The concept of FAR developed based on New York City of America to prevent tall buildings from obstructing too much light and air.
• Before 1916, New York grew taller with intense tall buildings obstructing too much light and air and resulting dark ‘canyon’ effects in streets.
• ‘Bulk zoning’ controls began in New York in 1916 which limited the height and required setbacks for new buildings to allow the penetration of sunlight to street level. Its key tool was the building setback, resulting in the famous ‘wedding cake’ skyline of buildings such as the Chrysler Building (1930) and the Empire State building (1931). There was no setback at road side. The law allowed to build a certain height upon setback area and then once reached that height, you had to step back, and build another certain height again. There was a formula for height depended upon the width of the street. The more road width is, the higher the building will be. After reaching 25% of plot area, a skyscraper of any height can be built.
• In the 1920s Architect Raymond Hood generated concept of expansive open spaces – a “modern city of sunlight, air, and free circulation.” Later continued to promote the concept in numerous places in response to the contemporary debate planners over the skyscraper and congestion. He proposed replacing the existing buildings with tall, slender towers surrounded by wider streets. The grid would be replaced by a repeating pattern of two or three towers per block, with fourteen times the amount of street space. Hood’s solution was a proposal to create incentives for developers to build on a smaller percentage of their lots. His new formula proposed a limit on volume based on street frontage: the developer could build a fixed amount higher for each foot that the building was set back from the plot line. This was the origin of the Floor Area Ratio concept.
Building with surrounding huge plaza as open space (right).
• Raymond Hood was a follower of great architect Le Corbusier’s. Le Corbusier’s “towers-in the- park” concepts were influencing planning thinkers, and the concept of incentive zoning—trading additional floor area for public amenities—began to be put forward. The idea was to emulate the perceived success of The Seagram Building designed by Architect Ludwig Mies van der Rohe ; Philip Johnson, with its public plaza.
• At 1949, consultant firm of Harrison, Ballard, and Allen produced first set detail concepts of FAR based zoning, that enacted and took effect in 1961ordinance.
The City of New York offered developers a higher Floor Area Ratio (FAR) in exchange for creating public plazas at new developments so, in theory, as the city built a world-class skyline, it would also create world-class public spaces. The concern was not to increase density but to allow more light and air within the same density. Later, the principles behind the 1961 ordnance were however copied globally.
c. Problems ; Criticisms of FAR based controls
• FAR is a poor predictor of physical form. It should not be used only to conserve and enhance neighborhood character.
• Zoning plot mergers enable developers to assemble small lots into the larger merged plots and build efficient, economical new buildings with less footprint. If FAR is carelessly combined with traditional setbacks, assembled lots have a considerable advantage over individual lots, which has a negative effect on fine-grained cities and the diversity of ownership (https://en.wikipedia.org/, 2018).
• FAR allows and often encourages the ‘stacking’ of mass in one corner or one part of a site to achieve height. This ‘precinct planning’ can disrupt streets lines, reduce enclosure of streets and harm genuine urban character.
• It is difficult simultaneously control bulk and infrastructure demand. Because different land uses have different impacts (such as traffic generation per unit floor area).
• There are provisions for split plots in FAR. “split plots” create confusions and prediction and provide infrastructure and service become too permissive.
• Incentive floor area bonuses for certain purpose and use, very often produced meaningful public benefits.
• Maximum FAR do not always guarantee high density development; there are other factors.
• According to urban economist Bertaud ; Brueckner (2005), too low FAR can result in a suboptimal distribution of density, where inexpensive service make housing less affordable to the poorest, and make urban labor markets less accessible.
• Use of FAR poses especial difficulties on the coast where site boundaries can be expanded considerably through land reclamation (LAINTON, 2011).
d. Misconception about FAR
• If F.A.R is low, we cannot go for high-rise development
• Land value is high and is Sky-rocketing. Hence F.A.R. has to be increased considerably.
• If F.A.R. is increased, prices of Flats will come down.
• Land is precious and scarce; hence F.A.R. has to be increased considerably to house the exploding population.
• If F.A.R. is not increased, the common man cannot afford a decent shelter.
• If F.A.R. values are not increased considerably, major projects like IT Parks will not come in the city.
