In designing a paint barn, the designer must compromise finish quality in order to achieve the benefits of safety and health, while retaining a low-cost system. The following considerations are important:
- Access to the aircraft
- Multiple uses of a paint facility (such as maintenance) leads to the use of bridge cranes that are difficult to incorporate into an insert
Fall protection around the top surfaces of a paint booth require rugged support structures.
The need for fall protection and an elaborate access structure in a paint barn means there are flat spots on the tops of beams and other items that overspray, dust and even pollen can settle onto. Once these particles are disturbed, they fall onto the object being painted, causing a blemish and reducing quality. Steel beams are a particularly sought-after roost for birds and pigeons. While the inner walls of a paint barn can be sheathed with smooth drywall or sheet metal, the overhead steel and hanging items present another challenge altogether.
Lighting in a paint barn has been uniformly poor in many past designs — in part because lights are typically farther away from the aircraft than they are in an insert, and there is very little, if any, lighting on the side walls. Typically, lights are high-wattage, high-intensity discharge (HID) lamps that drop from the ceiling. In cases where explosion-proof lighting is required, light fixtures become extremely expensive.
Airflow is calculated over the entire cross-sectional area of the barn, even though the process does not use the air at the ceiling level. To reduce airflow to a more reasonable level risks the degradation of laminar flow in the center of the plane (the wings), where a good deal of paint is applied. As the air slows and liquids are added to the air, the density of the air changes and the laminar flow degrades into eddies, producing a cloud of overspray over the head of the painter.
The issues seen in paint barns result in poor finish quality and high instances of rework. In an insert, controlled airflow, a clean environment and high levels of lighting solve these problems.