Energy efficiency and comfort aren't synonyms. In modular construction, they can be in tension.

High-efficiency modular architecture brilliantly solves the building envelope.

But a sealed module that performs well energetically is also a high-risk environment for indoor air quality.

Energy efficiency and comfort aren't synonyms. Sometimes they're in tension.

The Passivhaus paradox

A Passivhaus building is built to minimize heat loss. The envelope is practically airtight. This is exactly its energy strength — and its vulnerability for indoor comfort.

In a high-airtightness envelope, natural air exchange doesn't happen. The air we breathe — with CO₂, humidity, volatile organic compounds — stays in the space until the mechanical ventilation system replaces it.

The critical parameter: Mean Age of Fluid

If the ventilation system is correctly sized but air distribution isn't verified with CFD simulation, there are zones where exchange doesn't happen within the expected time. The Mean Age of Fluid can range from under 100 seconds near the vents to over 600 seconds in the module's most remote corners.

Fluid dynamics simulation resolves that tension before production — when every change still has an affordable cost.

Before finalizing the layout, it's worth asking: where in this module will the air be worst in six months? Whoever asks it first builds spaces that never disappoint.