Which type of factory-built fireplace does NOT have grills or louvers on the face?

The correct answer is that a radiant factory-built fireplace does not have grills or louvers on the face. Radiant fireplaces are designed to focus on the radiation of heat directly into the living space, providing a warm and cozy ambiance without the need for additional air circulation features typically seen in other types like circulating fireplaces. The absence of grills or louvers allows for a more streamlined aesthetic and enables the radiant heat to transfer more effectively to the surrounding area.

In contrast, circulating fireplaces utilize grills or louvers to help distribute heat more widely throughout a room or home. High-efficiency units may also incorporate such features as part of their design to maximize heat output and efficiency. Conventional fireplaces generally have designs that include external elements like louvers for better airflow management, contrasting with the more minimalistic approach of radiant models.