Frank Fox (left), President of Greenfield Architects, and Jeff Sterner, Senior Vice President/General Manager of High Construction, discuss exterior building options.

Choosing the exterior of your new building wisely is an investment in the life of the structure. However, knowing which type of exterior to select may be a difficult proposition. Jeffrey Sterner, senior vice president and general manager of

Q: Is there a process by which exterior building materials are chosen?

Sterner: Selecting a building's exterior involves many factors. There are subjective issues of image, personal preference, and compatibility with surrounding buildings. There are functional issues of durability and thermal insulation. There may be regulatory requirements from local ordinances, covenants, or building codes. And there are always financial considerations.

Fox: The type of building and the image that needs to be conveyed to the public sometimes dictate the exterior cladding system. A corporate headquarters typically requires a formal, prestigious image, one that can be achieved by using quarried stone, such as granite or limestone coupled with aluminum and glass. An all-aluminum curtainwall system with glass, metal, or thin stone veneer infill panels is ideal for high-rise buildings because such a system is relatively light and performs well in high wind and seismic conditions. Large amounts of glass are desirable in office environments. A school requires a more traditional and durable look, achieved with a masonry product such as brick or concrete masonry units (CMU). A manufactured building, which is strictly utilitarian, may use little or no masonry and rely heavily on a cost-efficient material such as metal siding.

Q: Are certain materials better suited for particular types of buildings?

Sterner: A metal exterior is very economical for industrial buildings but provides limited architectural appeal. Some industrial buildings use masonry walls on the lower half for durability and metal panels above, where they are not so easily damaged. Another option is the use of concrete panels, which are durable and maintenance-free.

Hotel exteriors often are dictated by the standards of the hotel franchise. Exterior Insulating and Finishing Systems (EIFS) are common. They accommodate architectural detailing and different colors but are less expensive than masonry. For a feeling of added quality, masonry is also used in hotel exteriors. Glass is generally limited to "punched" windows that fit in with the modular layouts of rooms.

Fox: Masonry products give schools a traditional and stable appearance with the added benefit of low maintenance. Incorporating traditional roof forms, such as the gable, hip, and shed, covered in a metal roof system to add color and visual interest can further reinforce this image. The use of glass is also important because it is needed to provide sufficient natural light and ventilation within the classrooms.

Office buildings on the other hand can incorporate a wide variety of exterior materials. Architectural interest in office buildings can be achieved by using a combination of materials to express different functions. For example, a glass curtainwall system can be designed to demarcate and celebrate the entrance to the building, and masonry or metal panels may be utilized to articulate the circulation and service elements such as exit stairs, elevators and mechanical spaces. The use of glass is also very important in the design of offices.

Q: How do the materials differ in insulating capabilities?

Sterner: Masonry by itself is not a good insulator, but masonry wall systems can be constructed to hold insulation within cavity spaces. Glass is a key factor in the design of air-conditioning systems, since the solar load on a building frequently dominates the heat-load calculations. Metal is a conductor, not an insulator. Metal wall systems can be insulated, but overall insulating effectiveness is limited by "thermal shorts," the metal-to-metal connections that conduct cold from the outer metal skin through the metal fasteners to the inside structure

Q: How do the different materials last over time?

Sterner: Masonry products are durable and require little maintenance. Glass and aluminum window systems generally do not deteriorate unless the environment is harsh, but they are susceptible to damage. Common maintenance with glass includes recaulking perimeter joints and replacing broken glass. Metal systems need to be repainted if panels chalk, fade or corrode; panels need to be replaced if damaged.