This article presents the results of a Dutch national study into performance of mechanical ventilation systems and its effect on the self-reported health and perceived indoor environmental quality of occupants. Ventilation systems with natural supply and mechanical exhaust ventilation (MEV) and balanced mechanical supply and exhaust systems with heat recovery (MVHR) were investigated. Surveys were performed in 299 homes, which included visual inspections and measurements of ventilation rates per room and installation noise levels. An additional survey regarding perceived indoor air quality and self-reported health was completed per household. Results show that shortcomings are common in many homes and for both MVHR and MEV. Shortcomings include insufficient ventilation rates, high noise levels, unclean systems and insufficient maintenance. The causes have been found to be related to failures during all the different stages of the building process, from design to use. The indoor environmental quality was perceived more positive in homes with MEV when considering air quality, perceived dryness of air, noise and control options. There was no clear relationship between self-reported health and shortcomings of ventilation systems. Some practical implications are presented to avoid shortcomings in future dwellings.

An Indoor Environmental Quality (IEQ) label (or 'IEQ profile' as it is called in the Netherlands) has been developed in the Netherlands specifically for homes. The label is meant to be used in conjunction with the standard energy label and the graphic design is set up accordingly. The IEQ label expresses the 'risk level' for eight distinct IEQ aspects: thermal comfort in winter, overheating in summer, air exchange (ventilation), moisture & mould, combustion gasses (from heating appliances), daylight penetration, noise from installations and noise insulation. The method for the IEQ label has been recently published in the Netherlands and a pilot project has been carried out in which the first 11 homes in the Netherlands have been provided with this new IEQ label. Most people do not consider IEQ when e.g. buying or renovating a house. The IEQ label visualizes information about comfort and health quality of a home to (future) inhabitants. It thereby assists them in making informed decisions about comfort and health related issues when improving the energy performance.

The quality of mechanical ventilation systems (mechanical air supply and exhaust and natural air supply and mechanical exhaust) was studied in 299 recently built single-family houses. The quality of ventilation systems was determined by measurements as well as technical inspections for the aspects indoor air quality, thermal comfort and noise. The performance was generally poor for both types of ventilation systems. Common shortcomings regarding indoor air quality are insufficient air supply and exhaust rates, improper construction of ductwork, insufficient control options and poor maintenance. Common failings regarding thermal comfort are overheating if no 'bypass' section is installed as well as draught under air supply valves. Common shortcomings regarding noise are the position of the ventilation unit, the absence of properly installed silencers, and improper construction of ductwork. The overall poor performance seemed to originate from flaws in design, construction, maintenance as well as the use of the ventilation systems.