Exterior Building Enclosures

Design Process and Composition for Innovative Facades

Keith Boswell

• Publisher: Wiley
• Year: 2013
• ISBN:
  9781118330067
• Edition: 1
• Topic: Architecture
• Subtopic: Conception architecturale

A comprehensive guide to the design and execution of sophisticated exterior building enclosures

Focused on the design process for architects and related professionals, this book addresses the design and execution of sophisticated exterior building enclosures for a number of commercial building types and in a variety of building materials. It focuses on the design process by delineating enclosure basics, the participants (owners, architects, engineers, consultants) and their roles and responsibilities through collaboration, and tracking the design process through construction.

This comprehensive handbook covers all of the factors that affect the design of a building enclosure, including function, visual aesthetics, performance requirements, and many other criteria. In-depth case studies of projects of various scales, types, and climate conditions illustrate the successful implementation of exterior wall enclosure solutions in brick masonry, stone, architectural concrete, glass, and metals.

This unique and indispensable guide:

• Defines the functions, physical requirements, design principles, and types of exterior building enclosures
• Identifies the participants in the design and construction process and specifies their roles and responsibilities
• Presents a step-by-step process for the design of exterior enclosures, from defining goals and developing concepts through creating construction documents
• Reviews the construction process from bidding and negotiation through the paper phase to the "brick and mortar" stage
• Provides details on the properties of exterior enclosure materials, including structural considerations, weather protection, fire safety, and more
• Covers a variety of materials, including brick masonry, natural stone masonry, architectural concrete, metal framing and glass, and all-glass enclosures

Written by the technical director of the San Francisco office of Skidmore, Owings & Merrill, Exterior Building Enclosures is an indispensable resource for architects, engineers, facade consultants, and green design consultants working on commercial building projects.

Chapter 1

Basics

You have to learn the rules of the game. And then you have to play better than anyone else.

ALBERT EINSTEIN

Good building design and good exterior building enclosure design don’t just happen. “Good” is a broad, subjective, and sometimes overused term, used primarily to describe the visual aspects of design. It is open to many interpretations. In exterior building enclosure design, visual appearance is generally considered the major component of good design. It has been said before that beauty is in the eye of the beholder. Exterior appearance is very important; however, exterior building enclosure design is more than just visual appearance. It is the integration of the science of physics with the science of materials. It is the integration of materials, material properties, and performance design principles. It requires a basic understanding of building and construction sequencing. It is the application of science and design principles with the art of composition. It is in this intersection of science, art, materials, construction, and many other factors where design and technology, art, and science become architecture. In complete design of exterior building enclosures, beauty is more than skin deep.

Understanding the Basics

Every building design and the associated exterior enclosure design are unique for the particular project. This is the case no matter the size or location of the project. Large or small or any size in between, exterior building enclosures are planned, researched, designed, detailed, and executed to look good and achieve defined performance levels per criteria established for the specific project. Before beginning exterior enclosure design for a project, it is imperative that the architect possess or acquire a basic understanding of the intended and necessary functions of the enclosure, the elements and forces acting on and influencing the enclosure design, performance design principles and associated physics, and the basic types of exterior building enclosures. In conjunction with these items noted, project delivery methods will determine the extent of detailed design to be performed by the architect and design team or by delegated detailed design to participants of the construction team. This embedded or acquired knowledge and identification of design responsibility, coupled with the design intent, is required to provide complete enclosure design.

Some exterior building enclosures are fairly simple. However, with higher performance expectations, emerging technologies, and regulatory standards, proposed designs may require a higher level of detail, documentation, and construction technology to execute. As the old English proverb states: “You have to crawl before you can walk, and walk before you can run.” So, getting exterior enclosure basics defined and understood is the first step. The moral is that you have to understand the basics in order to advance to more sophisticated levels of design performance and execution. This is paramount. For those unfamiliar with the basics outlined above, these principles will be presented initially at a foundation level and then applied to enclosure systems and types later, in the system case study sections. For those who are familiar with these basics, read on. You may find the foundation descriptions useful for their application to the design process discussed in subsequent chapters and the systems/case studies where the basics are applied.

Process

Architectural design is a process-oriented profession and activity. Exterior building enclosure design is also a process. Exterior building enclosures are one of the most visible and technically complex aspects of architecture. Enclosure design intent, performance design principles, system design, fabrication and construction methodologies, and completed exterior enclosures must be studied, researched, and articulated in a meaningful and systematic way or inevitably something will be missed and/or left out. As an architecture student during an interview for a summer intern job, I received some valuable advice when showing my modest portfolio of student work. “You can’t learn it all, you can’t memorize it all, and you will never know it all. What you can do is develop, implement, and practice a problem-solving process.” I have carried this with me during my years of practice.

Enclosure design process has its “Do’s” and “Do Not’s.”

DO’S:

1. Research and continue learning.

2. Listen.

3. Keep an open mind.

4. Accept criticism, and determine what to accept and what to reject.

5. Understand the basics of materials, structural principles, natural elements, natural and human-created forces, thermal transfer and properties, and acoustics.

