Population Density & Factors effecting it

Increasing population has created a dire need of housing more and more population within the limited space, especially in cities, as a result population density is increasing and high rise buildings are constructed, the extent it can accommodate population is discussed here.

Population Density

 

Purpose of study

To calculate population density as it is essential before executing a project such as housing. In current scenario of increasing population high rise construction is preferred because of notion that increase in number of floor is proportionate to increased capacity and to find out upto what extent it is true.
To find whether a said construction is possible or not considering various parameters like population density, minimum space requirement, spatial standards and affordability. It also helps in establishing relationship between spatial standards and population density along with understanding factors which effect population density.

Definitions, Formulas & Examples

1. Population density– Population density is the number of people per unit of area, usually hectare or square kilometer. Population Density is of various types and is calculated as per requirement. Examples include Town/Overall Density, Gross Residential Density (GRD), and Net Residential Density.

i)  Town/Overall Density – It is calculated for a whole town or city. Generally used for predicting the population growth, finding population growth trend and forecasting.

Town/Overall Density =                         Total Population/Total Land use Area (Residential)

ii) Gross Residential Density (GRD) – It is the number of housing units divided by gross residential area .Gross residential area includes all facilities upto neighborhood level like parks, collector road and school, school. GRD is generally expressed in units per hectare.

Gross Residential Density =                Total Population/Gross Residential Area

iii)   Net Residential Density (NRD) – It is a measure of housing density expressed as dwelling units per hectare. The net residential area includes only residential plot area (including access roads & incidental open spaces) and can be calculated as follows:

Net Residential Density =               Number of dwellings/Net Residential Area

2. Floor Area Ratio (FAR) – FAR is the ratio of total net floor area of a building to the total lot area. FAR describes the intensity of the use on a site.

Factors affecting population density

  • Economics and social factors – Area with high development are more densely populated as compared to areas of low economic growth.
  • Climate, landform, culture – High & compact development is found in hot areas as shadow is preferred whereas in humid climate open spaces are preferred for proper ventilation.
  • Spatial Standards – Spatial standards may promote or discourage population density and differs from place to place.
  • Connectivity/location & accessibility – Areas with better connectivity and accessibility are densely populated.
  • Demographic factors – Mortality, migration effects population density differently and are dependent on other factors like social, geographic and economic factors.

Parameters Studied

  1. Land Cost (per hectare) – (i) Rs.1000/-  (ii) Rs.10000/- (iii) Rs.100000/-
  2. Construction cost (lacs per hectare) – (i) Rs.2500 (1st Floor) (ii) Rs.2250 (2nd Floor) (iii) Rs.3750 (4th Floor) ( (iv) Rs.6250 (8th Floor) (v) Rs.7500 (16th Floor)
  3. Spatial Standards
    1. FAR – (i) 0.6 (ii) 0.9 (iii) 1.3 (iv) 1.6 (v) 1.8
    2. Number of floors – (i) 1 (ii) 2 (iii) 4 (iv) 8 (v) 16
    3. Minimum Space Requirement (per capita) – (i) Floor Space – 25s.q.m (ii) Facility Space – 10s.q.m
    4. Plot Size – 1 hectare
    5. Affordability – (i) Rs.60 lacs (ii) Rs.40 lacs (iii) Rs.20 lacs
    6. Dwelling unit size – 4 Person

Cost & Spatial Standards and their effect on population density

Land cost, construction cost affects population density in varied manner and their affect is in relation with spatial standards like Floor Area Ratio (FAR), per capita space requirement, per capita circulation and facility space.

Table showing possible Net Residential Density

net-residential-density

*considering per capita space requirement to be 25 sqm and facility space to be 10sqm

It is clear from above table that population density does not increase proportionately with number of floors thus high rise construction, it is beneficial to construct high-rise only upto certain number of floors and therefore it cannot be considered as solution for increasing population.

 

Table showing possible density on basis of Land cost, Construction Cost, Spatial Standards & Affordability

 population-density-table-1

*Density considering minimum space requirement for 1 person to be 25sq.m of floor space, 10sq.m of facility space, and 1500sq.m of circulation space for 1 ha of plot.

 

Table showing most feasible construction on basis of Number of Floors & Land cost

 population-density-table-2

 

 

Interpretation & Inferences

1. High rise buildings are seen in area with high land cost as they are economically viable
otherwise project cost cannot be recovered.
2. Buildings upto 2-3 floors are preferred in area with low and moderate land cost as increase in
construction cost is more significant than land   cost.
3. As seen in case of area with high land value, construction cost per sqm is cheaper for even
16 floor then construction cost of ground floor alone.
4. In area with low land cost increase in number of floor from 8 to 16 is more preferable then from 4 to 8 floors
when construction cost per sqm is considered.

 

population-density-graph

Interpretation & Inferences

1. Houses at place of high land cost can only be afforded by high income group else
project cost cannot be recovered.
2. Increasing the number of floor can help in providing house to some extent, in this case
development upto 2 floors is most suitable.
3. High rise construction of 12-16 floors can only be afforded by High income group.
4. Development upto 4 floors are most feasible as further increase in floors significantly effects
construction cost.
5. After a certain limit, increase in number of floors is not followed by proportional increase in density.

 

Conclusion

Constructing 2 floors for lower land cost and 4 floors for a higher land cost is more feasible then constructing only 1 floor, thus high rise construction is preferred in area of high land cost to keep houses affordable and still in some cases only high income group people can afford house in those areas.

Increase in number of floors does not mean a proportionate increase in population density so they are not always a solution to accommodate increasing population.

With an increase in net residential density more space is required on land for purpose like recreation, schools, hospitals etc. which reduces the usefulness of high rise construction.