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Zoning regulations address individual issues and produce random results within a built environment that must provide shelter for growing populations within sustainable limits. The definitions of dwelling unit and buildable area illustrate the point; but the point is applicable to the entire concept of zoning, which is a legal nod to the sprawling issue of shelter from an unstable environment.
Zoning regulations address individual issues and produce random results within a built environment that must provide shelter for growing populations within sustainable limits. The definitions of dwelling unit and buildable area illustrate the point; but the point is applicable to the entire concept of zoning, which is a legal nod to the sprawling issue of shelter from an unstable environment.
At the present time, dwelling unit quantity is found by multiplying the acres involved by the number of dwelling units permitted per acre; but dwelling unit area and acre are often ambiguous. This means that a “dwelling unit” can be any size and the number of “acres” can include the total land area, even when some of it is unbuildable. This can leave too many dwelling units squeezed on a “buildable area” that is a fraction of the total land involved; or it can leave a permitted number of units with too little space remaining for the parking and open space needed. This defeats the concept of density, which is to limit building mass and pavement on the land we occupy for shelter. Parking is often considered open space in these circumstances. If too many dwelling units remain, requests to reduce parking requirements are submitted and intensity continues to increase. This is encouraged because the realistic development capacity of the land could not be forecast, and was rarely equal to the density permitted.
A realistic number of dwelling units is based on the buildable land available, the average dwelling unit area involved, the parking and loading required, the miscellaneous pavement anticipated, the open space expected and the building height permitted. These factors influence achievable density, and optional values can now be entered in design specification templates to forecast development capacity and intensity alternatives.
All specification templates for all design categories begin by calculating the “buildable area” and “core area” involved, since these areas must be known to accurately forecast development capacity for any gross land area. Buildable area in these forecast models is equal to the gross land area GLA minus percentages for present or planned public rights-of-way RDA and unbuildable areas UNB such as, but not limited to, ponds, wetlands, ravines and unstable soil. In other words, BLA = GLA – ((RDA% + UNB%) * GLA). Core area CORE is the buildable land area available for building footprint BCA and parking area after percentages of the BLA have been subtracted for project open space S, miscellaneous pavement MSP and loading areas LDA. In other words, CORE = BLA – ((S% + MSP% + LDA%) * BLA). This is the area that determines realistic shelter capacity when combined with building height options. It is found after a conscious provision for open space S has been subtracted. In the past, S has been a function of setback requirements, but too many zoning ordinances permit setback areas to be used for parking. This makes the ordinance a game rather than a plan for our quality of life.
Core area sets the stage for development capacity and intensity. (Reminder: development capacity means the gross building area GBA present per buildable acre. Intensity is project open space per sq. ft. of development capacity.) It’s not hard to imagine that a given land area will accommodate more dwelling units if the open space and parking requirement is less. This makes arguments over parking, setbacks and permitted dwelling units inevitable – when capacity and intensity cannot be accurately predicted. In these cases, open space is often sacrificed to accommodate unrealistic density expectations encouraged by impractical zoning ordinance provisions.
Within the core, multi-family residential development capacity is inversely proportional to the aggregate average dwelling unit area AGG provided -- when all other design specifications are held constant. Table 1 has been removed from the design specification template of forecast model RG1L to explain the AGG value. It shows how the average dwelling unit area AGG of a project is a function of the dwelling unit types DU, dwelling unit areas GDA, dwelling unit mix MIX and building efficiency (e) values chosen. Building efficiency is a factor because AGG is equal to the gross building area divided by the number of dwelling units provided. This means that building support areas must be accounted for in its calculation. These support areas include, but are not limited to, circulation areas, mechanical rooms, wall thickness, etc. The ratio of net dwelling unit area to gross building area is referred to as building efficiency. The comprehensive dwelling unit area CDA calculated in Table 1 increases each GDA value to account for the support areas anticipated by the building efficiency percentage (e) entered. The result is a forecasted AGG value. The total building area permitted per parking space (a) is also calculated based on the parking requirement (u) entered at the top of the table.
