Density
is a social statistic. It cannot lead the formation of shelter for human activity
within urban areas. It has caused confusion, contradiction, disagreement, and conflict
within and between those in the public and private sectors; but it is now
possible to replace the statistic with a language that can accurately measure the
past, evaluate the present, predict the future, and define decisions in terms
that have the accuracy needed for leadership direction. In order to make my
point, I need to introduce the language, illustrate its leadership potential,
and compare it to the performance of density statistics.
INTRODUCTION
TO THE LANGUAGE
Gross
building area is a fully enclosed square foot area that can be occupied by any
activity. Shelter capacity is the gross building area that can be constructed
per buildable acre available, and there are many options. The amount of gross
building area provided per acre, in addition to the supporting pavement
introduced, is referred to as a level of “intensity”. Intensity is moderated by
the amount of unpaved project open space that remains. At one end of the
spectrum is a small building on thousands of ranch acres. At the other is a
high-rise building on a fraction of an acre. In both cases, the square feet of
shelter and pavement constructed consume land that is a natural source of life.
Activity
is referred to as “land use”. The relationship of shelter capacity and activity
to geographic location affects economic stability and public 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 any urban area.
The
Movement, Open Space, and Life Support Divisions of our Built Domain consume
natural land to serve a Shelter Division that adds to the consumption and is
sprawling without restraint. The square feet of building area and pavement introduced
per acre determines the population and activity that can be served, as well as
the physical intensity introduced. The social open space that remains
contributes to the external quality of life provided. In other words, the
physical, social, and economic characteristics of intensity not only affect the
health, safety, and welfare of a population within The Built Domain; but the
survival of its source of life beyond. We must begin to understand these
relationships.
Six
building design categories encompass most 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 a parking
garage is present, the building is classified by the garage configuration
present. These building categories may be occupied by any activity group that
complies with local building and zoning requirements.
The
point is that shelter classification begins with the building design category
involved, and each category has gross building area limitations defined by
design specification decisions. These decisions limit the scope of land use activity and revenue potential
that can be introduced.
LEADERSHIP
POTENTIAL
Table
1 presents a set of optional decisions for the G1 Design Category. They are represented by the specification values
entered in the boxes of its Land and G1 Modules. There are fifteen specification
boxes and each value represents a design decision that can be adjusted to
explore shelter capacity alternatives. The equations in Col. H of Table 1
convert specification decisions to implications in Col. G. The objective of the
algorithm is to distill the core buildable land area available in cell F32.
The
master equation in cell A37 correlates the core area found in cell F32 with the
parking decisions entered in cells F33 and F34 and the floor quantity options
entered in cells A42-A51. It predicts gross building area alternatives in cells
B42-B51 based on these floor quantity options. The remainder of the Planning
Forecast Panel predicts additional implications related to the gross building area options in Col. B
using the secondary equations on line 41. Shelter capacity options corresponding to the gross building area options forecast in Col. B are listed in Col. F. The entire panel illustrates a few of
the many implications that can be forecast as a function of gross building area
predictions. Revenue, expense, construction cost, return on investment, population, and traffic generation are a few that are not shown.
Table
1 illustrates the many specification decisions required to calculate shelter
options for the G1 Design Category. A change to one or more values entered in
the boxes of Table 1 would produce a new forecast in Col. B of the Planning
Forecast Panel, and hundreds of options could be predicted in less time than it
would take to produce one sketch.
The
unpaved open space percentage specification in cell F11 of Table 1, and the
impervious cover limit calculated in cell F12, represents one of the decision /
implication relationships that play a significant role in the calculation of
shelter capacity options. An unpaved open space decision, however, is only one
of many design decisions that combine to determine shelter capacity options.
Open Space
It’s
easy to overlook open space because its value to our quality of life is
currently a function of subjective opinion, and this opinion can reduce private
return on investment. It is an inevitable conflict, but one open space decision
has already been made that is unrecognized by most.
Unpaved
open space protects storm sewer capacity from excessive runoff. Storm water runoff
is produced by impervious cover and re-directed by storm sewer capacity.
