The search for a scale that can measure the level of pressure imposed by shelter, movement, open space, and life support within the projects, neighborhoods, and districts of our urban world continues. I believe this human scale has at least five measureable components; and that they combine to give an initial indication of urban health within the urban anatomy. These factors and terms are relatively unknown, so let me begin with an explanation.
Shelter capacity (SFAC) is the gross building area (GBA) in sq. ft. provided per buildable acre (BAC) to shelter any activity. We tend to refer to buildings by the activity within, such as a bank building; but a building can be remodeled to suit many activities. The significance of the building is the amount of land it consumes per thousand sq. ft. of gross building area, since this is land removed as a source of life.
SFAC = GBA / BAC
Building capacity is a measureable factor that can be multiplied by a surface pavement percentage to produce an intensity measurement, but the impact of the measurement must be evaluated in addition to three other factors that combine to affect our physical, social, psychological, environmental, and economic quality of life. Like the first blood pressure readings, however, these measurements will have little meaning until evaluated correlated within a database of accumulated research.
Shelter capacity produces building mass. In this context, the first sentence in this section can be rewritten to say that the product of building mass times the percentage of impervious pavement present in a buildable land area is a measurement of physical intensity. Building mass is represented in this context by a massing ratio equal to shelter capacity per acre (SFAC) divided by one acre in sq. ft. to make the calculation a manageable statistic. In mathematical terms:
MAR = SFAC / 43,560
INT = MAR * IMP%
The Theory of Relative Intensity
A range of potential building mass values has been placed along the y-axis of Table 1, but the ratios do not indicate the impact of related two-dimensional pavement. Impervious cover ratios are represented in ten percent increments of buildable land area along the x-axis to complete the matrix. When an impervious cover percentage is multiplied by a massing ratio, the result is a level of intensity within a given buildable land area (BLA). Table 1 presents the entire range of shelter intensity options available to planners, architects, and designers in a single table. The fact that a value is in the upper left hand quadrant of Table 1 does not automatically mean that it is desirable, however. Table 1 simply defines the entire spectrum, and many options are undesirable. The challenge is to measure, evaluate, identify, and locate existing success and failure within the table.
Shelter capacity is produced by six shelter design categories that can be occupied by any permitted activity. These categories comprise the Shelter Division of The Built Domain and are listed Table 2. Three examples of the residential activity group are shown below these design categories to illustrate the relationship between a design category and an activity group. The classification illustrated is part of the language needed to pursue the science of city design, and begins with the recognition that there are two worlds on a single planet: The Natural Domain and a Built Domain that contains Shelter, Movement, Open Space, and Life Support Divisions.
Informed annexation and land use allocation can only occur when there is a mathematical ability to correlate the shelter capacity options for land with the economic yield implied by potential activity per buildable acre. When correlation becomes feasible, land use allocation, capacity, and intensity options for economic security will become a subject of digital planning and evaluation. The knowledge gained will give planners the credibility to persuasively debate the issue and pursue new revenue that is not based on old assumptions, opinions, and mistakes.
Intrusion (INTR) is a calculated value used in a building dominance calculation (DOM). It is building height in floors (f) divided by five to avoid the unwieldy calculations produced by skyscraper heights. (When there are two or more buildings in the same project area, varying heights must be weighted to reflect the composition.) Intrusion is introduced as a calculation because a taller building is considered to be more intrusive when all other site planning topic values are equal.
Shelter dominance (DOM) is the sum of shelter intensity (INT) and intrusion (INTR) within a project, neighborhood, or district. In mathematical terms:
DOM = INT + INTR
When the constituent topics of intensity and intrusion equations are substituted in the dominance equation above, it becomes:
DOM = ((SFAC / 43,560) * IMP%) + (f/5)
In more general terms, shelter dominance within a project, neighborhood, or district land area is a function of: (1) the buildable land area available; (2) the gross building area constructed; (3) the percentage of buildable land area occupied by impervious cover; and (4) the building height introduced.
Table 3 has been created to illustrate the spectrum of potential building dominance options. Intensity options are arranged along the y-axis and intrusion options are arranged along the x-axis. Adding the two options produces a matrix of dominance values that represent the spectrum of design options available, and not all are desirable. The challenge is the same as that presented by the intensity matrix in Table 1. Existing success and failure must be measured, evaluated, identified, and located in the table.
Impact is the correlation of traffic with shelter dominance in an urban area. A traffic ratio (TRR) is equal to the average daily traffic (ADT) in a neighborhood block divided by 1,000 to make the statistic manageable. Impact is measured by adding a shelter dominance measurement to a traffic movement statistic. In mathematical terms:
TRR = ADT / 1,000
IMPACT = DOM + TRR
IMPACT = ((SFAC / 43,560) * IMP%) + (f/5) + (ADT/1,000)
In other words, if you can calculate shelter capacity and impervious cover, you can calculate the shelter intensity present on a given buildable land area. If you know intensity and building height, you can calculate building dominance. If you have calculated building dominance and know the average daily traffic present or predicted adjacent to the land area, you can calculate physical impact. (A larger number indicates greater impact.)
