisture balance can however be distorted in winter with a low humidity in the house as a result.

The aim of improving air tightness of structures is to prevent the uncontrolled air leakages through structures. Built environments contain microbes, particulate and gaseous impurities but removing them is not always necessary. For example, an ageing building envelope commonly contains microbial impurities even when there is no obvious moisture damage. Air leaks convey impurities to indoors where they can lead to poor indoor air quality and associated health problems. Air leaks have also negative impact to energy efficiency and living comfort.

Many studies about photocatalytic oxidation (PCO) have been carried out in laboratories. They use an inert test chamber with ideal indoor conditions: a low volume, a controlled temperature and humidity, and a constant injection of one to five specific gases. The principal aim of this study was to implement, in a real test room (TR) of an experimental house, a titanium dioxide (TiO2) layer to quantify its efficiency.