Ventilation in Passive Housing – Why Doesn’t Airtight Housing Choke?

passive house

We know that ventilation is incredibly important in developing comfortable and practical interior design – but when we’re dealing with a passive house; a highly energy efficient building that is known for its key feature of airtight insulation – the means of ventilation are paramount.

The passive house design means that through high levels of insulation and window energy efficiency, airflow into of out of the building is limited. A complete lack of fresh air amounts to an unliveable building.

Equally important as this highly energy efficient design – which generally gets all the media attention – are the ventilation processes that, as anyone who deals in passive design development knows, are the key element in providing liveable interiors.

However, air quality issues are not the only problem that faces a building that doesn’t ‘breathe’. Moisture can develop, causing mold and other issues.

Passive house designers do however take these issues into consideration and employ strategies to allow for quality interior air, free from unnecessary moisture.

passive house explained

The first step if to include a vapor barrier into the structure, which, as the name would suggest, protects the interior spaces from moisture. The second and most important step is the implementation of mechanical ventilation in the form of a heat recovery ventilator or an energy recovery ventilator.

Passive houses are, after all, guided by stringent energy efficiency standards. Therefore, the ventilation must be energy efficient. These systems, in the most basic terms, exchange the stale air from utility areas such as the kitchen and bathroom and pump clean air into the living room and bedrooms.

While the infiltration of outside air inside may seem like a contradiction to the stringent air tight nature of the building, the HRV or ERV allow interior temperatures to remain stable as heat recovery from the stale air is used to warm the cold outside air as it passes the former, but in such a manner that the two do not become cross-contaminated.

Passive design is an incredibly efficient way to develop residential projects. However, designing in this way brings with it challenges that need to be fully understood in order to create liveable interiors.

 

By Tim Moore
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