Passive House: Building for Comfort and Sustainability
A Passive House is not only one of the world’s leading standards for energy efficiency, but also a building concept designed to create comfortable, affordable, and eco‑friendly homes and buildings.
Where Did the Idea Begin?
The concept was developed by the Passive House Institute in Darmstadt, Germany, in 1996. Passive House is one of the pioneering approaches to low‑energy housing and today remains a global benchmark.
The design focuses on maximizing “passive” influences — such as sunlight, shading, and ventilation — instead of relying on active heating and cooling systems like air conditioning or central heating. Combined with very high levels of insulation and airtightness, this allows a Passive House to use up to 90% less energy than a conventional home.
Passive Houses also offer superior indoor comfort thanks to stable temperatures and excellent air quality. Another benefit is reduced external and internal noise, due to the high insulation levels.
Requirements for a Passive House
To meet the Passive House standard, a building must comply with several criteria:
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Space Heating: Energy demand must not exceed 15 kWh/m² per year or 10 W/m² at peak load (compared to ~100 W/m² in a typical house).
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Primary Energy: Total energy for heating, hot water, and electricity must not exceed 60 kWh/m² per year.
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Airtightness: Buildings must have no more than 0.6 air changes per hour at 50 pascals pressure.
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Thermal Comfort: Indoor temperatures must remain comfortable year‑round, with no more than 10% of annual hours above 25°C.
How Are Passive Houses Built?
To achieve this level of performance, builders use intelligent passive design — ensuring the house is oriented and designed to make the best use of sun and shade, alongside the five principles of Passive House design:
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No thermal bridging
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Superior windows
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Mechanical ventilation with heat recovery
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High‑quality insulation
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Airtight construction
High levels of insulation are key. Heat losses are kept so low that a Passive House can remain warm with little or no heating, sometimes only by pre‑warming the fresh air entering the rooms. The building envelope acts like a continuous thermal blanket, combined with an airtight layer.
Rockwool and Rockzero Solutions
Non‑combustible ROCKWOOL stone wool insulation is ideal for Passive Houses: it fits easily into structures, retains its shape over time, allows vapor diffusion, is durable, fire‑safe, and eco‑friendly compared to many existing materials.
That’s why the Rockzero wall system was created — combining stone wool columns, ROCKWOOL insulation, and airtight OSB4 boards on the inside. Rockzero delivers high energy efficiency, fire protection, and superior indoor comfort.
👉 Learn more at Passive House Bulgaria.
