The ventilation system according to Passivhaus standards

Did you know that the Passivhaus ideal aims to eliminate active heating and cooling systems in homes? Below, we not only explain how a passive ventilation system works but also what the main criteria for its operation are.

The Passivhaus concept, an introduction to comfort ventilation

Passivhaus aims, through the optimization of thermal insulation, improved exterior carpentry, and the elimination of thermal bridges in the building envelope, to minimize the influence of the external environment on the parameters of the indoor environment of buildings. Through strict control of the energy that enters or leaves them, its objective focuses on achieving high thermal comfort.

It seeks the construction of airtight buildings to achieve the highest possible energy efficiency, as unwanted air leaks are minimized. This represents a significant qualitative leap in terms of construction methods. The aim is to control (or manage) the flow of fresh air to ensure the healthiness of the air for the occupants. Healthy air will be free from excess concentrations of indoor humidity and CO₂, where bacteria and fungi have not proliferated, and where there is no presence of bioeffluents and unpleasant odors.

Expand your information on the Passivhaus concept with this video:

The importance of the heat recovery unit in comfort ventilation

If we seek buildings with low energy consumption, the installation of a mechanical ventilation system with a heat recovery unit becomes essential, acting as the “respiratory system of the building.” In these systems, air renewal occurs thanks to the operation of electromechanical equipment designed for this purpose, which can have mechanical or non-mechanical admission. Its advantage lies in its ability to recover a large portion of the energy from the air expelled outside the building at the moment renewal occurs (the stale air expelled is replaced with clean, fresh air pushed inside).

Description of the components of the dual flow method with heat recovery

How does a dual flow ventilation system work? In these systems, the central unit (which requires very little space, allowing it to be installed in a storage room or even a closet) includes the following: a heat exchanger, fans, filters, air conditioner, air preheater, and humidity extractor or air dehumidifier. Thanks to the heat exchanger, the contaminated air from the humid rooms of the house (kitchens, bathrooms, and toilets) transfers its thermal energy to the incoming fresh air before being expelled outside. Thus, it ensures that the temperature of this incoming air approaches the indoor temperature of the house. Thanks to this system, recovery rates of up to 90% can currently be achieved.

Characteristics of the ventilation system

When installing a dual flow ventilation system in our home, we must ensure that it has the following characteristics:

• For hygiene reasons, a maximum air exchange rate (efficiency) of 0.4/hour is required. With this air exchange rate, a maximum of 1.5 kW of energy can be supplied to a residential building of 140 m₂.
• The section of the main ducts must be larger than 20 × 20 cm; that of the branch ducts must be larger than 15 × 15 cm.
• The central unit must have acoustic insulation.
• The mandatory maintenance of the installation (filter change and cleaning of the unit) should be easily executable.
• The system should easily adapt to the needs of each user, allowing the incoming air fan to be disconnected when windows are opened during the summer. In addition, the supply outlets will allow for flow regulation in dry rooms, while the extraction outlets will allow for flow regulation in humid spaces.
• Fresh air intake will be made through a terminal located in the exterior wall, or through the geothermal air collector.
• The central unit must guarantee the recovery of more than 90% of the energy from the expelled air, allowing for the preheating of the air supplied to the house.
• The air distribution networks will allow for optimal ventilation to adapt to the needs of each room.
• It will have insulated ducts that reduce thermal losses and prevent condensation in the ducts. In the case of load losses, these should be minimal.
• They will be lightweight, sturdy, and weather-resistant.
• Stale air will be expelled through a terminal located on the roof of the building.