Why is mechanical ventilation necessary in homes?

The ventilation or air renewal consists of gradually replacing the contaminated air of a room with clean air. Ventilation can be done naturally through the wind or by thermal air movements, or mechanically by means of fans. The need to ventilate homes through mechanical ventilation arises from the high level of insulation and airtightness that buildings currently have. This prevents outside air from filtering spontaneously through façades or door and window joinery, as it used to before.  

Natural Ventilation

In natural ventilation systems, the pressure of the wind on the façades and air movements due to temperature differences are used. This system used in the past is no longer employed in modern homes due to its discomfort and high energy consumption for heating.  

Mechanical Ventilation in Homes: Combined Systems

In mechanical ventilation systems, one or more fans are used to admit air. Sometimes, this admission is done mechanically through a fan via ducts, while the extraction occurs naturally through grills placed in humid areas. Among the advantages of this system are the control of air admission and the possibility of filtering outside air. On the downside, it is a system that does not allow for the implementation of important energy-saving elements and requires periodic cleaning of the air admission ducts. In other systems, the admission of clean air is done through adjustable grills located in the façade, whether by natural or mechanical means. The extraction of contaminated air occurs via an extractor connected with ducts to the humid areas (bathrooms, toilets, and kitchens), from where the contaminated air is extracted to the outside. This system allows for forced extraction, ensuring the flows are guaranteed. The maintenance of the installation is minimal. Conversely, when the wind hits the facade, excessive flow occurs, increasing energy consumption. In winter, discomfort arises due to air currents caused by temperature differences. The acoustic insulation against the exterior is very limited. For nearly a decade, the use of ventilation systems with mechanical admission and extraction has spread, ensuring flows are guaranteed. When a heat recuperator is employed in these systems, the admission of air does not produce drafts and significantly increases the energy savings of the entire installation. It is a system in which, in addition, air can be filtered at the intake points. However, periodic cleaning of the duct system is necessary. It is also essential to calculate and balance the air admission and extraction ducts, as well as the intakes and the heat recovery unit to avoid an annoying noise level. If the heat exchanger does not have an anti-freeze system, if the temperature drops below zero, it may stop or divert the flow through the bypass to prevent ice formation, leading to loss of efficiency.  

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