NOTE 1: This essay was originally published in September, 2010. This revision is based on the information provided in the book entitled, The Science of City Design, by Walter M. Hosack, 2016 and available from Amazon.com. The equations presented are new and the differences are significant.
NOTE 2: All figures and tables are located at the end of the text.
The development capacity of land is equal to the gross building area that can be constructed per shelter acre available. (Shelter area is calculated in cell F and G17 of Table 1.) Gross building area is a volume that can be occupied by one or more activities given the floor quantity chosen. The percentage of building cover and pavement cover provided per acre is referred to as “intensity”. Intensity is offset by the percentage of unpaved project open space provided. At one end of the intensity spectrum is a small building on thousands of acres. At the other is a high-rise on one acre. In both cases, the square feet of shelter and pavement constructed per acre of land involved is an indication of the physical intensity introduced.
Activity is referred to as “land use”. The relationship of shelter capacity, condition, and social activity to geographic location affects economic stability and social acceptance. In other words, shelter capacity, condition, and location produce levels of physical intensity, social activity, and economic contribution that affect our quality of life within The Built Domain.
The Movement, Open Space, and Life Support Divisions of our Built Domain convert and serve land for the Shelter Division. The square feet of building area and pavement introduced per acre determines the population that can be served, the scope of activity that can be conducted, and the economic contribution that can be expected. The social open space that remains contributes to the quality of life provided within The Built Domain. In other words, the physical, social, and economic characteristics of intensity not only affect the physical, social, psychological, environmental, and economic welfare of a population within The Built Domain; but the survival of its source of life beyond.
Six building design categories encompass most, if not all, of the shelter provided on the planet. They are:
1) G1: Buildings with surface parking around, but not under the building
2) G2: Buildings with surface parking around and/or under the building
3) S1: Buildings with structure parking adjacent to the building on the same parcel
4) S2: Buildings with underground parking
5) S3: Buildings with structure parking at grade under the building
6) NP: Buildings with no parking required
The parking structure options may have supplemental surface parking, but when present, the building is classified by the parking garage configuration present. These building categories may be occupied by any activity group that complies with the local building and zoning codes. The point is that shelter classification begins with the parking design category involved, and each category has shelter capacity limitations that are dictated by parking design specification decisions. For instance, parking design specification decisions have been entered in cells F33-34 of Table 1. Twenty-three other decisions have been entered in the remaining specification boxes of Table 1.
A set of optional percentage decisions are illustrated by the values entered in the boxes of the Land and G1 Modules of Table 1. There are fifteen boxes and each value entered in a box represents a design decision that can be modified to test options. The equations in Col. H of Table 1 convert these decisions to square foot area implications in Col. G. The objective of the algorithm is to identify the shelter area available in cell F17 and the core buildable land area available in cell F32.
The master equation in cell A37 correlates the specification data entered and calculated in the Land and G1 Modules of Table 1 with the floor quantity options entered in cells A42-A51. Shelter capacity alternatives are predicted in cells B42-B51 of the Planning Forecast Panel. The remainder of the panel predicts the implications of the shelter capacity forecasts in Col. B using the secondary equations on line 41. This panel illustrates a few of the many implications that can be forecast as a function of a gross building area prediction.
Table 1 illustrates the 16 decisions required to expose options and lead the G1 Design Category toward a desired objective. A change to one or more of the specification values in Table 1 will produce a new forecast of options in Col. A of the Planning Forecast Panel, and hundreds of options can be predicted in a very short time. The point here is that the gross building area predicted can be occupied by any permitted activity, and that a single density requirement is not a substitute for the 16 decisions required to lead performance toward a desired objective.
The gross building area options forecast in Col. B of the Planning Forecast Panel are used to produce the shelter capacity forecast in Col. F. These capacity options are used to calculate intensity, intrusion, and dominance measurements in Columns H and J. These four measurements are like the first blood pressure readings. They indicate the impact level present or proposed. I can only hope that continued measurement and evaluation will lead to impact parameters that can improve urban health, safety, and welfare.
Intensity options are defined by stating the design categories and specification values being considered. A leadership decision establishes an objective by defining the design category and specification values selected for further architectural definition and context refinement. Before refinement, however, the impact selection and its 16 specification decisions represent a massing definition. When massing compositions are combined, the product is referred to as urban form; and a plan for urban form determines the shelter capacity of a Built Domain. Design specifications and impact measurements make it possible to evaluate, diagnose, and prescribe urban form one project at a time. When a Built Domain is geographically limited, the quality of life within these limits will be a function of the definitions chosen in relation to the population size involved -- and the natural environment preserved.
A DESIGN PRINCIPLE
The G1.L1 equation in Table 1 reveals a design principle when the gross building area values in Col. B of the Planning Forecast Panel of Table 1 are mapped. It can be formally expressed in the following terms:
When the G1 Design Category is considered, the rate of increase in gross building area declines at an accelerating rate as the number of building floors increase.
Figure 1 illustrates this principle and clearly shows the dramatically decreasing rate of increase in gross building area as building height pushes above five floors. Figure 1 is based on the provision of 40% open space. If this were reduced to 15%, the efficiency profile in Figure 1 would show the same rapidly decreasing rate of increase in development capacity, but start at a higher point on the Y-axis. In fact, any change to design specification values will alter the intensity and context created, but its impact remains a matter of opinion because it has not been measured and evaluated.
Figure 1 confirms the intuition of many designers and converts this intuition to knowledge that is a function of the Table 1 forecast model. The context implications of design specifications, including open space requirements, and the intensity options produced remain to be explored; but there is another point to be made. Figure 1 demonstrates that planning and design issues can be expressed in mathematical terms. This has the power to persuade in a political environment that cannot be avoided. It also improves our ability to collaborate with the science of others; since the land our planet can donate to shelter, and the shelter capacity of this land, is becoming an issue of survival.