Capacity is expressed as the percentage of impervious cover that can be
accommodated by a given pipe size. Subtracting this percentage from 100 yields
the amount of unpaved open space expected, unless more intricate civil
engineering solutions are introduced. A greater pipe size can accommodate a
greater percentage of impervious cover, but the pipe cost increases as well. A
developer often attempts to minimize cost by minimizing pipe size. This reduces
the impervious cover percentage that can be accommodated, but the limit is
often over-looked by decision-makers for any number of reasons. If an
impervious cover limit is exceeded by many along a branch storm sewer line, unpaved
open space declines and flooding is an inevitable consequence, unless detention
solutions are introduced. Flooding can easily occur when a community does not
know the impervious cover capacity of each branch line in its storm sewer
system and approves building and pavement additions over years based on the
assumption that growth is good. Unfortunately, the unpaved open space
percentage required to protect storm sewer capacity may not be adequate to
protect the neighborhood’s quality of life.
Shelter
Capacity and Intensity
The
gross building area options forecast in Col. B of the Planning Forecast Panel of
Table 1 were used to produce the shelter capacity options in Col. F and the
intensity options in Col. G. These intensity levels are like the first blood
pressure readings. I can only hope that continued measurement and evaluation
will produce intensity knowledge and parameters that can lead to an improved quality
of life.
Intensity
options are produced by values entered in a design category specification
template. A leadership decision is taken by defining the design category and
specification values adopted for a given location.
Design
category choices and specification decisions have gross building area implications.
Gross building area divided by buildable land area is shelter capacity. The
ability to accurately define gross building area options with a design category
master equation makes it possible to predict many implications that are
functions of the square foot options predicted.
Urban Form
Building
arrangements are often referred to as massing compositions. A collection of
compositions is referred to as urban form. Ideally, a plan for urban form allocates
the Shelter, Movement, Open Space, and Life Support Divisions of The Built
Domain to serve growing populations within geographic limits that protect their
quality and source of life – The Natural Domain.
Master
equations make it possible to measure, 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 design categories
and specification values chosen to create urban form. Our quality of life is
affected because we must live within and among the buildings, pavement, spaces,
and movement systems we create.
Several
Shelter Design Principles
Table
1 is based on 40% unpaved open space in the buildable land area. When the gross
building area values in Col. B of the Table 1 Planning Forecast Panel are
mapped in Figure 1, the results can be expressed in the following terms:
The rate of increase in gross building area declines at an
accelerating rate as the number of building floors increase in the G1 Design
Category.
Building
cover declines more rapidly than gross building area increases because the
gross building area permitted per parking space (a) in Table 1 is less than the
parking lot surface area planned per parking space (s).
Figure
1 illustrates the dramatically decreasing rate of increase in gross building
area as building height increases. Gross building area increases from 38,577
sq. ft. to 59,000 sq. ft., but it barely increases above the five story mark of
55,722 sq. ft. This occurs because gross building area does not increase as
rapidly as surface parking area when (a) is less than (s). Expanding parking
area for additional spaces is required to justify increased building area, but
this eventually reduces the land remaining for building cover to unrealistic
levels.
Figure
2 is based on (a) being greater than (s) and 15% unpaved open space being
entered in Table 1. Figure 2 shows that gross building area still increases at
a decreasing rate, but the results produced are dramatically different because
of the specification value changes. Gross building area increases from 85,630 sq.
ft. to 186,152 square feet, but gross building area slowly increases above the
5 story mark of 164,673 sq. ft. Parking cover consumes the same amount of land
per space, but gross building area per parking space grows more than parking
lot area per space. This scenario explains why the gross building area arc
increases more rapidly than the building cover arc declines in Figure 2.
When
the five story gross building area potential in Tables 1 and 2 is subtracted
from the one story gross building area potential predicted, the results expose another
design principle. 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. This observation produces the following principle.
The most
rapid increase in G1 gross building area occurs within a 1-5 story range.
The
actual gain from 1-5 stories is a function of all design specification
decisions entered in Table 1. Above 5 stories, the gross building area gain per
additional floor becomes increasingly less cost-effective.