TABLE 1 DEFINING AN AVERAGE DWELLING UNIT (AGG)
Parking lot spaces planned or required per dwelling unit | u= | 1.5 | |||||||||||
Garage parking spaces planned or required per dwelling unit | Gn= | 0 | |||||||||||
Building efficiency as percentage of GBA | |||||||||||||
e= | 80% | must have a value >0 entered | |||||||||||
Bldg. support as fraction of GBA | Bu= | 20% | e + Bu must = 1 | ||||||||||
Dwelling Unit Mix Table: | |||||||||||||
DU | GDA | CDA=GDA/Be | MIX | PDA = (CDA)MIX | |||||||||
dwelling unit type | gross du area | comprehensive du area - including support | du mix | Pro-rated du area | |||||||||
EFF | 350 | 438 | 10% | 44 | |||||||||
1 BR | 500 | 625 | 30% | 188 | |||||||||
2 BR | 1,000 | 1,250 | 60% | 750 | |||||||||
3 BR | 1,200 | 1,500 | 0% | 0 | |||||||||
4 BR | 1,400 | 1,750 | 0% | 0 | |||||||||
AGGREGATE AVG. DWELLING UNIT AREA | (AGG) = | 981 | |||||||||||
GBA sf per parking space | a= | 654 | |||||||||||
Enter zero in the adjacent box unless you wish to override the AGG value calculated above | 0 | ||||||||||||
The data shown in bold within boxes in Table 1 are design specification values that can be modified to explore options. Table 2 illustrates another MIX option. It should be clear from these tables that the AGG values simply represent an average of the dwelling unit mix proposed and building efficiency estimated. The building area (a) permitted per parking space increases in direct proportion to an increasing AGG value since the parking spaces required per dwelling unit remain constant for any dwelling unit MIX contemplated.
TABLE 2 DEFINING AN AVERAGE DWELLING UNIT (AGG)
Parking lot spaces planned or required per dwelling unit | u= | 1.5 | |||||||||||
Garage parking spaces planned or required per dwelling unit | Gn= | 0 | |||||||||||
Building efficiency as percentage of GBA | e= | 80% | must have a value >0 entered | ||||||||||
Bldg. support as fraction of GBA | Bu= | 25% | e + Bu must = 1 | ||||||||||
Dwelling Unit Mix Table: | |||||||||||||
DU | GDA | CDA=GDA/Be | MIX | PDA = (CDA)MIX | |||||||||
dwelling unit type | gross du area | comprehensive du area – including support | du mix | Pro-rated du area | |||||||||
EFF | 350 | 467 | 0% | 0 | |||||||||
1 BR | 500 | 667 | 20% | 133 | |||||||||
2 BR | 1,000 | 1,333 | 80% | 1,067 | |||||||||
3 BR | 1,200 | 1,600 | 0% | 0 | |||||||||
4 BR | 1,400 | 1,867 | 0% | 0 | |||||||||
AGGREGATE AVG. DWELLING UNIT AREA | (AGG) = | 1,200 | |||||||||||
GBA sf per parking space | a= | 800 | |||||||||||
Enter zero in the adjacent box unless you wish to override the AGG value calculated above | 0 | ||||||||||||
A dwelling unit mix table is attached to the design specification template of every forecast model. A typical multi-family design specification template for the parking lot design category is illustrated by Table 3, but the dwelling unit mix table has been separated to show the two options noted as Tables 1 and 2. Normally, a dwelling unit mix table is part of a design specification and a complete set of values is used by embedded equations to predict dwelling unit quantity NDU as the number of building floors increase or decrease.
TABLE 3 THE DESIGN SPECIFICATION TEMPLATE of FORECAST MODEL RG1L
Given: | GLA= | 10.000 | 435,600 | SF | ||||
Public/ private right-of-way & paved easements | RDA= | 0.100 | W as fraction of GLA | 43,560 | SF | |||
NLA= | 9.000 | NLA in acres | 392,040 | SF | ||||
Facilities and features to remain as fraction of GLA | UNB= | 0.200 | 87,120 | SF | ||||
X= | 0.300 | fraction of GLA | 130,680 | SF | ||||
Buildable Land Area Remaining | BLA= | 7.000 | acres | 304,920 | SF | |||
Est. gross pkg. lot area per pkg. space in SF | s = | 350 | enter zero if no parking required | |||||
Parking lot spaces planned or required per dwelling unit | u= | 1.5 | enter zero if no parking required | |||||
Garage parking spaces planned or required per dwelling unit | Gn= | 0 | enter zero if no parking required | |||||
Gross building area per garage space | Ga= | 0 | enter zero if no parking required | |||||
No. of loading spaces | l = | 0 | ||||||
Gross area per loading space | b = | 0 | SF | 0 | SF | |||
Project Open Space as fraction of BLA | S= | 0.300 | fraction of BLA | 91,476 | SF | |||
Private Driveways as fraction of BLA | R= | 0.030 | 9,148 | SF | ||||
Misc. Pavement as fraction of BLA | M= | 0.020 | 6,098 | SF | ||||
Loading area as fraction of BLA | L= | 0.000 | 0 | SF | ||||
Total Site Support Areas as a fraction of BLA | Su= | 0.350 | 106,722 | SF | ||||
Core development area as fraction of BLA | C= | 0.650 | C=Su must = 1 | 198,198 | SF | |||
Building efficiency as percentage of GBA | Be= | 0.800 | must have a value >0 entered | |||||
Bldg. support as fraction of GBA | Bu= | 0.200 | Be + Bu must = 1 | |||||
Table 4 compares the results produced by the Table 1 and 2 dwelling unit mix templates when the design specification values in Table 3 are held constant in the forecast model RG1L. The results show that a constant density requirement will not produce consistent results when the dwelling unit MIX and AGG value is not constant. The results become even more inconsistent when other design specification values are modified. In other words, density limits without a complete set of dwelling unit mix and design specification values produce random results.