Figure 1 was based on the gross building area permitted per parking space (a) being less than the gross area estimated per parking space (s) and 40% unpaved open space. This is not always the case, and Figure 2 is based on (a) being greater than (s) and 15% unpaved open space. The design principle still applies, but the results produced are dramatically different when these values are modified. A comparison of these results should explain why the gross building area permitted per parking space and the impervious cover proposed are two of the most common points of public and private disagreement.
Figure 2 shows that gross building area potential is significantly increased when (a) is greater than (s). The rate of gross building area increase has not flattened out at 10 stories, and gross building area potential begins at 85,630 sq. ft. rather than 38,577 sq. ft. When surface parking is planned or required, however; the risk of inadequate parking space quantity is significantly increased when (a) is greater than (s).
When the five story gross building area is subtracted from the one story gross building area in each figure, the differences become more apparent. In the case of Figure 1, the total gain for 1-5 stories is 17,145 sq. ft. The total gain for 5-10 stories is 3,278 sq. ft. In the case of Figure 2, the total gain for 1-5 stories is 79,043 sq. ft. The total gain for 5-10 stories is 21,749 sq. ft. Above 5 stories, the gross building area gain per additional floor declines and becomes increasingly less cost-effective in both cases.
Figures 1 and 2 document a relationship we have intuitively understood for quite some time. Greater parking space requirements (a) and greater parking areas per space (s) reduce the area available for building footprint and unpaved project open space. This reduces gross building area potential. Unpaved open space is consumed to increase parking areas and gross building area options. (Gross building area may be occupied by any residential or non-residential activity.) Parking variances are sought to reduce the parking requirement (a) when open space consumption does not provide enough additional parking to justify a gross building area objective. (There may be no objective. It may be a simple attempt to maximize gross building area potential given the cost of the land.)
Parking requirements have little research to defend them and can easily be challenged by the experience of a current applicant’s operations. Unfortunately, successful appeals can leave deficient parking for a future building owner. In the worst cases, it can contribute to economic decline, deteriorating condition, and inadequate public revenue from the acres consumed within a city’s boundaries.
Figures 1 and 2 are based on the design specification data in Table 1. The (a) value in Table 1 has been modified to produce Figure 2. The example illustrates the influence of parking requirements on gross building area potential, but this is not the underlying point of the discussion.
The results in Table 1 could not have been predicted by a residential density regulation; and if they cannot be predicted, they cannot be led to produce results that avoid excess and decline. Table 2 lists the design categories and forecast models that can enable us to speak in the language required to lead shelter toward solutions that protect our quality of life within a geographically limited Built Domain that protects our source of life. In other words, residential density is a product of design specification decisions. It does not make them nor provide design leadership. Table 3 presents a Built Domain classification system that incorporates the generic design categories of Table 2.
Our ability to shelter populations and activities within a limited built environment will depend on our ability to balance the artificial world of our presence with the natural world of our planet; and on our ability to balance a growing population with the average intensity required. This is an emerging awareness tormented by conflicting opinion; but fortunately, intensity and impact can be predicted. The options forecast however, have context implications that remain to be explored; and research is required to avoid the oppression intensity and impact can produce.
The prediction of shelter options will improve when we can quickly forecast the entire spectrum of intensity alternatives that meet an open space specification; since open space offsets intensity and is the weight that produces balance within our built environment. It is also the foundation of a natural environment that suffers our presence at its discretion. In other words, it is all about design with space – since open space must be present before details can be introduced -- and success will depend on our ability to forecast the implications of intensity options that preserve its presence. We have learned however, that simply adding open space is not an answer; and we need a scientific method that can measure context, evaluate implications, forecast alternatives, and express decisions in precise terms. At this point, vocabulary will become language with the power to lead the shape and form of our built environment to the limits demanded by its silent partner -- and to the quality of life deserved by its inhabitants.
Architecture has always sheltered the activities of its period and been a product of the knowledge and opinions available. It is no accident that the current sprawl of architecture reflects our confused relationship to the land. Opinion has produced indiscriminate regulation and the land is compromised by the process. We are distracted by the details of compatibility, construction and appearance — not to mention ownership and sovereignty; but intuition is looking beyond the environment we build to include the environment we consume. Balancing these two worlds will depend on our ability to understand impact and offer options within limits that meet our strategic goals.
Architecture, landscape architecture, city planning, and regional development have borrowed from the knowledge of others, but need a common language with greater ability to coordinate the efforts of many while multiplying success over time. Until then, the language of others will continue to substitute opinion for knowledge in the search for leadership of the built environment. The goal is to prevent this artificial presence from consuming a natural gift that constantly adjusts in reaction to a universe of forces. Our responsibility is to recognize that cities are one of the forces to be reconciled, that the shelter we build reflects the level of awareness we achieve, that shelter within limits requires an improved understanding of the intensity and impact options involved, and that symbiotic survival is the goal. Intuition is again required – and leadership is needed when anticipation must substitute for proof.
Struggles for freedom establish new relationships among men, but over-simplify their relationship to a planet within a universe that is a gift from infinity. We may be free to own the land, sea and air, but we are not free to abuse it and its inhabitants in the silent court that prevails. Our knowledge is limited, our vocabulary is inadequate, and our language is ineffective; but our vision must restrain an instinct to control or be dominated that has become a threat to the planet. It is time to follow the road from intuition to science again; and many sciences must collaborate to lead the shape, form, and intensity of cities toward the harmony needed. Density is not equal to the leadership required. It does not control the team of horses involved and must be replaced with algorithms that can correlate the forces in play. Nothing less than symbiotic survival is at stake, and we must again prove that we are equal to the threat success has produced by providing the leadership required.