• Very high F.A.R. can improve the employment opportunities in this sector.
• FAR pressurize for higher building heights that makes buildings more vulnerable to earthquake.
• FAR regulation promotes soft-story for functional and aesthetical purpose.
• Creating air circulation passage/tunnel by increasing set back;
• Creating direct sun light passage on open areas by reducing building footprint.
• Setback will be wider incorporating MGC that enables increased natural ventilation;
• Minimizing the out-of-scale appearance of large homes relative to their lot size and to other homes in a neighborhood;
• Minimizing loss of light and privacy to neighbors caused by the construction of large homes;
• By creating 50% of the open space to be unpaved within each built up area, the development site would allow more rain water to recharge the ground water table.
• the increase of potential urban green spaces contributes to the features of organic waste recycling, climate amelioration in terms of overall temperature reduction and subduing the heat-island effect, hydrology, carbon storage and sequestration, pollution control and biodiversity.
• Bioclimatic design discovers and enhances the natural potential of a site, including solar light and heat, wind, and temperature changes. FAR Maximize the Potential of Bioclimatic Designs.
• There are several benefits to incorporating plants into the building itself. The shade provided by the plants reduces the cooling load of the building and to that extent, also helps to reduce the building’s contribution to the urban heat-island effect.
• Hydrological benefits are also derived. Not only do the plants themselves capture rain, and the soil on which they grow help reduce runoff, the remaining rainwater can be collected for human use within the building. The plants and growing medium help to sieve and filter the water so that less of the rain needs to be rejected.
• Planted waterbodies can also be designed to help recycle wastewater for reuse within the building.
• Beyond this, plants in high-rise buildings also help to humanize the building and give tenants a stronger emotional relationship to the ground. If well-tended and healthy, plants and greenery are generally welcomed for aesthetically pleasing effect to most people.
• Generating greenery and healthy spaces for walking inside the plot.
• Injects and recreates social space within plot areas.
• Achieving psychological benefits and wellbeing from open spaces.
• Creating opportunity for privacy and permeability
• FAR creates flexible spaces within a residential plot by a combination of mandatory and voluntary set back.
• Implications for Developers: An increased FAR allows a developer to complete more building projects, which inevitably leads to greater sales, decreased expenditures per project and greater supply to meet demand. Density bonuses grant additional height or “floor area ratio” (FAR) to developers than allowed by the zoning code. Bonus density allows developers to increase floor space on projects, which in turn increase profits.
• Impact on Land Value: The impact that FAR over land value cuts both ways. In some instances, an increased FAR may make a property more valuable. Say for example, an apartment complex can be built that allows for more spacious rentals or more tenants; or a developer who can build a larger apartment complex on one piece of land.
• Far go for uniformly variable road width at different urban areas and helps to Develop dense and Interconnected Networks of Streets. Thus, come ease of traffic movement which also has a positive impact on land values.
f. Integrated architecture, greenery and energy efficient Urban design and its Effect upon a city
FAR Mainly determine the density or intensity of development of an area with minimum footprint of a building. Decrease of hard surface and orderly development provide sustainable integration of (Engineering) and nonstructural (Ecological) mitigation for better performance in urban resilience.
The benefits of FAR at urban scale:
• Reduce urban heat island effect by recreating greeneries on open spaces, balconies, rooftops etc. can bring ecological balance in the city; thus, mitigation of urban heat islands can potentially reduce national energy use by 20% (Akbari et al. 2001).
• Thermal environment of urban spaces plays a great role on the quality of life in a city. It directly affects people’s behavior and usage of outdoor spaces. Plot integrated green area can Lessen cost of artificial air-cooling energy up to five to ten percent (Akbari et al. (2001).
• Vegetation and unpaved ground condition also decrease storm water dynamics, thus helping cities to manage the consequences of heavy rainfall, as in the case of Dhaka city.
• increase in vegetation created by morphological transformation can mitigating local temperature up to 10% (Ong, 2003).
• Increase of permeable land enable to recharge urban ground water table.
• These spaces allow external room for garden, social meeting place and children play area in morphological exercise as a dynamic tool can generates communal activity hosting lots of measurable and immeasurable social benefits.
