What are the appropriate ventilation systems for a multi-family dwelling?

Since the entry into force of the Technical Code of Building (C.T.E) in 2006, ventilation systems for homes must be mechanical or hybrid, limiting the use of natural ventilation as a complementary ventilation system in kitchens, dining rooms, bedrooms, and living rooms.

Mechanical ventilation is considered mechanical ventilation when the renewal of contaminated air occurs through the operation of electro-mechanical devices arranged for that purpose. In hybrid ventilation, on the other hand, when the environmental pressure and temperature conditions are favorable, the renewal of air occurs through natural ventilation. When they are not favorable, air extraction is done by mechanical means. Therefore, while the mechanical extractor must operate 24 hours a day, the hybrid extractor only operates when favorable conditions for natural draft do not exist.

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The multi-family dwelling: ventilation systems

rnThe grouping of homes in a single multi-family building, also known as collective housing or block housing, represents a significant increase in construction volume, as both the floor area and the height of the building increase. This aspect has many variables especially when it comes to choosing the ventilation system, which must necessarily be a mechanical ventilation for the reasons outlined below.

In mechanical ventilation, the extraction ducts of different housing units can be routed horizontally to a single vertical exhaust duct. However, in a natural or hybrid ventilation system, the extraction from each area in each dwelling must be done through a single vertical duct. The grouping of homes makes this system impractical due to the number of ducts that would be needed to operate the ventilation system. In mechanical ventilation, however, there is no limit to the number of floors that can be served by each vertical duct, which can be used for both air extraction and supply.

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Double flow ventilation systems in the multi-family dwelling

rnDouble flow ventilation systems are characterized by having a heat exchanger that extracts heat from contaminated air and transfers it to the clean air coming from outside. This process is reversed in summer so that the introduced air is at an ambient temperature of approximately 19º C. This way, the costs of conditioning the dwelling are reduced, making it a very efficient system. When employed in a multi-family dwelling, it is usually a centralized system, featuring two collective extractors on the roof. At the same time, it includes a group for supplying clean air from outside to bedrooms and living rooms, and a group for extracting to expel contaminated air from kitchens, toilets, and bathrooms. Each dwelling has its own exchanger, allowing recovery of up to 94% of the heat from the extracted air through the airflow crossing in the heat recovery unit.

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