Figure
2 produces much greater gross building area potential, but is the open space
and parking reduction desirable? I won’t attempt to answer the question. I’m
simply pointing out an issue that can be accurately measured and evaluated with
comparative studies using the language of City Design. In fact, the complete
language of City Design can be used to measure existing conditions, evaluate
future potential, and accurately define leadership decisions with confidence
based on objective measurement and comparative evaluation.
Figures
1 and 2 explain why the gross building area permitted per parking space (a) and
the unpaved open space percentage proposed per project (OSAU) are two of the
most common points of public and private disagreement. Greater open space and
parking requirements reduce potential gross building area and private return on
investment, but at what point do the reductions produce excessive intensity in
the neighborhood? This cannot be answered without a comprehensive method of
measuring and evaluating existing conditions. It cannot be improved without an
accurate method of converting measurement and evaluation to accurate,
comprehensive, and correlated leadership expression. A new language of city design
is needed. I’ll get to this in the final section of this essay.
The
G1 design principle behind this section of the essay can be stated in a single
sentence.
Every additional
surface parking space justifies increased gross building area; but reduces the
core land area available for building cover, until the core area remaining
becomes too small to accommodate a realistic floor plan.
Figures
1 and 2 demonstrate that planning and design issues can be expressed in
mathematical terms. This has the power to persuade in a political environment
of conflicting opinion. 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. The answers we find
will be reflected by the context, composition, and function of urban form. The
appearance of these solutions will symbolize our progress toward the symbiotic correlation
of Shelter, Movement, Open Space, and Life Support within a geographically
limited Built Domain that protects our quality and source of life – The Natural
Domain.
COMPARISON TO
DENSITY
Density
is a statistic that indicates the number of residential dwelling units provided
or permitted per acre of land occupied. The gross building area potential of
the land given the combined effect of all zoning regulations is ignored because
accurate calculation has been elusive, but feasibility is a function of the
relationship between dwelling unit quantity, unit area, and gross building area
potential. A density statistic cannot provide the correlation required for
adequate leadership.
Table
1 has illustrated the correlated design specification items, topics, and master
equation that produce gross building area options per buildable acre for the G1
Design Category. A feasible density is one that multiplies dwelling unit area
by quantity to fit within the gross building area potential of a given land
area. Density does not lead to the gross building area potential of land. It is
limited by the specification decisions that determine gross building area, and
unachievable density regulations or goals simply introduce confusion and
frustration.
Density
is oblivious to the inter-active design specification decisions in Table 1, but
they determine gross building area potential and intensity implications for any
given land area. It is also oblivious to the various dwelling unit area
decisions that can increase or decrease density within gross building area potential.
The conflict between ambiguous density regulation, uncorrelated zoning
regulation, and the gross building area potential of land is often inevitable.
CITY DESIGN
The
creation of urban form begins with an ability to predict gross building area
capacity, intensity, and activity options for every land area and location
within the geographic area defined.
Our
current inability to correlate the realistic gross building area potential of
land with the activity permitted and quality of life desired produces
confusion, conflict, and suspicion that can only be resolved with opinion and
compromise. This often produces arbitrary decisions and unsatisfactory results that
assemble over time.
The
gross building area options produced by correlating the design specification
decisions in Table 1 could not have been produced by an independent density
statistic. The observations produced by charting the Table 1 options in Figures
1 and 2 would remain unknown or intuitive at best. There are just too may
design decisions involved that affect and precede density calculation and can’t
be led by a density statistic. It is not a credible minimum design standard
capable of consistently leading shelter capacity toward urban form capable of
increasing capacity and improving our quality of life. It is a rear view mirror,
not a heads-up display of options and opportunities.
I
have written The Science of City Design to explain design categories,
activity groups, design specifications, architectural algorithms, master
equations, and planning forecast panels. These topics introduce a vocabulary
and language of city design that can consistently improve planning results by
correlating the decisions required to shelter growing populations within a
limited Built Domain. The goal is to protect this population’s quality and
source of life.
For
those interested in pursuing the study of city design, urban form, and its
physical, social, psychological, environmental, ecologic, and economic
implications; The Science of City Design can be found at Amazon.com in
e-book and paperback versions.
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