• Impact on Potential Developments: FAR is a key determining factor for development in any country. A low FAR is a general deterrent to construction. Many industries, largely the real estate industry, seek hikes in FAR to open up space and land resources to developers. FAR Provide directions, development management, and plan corrective steps. Guide progress on chosen direction for sustainability and minimize additional expenditure of future growth. Encourage investment and accommodate demand for development.
• During an urban disaster, appropriate road densities are required in order to properly operate emergency response activities and to provide evacuation routes. FAR fixes ; force for minimum suitable road width that the plot and neighborhood can uphold not only accessible ease of transportation at normal periods but also for safe evacuation of citizens and proper emergency vehicle operations.
• Keep ; maintains Accessible Resident and Job Densities taking social and economic features into consideration.
• Adapting designs and layouts of buildings and streets to fit specific local climatic conditions.
• FAR based designed buildings are of different height, shape and size mean different population capacity, economic benefits and traffic pressures. That break monotony ; provide hierarchy at Urban scale.
• Guides architects to Promote Energy Efficient Urban Form design which have a Direct Impact on health ; performance, Infrastructure Costs and Investments.
• The two components—built environment versus planted landscape—compete for site coverage. The general recommendation is to encourage increased greenery and higher levels of tree cover and biodiversity. However, enlightened architects and designers are looking at ways to incorporate greenery into their designs; FAR gives them freedom of choice ; more flexibility.
• FAR can Establish balanced Mixed-use Developments engaging housing buildings, office buildings, shops, and urban amenities reduced the demand for motorized travel, shorten average travel distances both for commuting and personal trips, and promote walking and other non-motorized travel.
• Energy is one of the most important ingredients required to alleviate poverty, realize socio-economic and human development. FAR guided transformation of urban forms are influenced primarily by political economy, transportation technologies, land markets, and urban development policies. FAR guides for flexible Urban Form that Greatly Affects Low Energy Use and emission.
4. Floor Area Ratio (FAR) at Dhaka Metropolitan Imarat Nirman Bidhimala ‘2008
The unique feature of Floor Area Ratio was introduced at 2008 act to manage the growth of the city by providing rules of building coverage area, allowable floor space and relation among building height ? road width and plot size (Shafi, 2010). It was believed the new regulations will be involved in improving the environmental situation of built areas and allow greater scope for passive design approaches aimed towards lowering energy consumption.
Another important focus on providing for the safety of the occupants regarding fire hazards, strictly imposing regulations for the means of escape from a building and for access of fire trucks to all sides of the building on site.
The new act mandates to provide signed ‘as-built’ drawings by architects after construction of any project which was thought to go a long way in stemming unlawful construction.
Building Construction Rules 2008 seek to control development plot-by-plot and case-by-case by development control on setbacks, site coverage, construction of garages, access to plot, provision of lift, land use of that particular plot, and height of building, restricting the height referring to BNBC Rules 1996.
opportunity for architects to maximize liveability by variant Urban form design.
Zaman & Laing (2013) has developed following comparison between previous acts and Building Construction Rules 2008 known as Dhaka Imarat Nirman Bidhimala, 2008.
Building Height: Either FAR or the Civil Aviation Authority restricts building height.
Buildable area: The main principle is that the allowable buildable area is fixed. It is the multiplication of plot area with FAR index that if fixed upon land area & road width.
Density of Built Form, Environmental impacts and Energy Efficiency
One of the biggest changes that this new Act brings about is a change in the density of residential areas. Density has direct impact on the solar radiation exposure as well as thermal condition. Density also impacts the wind flow potential of areas through the presence or absence of obstacles to the regional flow pattern. Excessive ground coverage is also responsible for low water absorption, lowering humidity and raising rain water runoffs.
The amount of free ground area (green into a more usable and defined shape) is considerably increased by the new rule, considerable improvement in terms of the ratio of open: built up space than of previous rules.
Ratio of open area to covered area
Within the limits of the allowable buildable area, different clients will have different preferences – some will require more area per floor, some many opt for more floors and hence apartments for renting or selling and so on. So instead of the past monotonous development pattern, the new regulations allow and encourage variations. (Figure 3).