An impact measurement includes capacity, intensity, intrusion, dominance, and movement statistics. The spectrum of possibilities represents a graduated human scale that can indicate the health of an urban area in relation to the surrounding activity present. The actual spectrum raises a fundamental question for further research:
What impact limits are needed to protect our physical, social, psychological, environmental, and economic quality of life within a geographically limited Built Domain that is economically stable and ecologically symbiotic?
Answers to this question will begin to define the context, composition, pattern, and appearance required to protect a growing population’s source and quality of life. Answers must be found because Mother Nature simply does not compromise with ignorance.
The decisions we make concerning the shelter capacity of land is a first tier consideration. It affects the composition, context, and capacity of the cities we inhabit and the scope of land removed from its symbiotic purpose. The activity that takes place within shelter capacity, and the surrounding relationship of these activities, varies as building occupancy changes. This physical and social equation adjusts at a very slow pace, but we have enough experience to know that they can affect a city’s psychological, environmental, and economic vitality when they cannot be forecast to prevent a declining quality of life.
Up to this point the discussion has focused on the measurement of existing conditions. The objective, however, is to learn from these conditions; to repeat success; and to avoid failure. This means that we must be able to use the knowledge gained to lead future policy, strategy, tactics, and performance. Table 4 is included to explain how this can be accomplished using the G1 Design Category as an example.
The G1 Category includes all buildings with surface parking around, but not under the building. It seems to be the most popular shelter category in use today, and is occupied by a wide range of activities with an equally wide range of economic potential. The purpose of this example is to demonstrate how shelter capacity options for a given land area can be accurately predicted. This forecasting potential is the key to strategic city design evaluation and decisions that can be specified with the item values adopted in a design category forecast model.
In other words, shelter category and capacity decisions come first. They establish the composition and context of an urban pattern that must be designed to protect our quality of life. Occupancy determines the economic potential of the shelter resource provided.
Gross land area is given in cell F3 of Table 4 and shelter capacity options (GBA) are predicted in Column B of the Planning Forecast Panel based on the building height alternatives in Column A. The values entered in the boxes of the table represent the design decisions that were correlated to produce the forecast. This template should make it clear that a single value cannot hope to lead to the results predicted.
A change to any value in any box of the template would produce a new forecast. The values predicted in Columns C-G of the Planning Forecast Panel are functions of the shelter capacity predictions in Column B. They are a small sampling to the predictions that can be made once the shelter capacity options in Column B can be forecast. For instance, construction cost, population, traffic generation, and the economic implications of occupant activity are just a few of the predictions that are a function of the square foot options forecast in Column B of the Planning Forecast Panel.
The values entered in the template specification boxes of Table 4 represent a definition of human scale. There are 15 specification boxes and 10 building height alternatives that can be evaluated for a total of 25 optional design decisions. Measured values from an existing project could also be entered in these boxes for evaluation. The intensity levels calculated in Column G of the Planning Forecast Panel present the implications associated with these decisions. They are like blood pressure readings without a frame of reference, however. The condition of the patient cannot be placed in perspective.
At the present time Table 4 represents potential. It is not an answer but part of a vocabulary and language that can be used to search for graduated levels within a human scale that will protect our quality and source of life. I won’t discuss Table 4 and its design category companions in greater detail because they are covered in my new book, The Science of City Design. It is available in e-book and paperback from Amazon.com. The book is my attempt to expose the potential to define human scale in terms that can define past decisions and lead to a symbiotic future.
THE SYMBIOTIC IMPERATIVE
When the architect Louis Sullivan mentioned that form follows function he was actually referring to a fundamental organic principle, in my opinion. His student, Frank Lloyd Wright, adopted the concept and referred to “organic architecture”. I believe they were both pointing to a symbiotic imperative that they could only express at the time with fine art. I’ll repeat Sullivan’s poem here and let you draw your own conclusions.
"It is the pervading law of all things organic, and inorganic,
of all things physical and metaphysical,
of all things human and all things super-human,
of all true manifestations of the head, of the heart, of the soul, that the life is recognizable in its expression,
that form ever follows function. This is the law."
Louis Sullivan, 1896
The phrase “form follows function” was interpreted during the Industrial Period to mean that the function of an invention is reflected by its form and appearance, but this led us to overlook the symbiotic imperative that rules our presence on the planet. It would not have been so easy to overlook if the last line in Sullivan’s poem had read, “that form ever follows (symbiotic) function. This is the law.” We began converting and consuming the land with our inventions, and recognized that the forms and objects we created were a function of the purpose we defined. It was easy to assume that we took precedence over the symbiotic imperative until ecological failure began to appear.
We will not correlate our presence on the planet with its symbiotic imperative overnight, but I believe most of us recognize that we cannot consume the planet with a blanket of sprawling pavement, or co-opt its natural functions, and survive. The form of shelter capacity, intensity, and dominance is one issue. It affects our ability to live within a limited Built Domain that protects our quality and source of life – The Natural Domain. The symbiotic function of The Built Domain is a separate issue. Both must be solved. There is no option. This is what Sullivan meant when he said, “This is the law”. Cities will not flower until they build symbiotic roots. The human scale is a contribution to the growing number of tools that can be used to build knowledge and lead city design toward the goal.