We annex more land to compensate for random leadership and worry about sprawl because we do not forecast capacity to limit waste and control intensity. Development capacity has been defined with rules of thumb and constrained by ambiguous open space requirements, but it cannot be left to chance if we believe that plans are needed to provide shelter for growing populations within sustainable limits that protect our quality of life.
TABLE 4 COMPARISON of AVG DU AREA (AGG) to DU CAPACITY (NDU)
NOTE: NDU increase declines as floors (f) increase – when all design specifications are constant – because parking lots must expand to serve building area & dwelling unit increases. NDU increases are marginal above 5 stories when all other design specification values remain constant because a building footprint finds it increasingly difficult to shrink in response to an increasing parking lot within core area limits.
PKG LOT SOLUTIONS ABOVE 5 STORIES ENCOURAGE OPEN SPACE SACRIFICE & PKG VARIANCE REQUESTS
T2 | T1 | ||
AGG | AGG | ||
872 | 1,125 | ||
a | a | ||
750 | 654 | ||
e | e | ||
80% | 80% | ||
floors (f) | NDU | NDU | 1-(T2/T1) |
T2 m2e.8 | T1 m1e.8 | ||
1.00 | 120 | 132 | 8.7% |
2.00 | 182 | 195 | 6.6% |
3.00 | 220 | 233 | 5.3% |
4.00 | 246 | 257 | 4.5% |
5.00 | 264 | 275 | 3.8% |
6.00 | 278 | 288 | 3.4% |
7.00 | 289 | 298 | 3.0% |
8.00 | 298 | 306 | 2.7% |
9.00 | 305 | 313 | 2.5% |
10.00 | 311 | 318 | 2.3% |
11.00 | 316 | 323 | 2.1% |
12.00 | 320 | 327 | 1.9% |
13.00 | 324 | 330 | 1.8% |
14.00 | 327 | 333 | 1.7% |
Table 5 indicates that GBA efficiency (e) further destabilizes the results produced by a given density requirement. It shows that the same one story building could yield from 108 to 142 dwelling units depending on its efficiency when the design specifications of Table 3 are again held constant and the dwelling unit mix of Table 1 is considered. This means that parking requirements also expand as efficiency increases -- and open space is sacrificed in response.
TABLE 5 COMPARISON OF BUILDING EFFICIENCY TO NDU CAPACITY
NOTE: NDU increase declines as floors (f) increase – when all design specifications are constant – because parking lots must expand to serve building area & dwelling unit increases. NDU increases are marginal above 5 stories when all other design specification values remain constant because a building footprint finds it increasingly difficult to shrink in response to an increasing parking lot within core area limits.
