Dampness and Mould - WHO guidelines for indoor air quality - PRWeb

MOISTURE CONTROL AND VENTILATION
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on wind speed and direction. As the forces for air movement depend on the
weather conditions, the openings in the building envelope must be controlled
according to the weather as well as to pollutant and moisture generation. If the
indoor environment is conditioned, the energy used to heat, cool, humidify or
dehumidify the ventilation air can be significant. Therefore, ventilation rates that
are too high should be avoided. High ventilation rates are not a problem in climates
where indoor environments are not conditioned.
In cold and hot climates, the configuration and size of openings are a significant
aspect of ventilation design. As the weather fluctuates constantly, the challenge
of designing natural ventilation is to harness forces determining air movement,
so that the flow into a space is maintained at the desired rate.
Often the term natural ventilation is applied to buildings that are ventilated
haphazardly by relying on the leakage (cracks or porosity of structures) of the
building combined with window openings, which can result in poor comfort and
uncontrolled heat loss. Natural ventilation needs careful design and construction
in order to supply adequate ventilation rates, although the occupant will usually
have to adjust the ventilation openings when necessary. Inadequate ventilation
rates can lead to serious dampness and health problems and moisture damage.
Like any other technical system, natural ventilation has advantages and disadvantages.
Its advantages include:
its suitability for many types of buildings in mild or moderate climates;
the associated open window environment, which is popular, especially in
pleasant locations and mild climates;
high airflow rates for cooling and purging if there are enough openings;
short periods of discomfort during periods of warm weather;
no need to provide space for a ventilation plant;
minimum maintenance;
usually, a lower cost of installation and operation than that of mechanical ventilation;
and
the absence of fan or system noise.
The disadvantages of natural ventilation include its:
lack of suitability for severe climates, where the ingress of very cold air causes
discomfort, condensation and high energy loss;
inadequate control over the ventilation rate, which can lead to poor indoor air
quality and excessive heat loss;
varying airflow rates and patterns of airflow;
impracticality of fresh air delivery and air distribution in large, deep, multiroom
buildings;
inadequacy in cases of high heat gains;