6. Study manufacturing processes.

7. Distill information.

8. Think with graphics.

DO NOT’S:

1. Do not be afraid to try multiple ideas.

2. Do not be too proud to redesign and redraw.

3. Do not limit your imagination.

4. Do not forget for whom or what the building design and exterior enclosure is designed.

Exterior design is a process that is tailored to the specific needs of the project. In order to be a complete design process, the process must define and answer the five W’s: What, Why, Who, Where, and When, as well as one H: How. This chapter discusses the “What” (basics and topics of exterior enclosures) and “Why” each topic is applicable. For example: What is the extent of the exterior building enclosure? What are the intended functions, and why do they influence design? What are the forces on the exterior enclosure, and what do they influence? What are some of the performance design principles, and why are they applied within enclosure systems and system interfaces? What are some of the types of exterior enclosure systems?

The topics identified are applicable, in part or whole, to all exterior enclosures and their design. These may appear abstract in some cases, until they are applied. Subsequent chapters will address: Who are the participants, and what are their roles? What levels of design are addressed, and when does each occur in the design process? What levels of documentation, collaboration, and coordination occur, and when does each occur in the process? What is expected by builders in the construction process? Why is a particular enclosure system selected, and how is it used? Where are the design basics and performance principles applied to actual case studies? How does it all come together in architecture?

The design process can be creative and lead to innovative solutions faster, and with more joy than pain, if you imagine, research, analyze, collaborate, imagine again, test solutions, refine solutions, document, and execute.

Definition

Prior to initiating a discussion of the basics, it is necessary to define—for the purposes of this book—the exterior building enclosure. It is the enclosing membrane in vertical, sloped, horizontal, or other geometric configurations separating exterior elements and forces from interior occupied areas. The exterior building enclosure begins either at grade or within the height of the building and terminates either on itself or at a roofing system. Roofing systems perform similar functions as the exterior enclosure, but are not described or discussed here. Similar design concepts, principles, design/detailing approaches, and performance functions apply to roofing systems; however, only the interfaces of the exterior building enclosure to roofing systems will be reviewed in this book.

Exterior enclosure systems may be load-bearing or non-load-bearing. A load-bearing exterior enclosure provides enclosure and is also the primary or secondary building structural system. A non-load-bearing enclosure provides a cladding envelope but is not the building primary or secondary structural system. Non-load-bearing cladding systems are often suspended from or contained within and supported by the primary building structural system or other structural supporting elements or systems. Load-bearing and non-load-bearing enclosures are designed to accommodate elements such as air, water, and sun, and withstand applied loads created by natural forces such as wind, seismic, thermal (expansion and contraction), and other forces. Load-bearing and non-load-bearing exterior building enclosure systems must include methods to control and prevent water intrusion, limit air infiltration, admit and control sunlight, control thermal transfer, control acoustics, and perform for a long period of time with minimal maintenance or repair. The term “enclosure system” is a key word and a central concept. An enclosure system is an assembly or combination of parts, components and materials forming a complete or unified whole. An exterior building enclosure is a system made of connections, anchorage components, framing elements, weatherproofing materials, insulation materials and components, and infill materials. All of these materials and components must be researched and understood to ascertain their respective characteristics, strengths, weaknesses, and compatibilities then arranged and ordered in a working combination with principles of physics.

Functions

Whether load-bearing or non-load-bearing, exterior enclosure systems perform multiple functions. While each of these functions can be discussed and reviewed as an individual topic, the multiple functions are interrelated and influence each other. Each exterior building enclosure has primary functions that include:

1. Structural function: The ability of the system to support itself and the applied loads.

2. Weathertightness: Keeping natural elements outside.

3. Energy efficiency: Performing to high levels by reducing energy consumption. Energy efficiency goes hand in hand with weathertightness.

4. Accommodating building movements. This goes hand in hand with structural.

Additional functions, depending on the design requirements, may include acoustics, blast/threat resistance, and other force resistance or performance features.

STRUCTURAL

Owners, architects, engineers, and builders agree that a building is only as good as the strength of its foundation. If the foundation is weak or faulty, the building is doomed. If the foundation is solid and strong, the building will stand for a long time. This concept applies to exterior building enclosure systems as well. The enclosure system must be of sufficient strength and appropriate system depth to support its own weight, accommodate and transfer exterior forces, and span the necessary distances, vertically and horizontally, to supporting building structural elements. In load-bearing conditions, the exterior enclosure system must be of sufficient strength to accommodate the supporting primary building structural demands and transfer applied exterior loads and forces to the foundation. In exterior enclosure cladding applications, the exterior enclosure system must be of sufficient strength to accommodate its own loads (self-weight, often referred to as dead load), applied loads, and forces, and to transfer these through enclosure anchorage assemblies to the primary building structural system. The enclosure must be fully functional during and after the loads are removed. Elements and forces that impose the applied loads are discussed in this chapter.

To withstand exterior forces and support its own loads, the exterior enclosure is designed as a system. The system consists of components, and using the chain analogy, the enclosure structural integrity is only as good as the weakest link or component. Whether the enclosure is an opaque and planar composition such as brick masonry wall (Figure 1.1), a framed masonry natural stone wall (Figure 1.2), or an opaque and transparent composition such as curtain wall (Figure 1.3), the systematic design approach is similar. The structural performance characteristics of each of the components within the system must be understood in order to develop the basic system structural design approach. Materials performing as supports in the system structure have inherent strengths and weaknesses. The goal is to accentuate the strengths and minimize—or eliminate—the weaknesses. Superimposed on the enclosure system is the behavior of the building structural system. Under loading, beams and slabs deflect, columns shorten, and the primary structural frame may “drift” or lean when lateral wind or seismic loads are applied. Primary building structure deflection movements are illustrated by the diagrams in Figure 1.4. Primary building structural movements are covered in mor...