Defining Enclosure

Enclosure Defined
Overview / Lines, Planes, Volumes / Primacy of Structure

Overview
Concerns for sustainability require us to consider the fundamental requirements of buildings and to re-examine our current approaches to environmental separation. Some observers question that perhaps we have gone too far in separating ourselves from nature. If architecture intends to attain sustainability, it is important to start by looking at the idea of enclosure because it drives so many other performance parameters for buildings.

Enclosure has many meanings. It represents a fundamental construct in architectural design pertaining to the representation of spatial arrangements. Through the materialization of basic geometric entities - points, lines, planes and volumes - architecture arranges program across a rich spectrum of expression, ranging from the subtle and suggestive, through to the explicit and absolute. Listening to any discussion of architectural design, virtually all of the terms used to describe spaces, places and their connections are premised on the concept of enclosure.

From an architectural science perspective, enclosure represents a necessary but insufficient condition for effective moderation of the environment, typically indoor for architects and outdoor for landscape architects. For buildings to achieve acceptable, preferably optimal, performance from their envelopes or skins, the principles underlying their performance must be clearly understood. As importantly, the architectural design intent must be sufficiently declarative to guide the selection and manipulation of enclosure elements so that aesthetics are harmonized with sustainability criteria both for the building envelope, and the whole building system.

Enclosures separate one domain or abode from either the outdoors or another domain or abode. It is not necessary for enclosures to provide solid or continuous separation. Enclosure may be accomplished through delineation of various types, but these tend to be expressed through essentially three representations: lines, planes and volumes.

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Buckminster Fuller Geodesic Dome

Lines, Planes, Volumes
A single point does not in itself create a sense of enclosure, however, two or more points connected by a line begin the simplest definitions of enclosure. The goal crease in hockey is an example of enclosure that is well recognized as separating one domain from another. In the built environment, these same concepts are expressed as property lines, and markings on roadways and in parking lots. Primitive cultures used piles of stones and sticks (in some cases adorned with the skulls of their enemies) to delineate territory. Changes in materials, from paving stones to grass lawn, for example, are other means of delineating domains. Lines generally provide the weakest sense of enclosure, but may be the most strongly defended as in the case of private property or political borders.

Basic geometric entities comprise a broad range of enclosure concepts. With the introduction of computers, curvilinear polygons and polyhedra are also attainable.

Planes represent the next level of enclosure in the built environment. Fences, hedges, screens and walls are among the more notable examples of planes that are commonly used in the built environment. Planar elements may be linear, curvilinear or naturally defined by plant materials, and may be continuous or intermittent.

Fences comprised of line elements create planes which enclose property and define domain.

Volumes, or closed shapes created from planar elements which provide both vertical and horizontal separation, tend to provide the strongest sense of enclosure and protection from the elements.

Planar elements may be arranged to define an enclosure which is not necessarily continuous.

The idea of enclosure has a diverse number of cultural interpretations, and has been contextualized in many forms and at many scales. For landscapes, buildings and communities the way in which enclosure is expressed is often fascinating, always revealing.

Architectural enclosures represent our third skin, and often say more about us culturally than our first body skin and our second skin of clothing. This relationship arises from the relativity durability of building enclosures and the social and cultural imposition they imply. As these enclosures agglomerate in the form of human settlements, the extent of their influence on human experience and interaction intensifies, as does their impact on climate and the environment. Ideas of enclosure and their manifestations in artifacts play a large role in explaining the multi-faceted nature of the human species.

Volumetric definition of building enclosure arising from relationships between planar elements that perform various separation functions.

Transitions from public roadway to private property expressed in the language of grass, hedges and a line of trees are as effective as they are pleasing.

Japanese architecture delicately balances intimacy and privacy with access to light and air through operable enclosure elements

Channeling wind by using trees to reinforce the natural topography. In urban areas, our best raceways for cooling summer winds have been surrendered to the automobile.

Enclosures can also be purely recreational and aesthetic, as in the case of this maze created from well manicured hedges.

In some exceptional instances, phenomena such as heat, light, sound or smell are used to define enclosure, or its counterparts, occupancy and territory. For these cases, the separation is somewhat virtual, less concrete. But most of the variations of enclosure that exist rely strongly on the use of materials expressed as lines, planes and volumes. Despite the extensive variety of building enclosures in existence, the tectonics of buildings are relatively few and typical, and are always guided by the need for structural integrity.

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Building enclosure as the sole means of affording privacy and transitional space is depicted in this glimpse of Jodhpur, India.

Primacy of Structure
Requirements for the structural integrity of building enclosures often dominate their form. Building enclosures must be able to resist various forces that act upon their structural systems.

Classification of building loads or forces that must be adequately resisted by the structural system supporting the enclosure.

Forces acting on building can cause several phenomena to occur which are detrimental to structural integrity. They can lead to instability of the structure (collapse, overturning, settlement or translation), and they can lead to local failure of structural members or assemblies. The primacy of structure is evident in all forms of enclosure ranging from linear and planar elements to volumetric expressions of space and place. Even in the case of landscape elements such as earth slopes, retaining walls and plantings, structural considerations cannot be relaxed. Structure in enclosures represents a triumph over natural forces such as gravity and wind, however, enclosures must do more than support themselves. These aspects of enclosure design are presented in the next section on Enclosure Requirements.

In rare cases, structural instability produces distinctive attributes in architectural works, but most building owners would not be appreciative of this level of performance in contemporary buildings.

St. Mary's Cathedral, San Francisco California by Pier Luigi Nervi (and Pietro Belluschi) 1971. Structural considerations drive this distinctive form of enclosure defined by the union of hyperbolic paraboloids.