Muro (Koji room)
Japanese: 麹室（こうじむろ）
A dedicated room with controlled temperature and humidity for growing koji.
The koji room is a space dedicated to koji making, maintaining constant temperature and humidity. Traditional muro has well-insulated walls and ceiling, kept at 28-38°C and 60-90% humidity.
Koji trays are arranged on shelves inside, with regular temperature monitoring. At home, a styrofoam box or cooler with hot water bottle substitutes. Scale differs, but the principle is identical — providing a comfortable environment for koji growth. Even a simple home koji room produces excellent koji if temperature and humidity remain stable. What matters is not equipment size but the mindset of maintaining the right environment.