‘Ventilation’ is a theme in the chapter ‘Installations and appliances’ (see the recommendations). Noxious substances – among which particulate matter and germs – need to be kept out or expelled; ventilation is about the removal of these substances and the supply of fresh, clean air. Ventilation primarily addresses the circulation of indoor air purity and humidity. Furthermore, proper ventilation dispels odors, regulates temperature and abates noise. About the latter: noise produced by ventilation systems is often a big problem but a well-designed model can abate noise from entering through natural ventilation openings such as windows.
Natural or mechanical?
Two Dutch engineering students discuss the choice between natural versus mechanical ventilation in the context of (special) education where air quality is a major problem. Advantages of natural ventilation are that users have more control and that noise from the machine and airflow can be avoided. Outdoor conditions – wind, weather and temperature – create disadvantages for the reliance on natural ventilation systems though flow barriers such as screens and grates which automatically close when the wind increases may help lessen these negative impacts.
Location can create other serious obstacles to proper ventilation: for example, consider the intake of polluted air and (traffic) noise. It may be possible to manage the averse conditions by combining natural and mechanical ventilation so that the intake is mechanical and the expulsion natural; the clean and/or silent side of the building should be chosen for the intake.
From every day experience it appears open bedroom windows are counterproductive because they are often closed for fear of burglars, insects, wind or noise. Sizeable ventilation screens – along with security grates and, if necessary, a sound buffer – are recommended in these cases.
The remedy may be worse than the disease
Elsewhere it was remarked that sensory demands on homes and buildings can be contradictory. Generally this is true for the noise of ventilation systems (in schools, see here) which should be weighed against odor- or temperature oversensitivities.
‘Worse than the disease’ may concern people for instance to whom even a ‘silent’ ventilator in the bathroom is more unbearable than the toilet odor it is meant to suppress.
In a different way something similar has to do with the fact that most ventilation systems are very maintenance sensitive which carries the danger that they contribute to the problem they’re meant to solve: polluted air. The above mentioned students claim that the design requirements for ventilation systems are insufficient and that they are too sensitive to mistakes in installation and calibration. Inadequate maintenance can create a favorable climate for noxious micro organisms at places which collect moisture. They also claim: ‘At smaller installations and in the absence of humidification mold growth can occur in the ducts.’
In its report on indoor air quality in primary schools, the Dutch Health Council emphasizes that these systems should be very well maintained because negligence in this respect will import even more noxious compounds into the schools.