AAMA CWM-19, Curtain Wall Manual, was published in July 2019 and addresses many aspects of curtainwall design, specification, testing and installation. To explain the document’s history, target audience and to give an overview of how it can be used, the Fenestration & Glazing Industry Alliance (FGIA) hosted a webinar titled, “An Introduction to the Curtain Wall Manual (AAMA CWM-19).”
FGIA technical manager Rich Rinka explained that the document combines information from three documents, which have all since been retired: AAMA CW-DG-1-96, Aluminum Curtain Wall Design Guide Manual, AAMA CWG-1-89, Installation of Aluminum Curtain Walls, and AAMA MCWM-1-89, Metal Curtain Wall Manual.
“They had good information but that information wasn’t complete,” he said, adding that combining the information in one place makes it easier to track, update, sync and prevent conflicting information.
Architects are the primary audience, though Rinka says manufacturers and installers can still benefit from the manual. The document is intended to highlight basic principles and essential requirements of good curtainwall design. It’s more than 100 pages long and is divided into eight sections.
Rinka then explained the manual’s content. He said there are two functions for a wall: to provide structural support for floors and the roof if it’s load bearing and to form a protective enclosure to exclude the elements. The exterior wall also serves as a two-way filter to not only control the flow of heat, light and air, but also moisture, dirt, sound vermin and even people.
While curtainwall, storefront, windows and window walls mean different things to different people, they are often used interchangeably. However, Rinka explained that there are differences.
Storefront are not load-bearing weight systems. They are placed between floor slabs or between the floor slab and the building structure above. These systems are used on lower floors.
Stick built curtainwall systems are shipped to the jobsite in pieces for field fabrication or assembly. They are sealed in the field. Unitized curtainwall is factory assembled and glazed. Most unitized systems are installed sequentially from the bottom of the building to the top.
Window wall systems span from the top of one floor slab to the underside of the floor slab above. Rinka noted that these systems more easily accept operable windows and they can be installed in any sequence.
When designing curtainwall systems, preventing structural failures is the primary concern. Rinka said architects need to consider windloads and other loads on the glass, which often change more drastically and rapidly than they do for the building frame.
“Movement is constantly taking place between components, the wall and the frame, and due to temperature and gravity. This is a key consideration in curtainwall design,” he said.
The manual also explains the importance of weather tightness and energy efficiency in curtainwall design.
Rinka defined tolerances and clearances. Tolerance is a permissible amount of deviation from a specified or nominal characteristic, whether it is a dimension, color, shape, composition or other quality. Clearance is a space or distance purposely provided between adjacent parts, either to allow for movements or for anticipated size variations, to provide working space or for other reasons.
“In all cases, the tolerance specified must be reasonable and realistic,” he said, adding that it’s equally important for the designer to work with the general contractor to establish practical and acceptable clearances. “… The dimension shown on the drawing should be equal to the actual clearance required and account for access to anchors, minimum fire-safe thickness and the outward tolerance permitted for the adjacent construction. It should be determined on the assumption that the construction is as far out of position in the wrong direction as allowed.”
The manual also explains what details are required in drawings and specifications. The complete curtainwall system needs to be shown, including the grid framework, panels, fixed glass, operating windows, doors and other components. Connection details also are important. Rinka explained that the drawings should show connection details between the wall and the building structure, the storefront, roof, floors and ceiling partitions with a precise explanation of where the curtainwall contractor’s work starts and stops.
The Curtain Wall Manual includes 14 mandatory provisions and ten optional provisions. It also gives an overview or lab versus field testing as well as construction schedule and cost considerations.