PKG LOT SOLUTIONS ABOVE 5 STORIES ENCOURAGE OPEN SPACE SACRIFICE & PKG VARIANCE REQUESTS
a | b | c | d | f | g | h | j | k | l |
e | e | e | e | ||||||
60% | 70% | 80% | 90% | ||||||
AGG | AGG | AGG | AGG | ||||||
1,308 | 1,121 | 981 | 872 | ||||||
a | a | a | a | ||||||
872 | 748 | 654 | 581 | ||||||
floors (f) | NDU | NDU | NDU | NDU | |||||
A=1-(b / c) | A=1-(c / f) | B=1-(f / b) | A=1-(f / j) | B=1-(b / j) | |||||
1.00 | 108 | 120 | 10.2% | 132 | 8.5% | 17.8% | 142 | 7.2% | 23.8% |
2.00 | 168 | 183 | 7.9% | 195 | 6.5% | 13.9% | 206 | 5.4% | 18.5% |
3.00 | 206 | 221 | 6.5% | 233 | 5.2% | 11.3% | 243 | 4.3% | 15.1% |
4.00 | 233 | 246 | 5.5% | 257 | 4.4% | 9.6% | 267 | 3.5% | 12.8% |
5.00 | 252 | 265 | 4.8% | 275 | 3.7% | 8.3% | 283 | 3.0% | 11.1% |
6.00 | 267 | 278 | 4.2% | 288 | 3.3% | 7.3% | 296 | 2.6% | 9.8% |
7.00 | 278 | 289 | 3.8% | 298 | 2.9% | 6.6% | 305 | 2.3% | 8.8% |
8.00 | 288 | 298 | 3.4% | 306 | 2.6% | 5.9% | 313 | 2.1% | 7.9% |
9.00 | 296 | 305 | 3.1% | 313 | 2.4% | 5.4% | 319 | 1.9% | 7.2% |
10.00 | 302 | 311 | 2.8% | 318 | 2.2% | 5.0% | 324 | 1.7% | 6.6% |
11.00 | 308 | 316 | 2.6% | 323 | 2.0% | 4.6% | 328 | 1.6% | 6.2% |
12.00 | 313 | 320 | 2.5% | 327 | 1.9% | 4.3% | 332 | 1.5% | 5.7% |
13.00 | 317 | 324 | 2.3% | 330 | 1.8% | 4.0% | 335 | 1.4% | 5.4% |
14.00 | 320 | 328 | 2.2% | 333 | 1.7% | 3.8% | 337 | 1.3% | 5.0% |
T3m1e6 | T3m1e7 | T3m1e8 | T3m1e9 |
I hope Tables 4 and 5 make it clear that independent zoning requirements cannot lead us to the sustainable future we hope to achieve because they are related. This essay shows that one component of a design specification can undercut the intent of another when uncoordinated, and more than one can produce complete confusion. We will not be able to avoid sprawl as long as we attempt to compensate for this arbitrary leadership with annexation.
If you believe that the Built Domain depends on the Natural Domain for survival, then the first step is to define the space required for these natural functions. The space that remains is the only space available for the artificial world of a Built Domain, and it must accommodate the expanding shelter, movement, open space and life support divisions of our built environment. Shelter protects us. Open Space feeds us. Movement and Life Support serve us. Living within the Built Domain will require accurate forecasting of shelter capacity options, since we must avoid sprawl that will consume the face of the planet if unrestrained. Accurate prediction will permit lifestyle options and variety to be evaluated within this domain. Decisions can then be expressed in terms that will lead many toward one goal, since we must protect the survival and quality of life in two separate, unequal worlds.
At the present time the public speaks with emotion in the face of city planning uncertainty. If I substituted the word “medical” for “city planning” in the preceding sentence, I could be speaking of plague in the Middle Ages. We are now faced with a similar challenge in a different time with the same potential consequences. We call the challenge “sprawl” and stare at symptoms, but are not convinced it’s a disease. Some can imagine the problem, but their language and tools cannot reach to the heart of the issue. Emotion becomes a substitute for knowledge and visions provide leadership. It should sound familiar. It’s a path we’ve followed throughout the history we remember.
City planning has reached the “vision” milestone. Within the Built Domain, the next steps require an improved language, a precise measurement system, a standard evaluation format and the ability to duplicate success while encouraging individual personality. This should also sound familiar, since we’ve called these steps the scientific method. In medicine, the goal has been survival with quality based on individual health. In city planning, the goal is survival with quality based on a sustainable relationship between the Built and Natural Domains. If the Built Domain has limits however, we must learn how to shelter growing populations without excessive intensity that threatens quality and survival.
I have no answers, but I have attempted to contribute a language, a specification system, a context evaluation format, measurement standards and forecasting software that can be used to predict options. These are strategic tools. Context research will give us the ability to evaluate their predictions and improve on the random results of the past.
There is no alternative to a policy of life within sustainable limits if survival is the goal. It is just a matter of how the limits will be introduced. Random acts of zoning are not equal to the challenge; but they have established an essential precedent, and represent tactical command potential. It is the policy, plans, tools and information that must advance to improve our strategic potential to construct a Built Domain with a sustainable future.
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