All quick-acting doors achieve high operating speed by using materials that are light in weight and by using a powerful motor. These are the main types:
• vertical roll-up. This type rolls up vertically on a spindle, like a roller blind. The material for this type of door is a fabric-reinforced plastic or rubber sheet. The door typically includes a plastic window. Figure 1 shows a typical unit in action.
• horizontal roll-up. This type typically consists of two doors, each of which rolls up on a spindle at the side of the door opening. The material is similar to that used in vertically rolling doors. The doors typically have plastic windows. Figure 2 shows a typical unit.
• horizontally folding. This type typically consists of two doors, each of which folds to the side in accordion fashion. The material can be thicker and tougher than that used in rolling doors. The doors typically have plastic windows. Models are
available that include a thin layer of insulation. These are sometimes called “freezer doors,” because they are favored for cold storage applications. Figure 3 shows a unit, with particular features highlighted.
• overhead sectional. This type is a quick-acting version of overhead sectional doors that are used for exterior purposes (which are covered in Measure 6.2.4). The differences are faster operation, greatly reduced infiltration, and tolerance for impacts. Models are available with insulated panels, as shown in Figure 4.