THE SITE (2)

단지계획 5강 THE SITE (2)

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PRESENTATION ORDER

1. The Site

• Site Identity & change

• Ecology

• Behavior 2. Subsurface

• Soil

• Engineering class of soil

• Soil as plant medium

• Soil Survey

• Water table

• Subsurface problems 3. Surface

• Landforms

• Plant cover

• Site character

• Maps

• Record of survey

• Aerial photographs

• Site reconnaissance

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4. Over ground

• Climate

• Bodily comfort

• Albedo

• Conduction

• Convection

• Specific heat

• Slope and climate

• Shading

• Topography and air movement

• Windbreaks and wind tunnels

• City climate

• Building orientation

• Noise

• Noise attenuation 5. Site analysis

• Systematic surveys

• Synthesis

• Site selection

• Best use

• Performance and relevance of data

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Over Ground

Climate

• The ocean of air, varying temperature, humidity, purity, light, and sound … we prefer certain ranges and rhythms of these things

• We defend ourselves by physiological adaptation and with clothing and shelter

• Climate data on temperature, humidity, precipitation, cloudiness, wind speed, wind direction, and sun path

• Averages are not suffice. Normal maximums and minimums are therefore used

4 Body comfort

• Effective temperature is the sensation produced by the combination of radiation, ambient temperature, relative humidity, and air movement

• Outdoor cold vs. Outdoor heat (Body Temperature 4℃↑ ?)

• The maximum outdoor temperature  65℃ completely dry

& 32℃ completely humid

• Tolerably comfortable … 18 ~ 26℃ (humidity 20~50%)

• Sensation … affected by previous experience, by cultural background, by age, and by the degree of activity

(E.g. “Ideal” indoor temperature; Hypothermia risk for elderly people)

Over Ground

5 Body comfort

• A designer working in a new region should look at the way in which local people deal with their weather.

Traditional buildings and their siting represent accumulated experience.

• The designer is particularly interested in the

microclimate … by topography, cover, ground surface, and structural form … people are in contact … designer can

actually modify … change within distances of a few

meters … confined to … no more than a few stories high

Over Ground

6 Body comfort

Over Ground

7 Albedo

• Heat is exchanged by radiation, conduction and convection

• Albedo is a surface characteristic … fraction of the total radiant energy of a given wavelength incident on a surface that is reflected back

• Albedo of 1.0  perfect mirror

• Relative permeability

• 0.9 for fresh snow, 0.4~0.5 for bare dry sand, 0.2~0.3 for dry clay soil, 0.1~0.2 fro meadows and fields, 0.1 for forests ... 0.05 for black asphalt

Over Ground

8 Conduction

• The speed with which heat or sound passes through a given material, once having penetrated its surface

• Conductivity of natural materials decreases as they are drier and less dense

• Wet sand>ice>concrete>asphalt>still water> dry sand or clay > wet peat > fresh snow > still air (1 to 100)

Over Ground

9 Convection 대류

• Heat and sound are also distributed by fluid movement or convection …

• Speed and turbulence

• Air turbulence increase with height and then decrease again at upper levels

• Wind speed increases with height  Lie down!

• Cooling effects by speed

 a 50 km per hour wind at 0℃ = 6 times the cooling effect of still wind at -12℃

Over Ground

10 Specific heat 비열

• The ability of an object to store the heat it receives (mass*specific heat)

• A house with thick masonry walls will be cooler in the heat of the day, and warmer at night

• Large water bodies with their high specific heat act like climate flywheels

Over Ground

11 Specific heat 비열

Over Ground

12 Shading

• Plants and structures blocking the direct sun radiation

• Deciduous trees are ideal

• Louvers and overhangs

• The path of the sun varies with hours, date, and latitude

• Proportion overhangs and design different façade orientations or window sizes

• Simulation

Over Ground

13 Shading

Over Ground

14 Topography and air movement

• Topography affects climate by its influence on air movement

• Wind speed on a crest vs. on flat ground on the lee side vs. weather side

• Cold air flood … frost pocket

• The shores of seas or large lakes … afternoon and night breeze

Over Ground

15 Windbreaks and Wind Tunnels

• Topographic effects are modified by structures and and plant over

• Structures block and divert winds, or channel them at increased speed through narrow openings

• Tall, thin, long wall is the most effective windbreak

… even more effective if it is not impenetrable (air pressure)

• Air movements between a group of buildings are so complex … therefore it is useful to study air movement on the site by means of a scale model

Over Ground

16 Windbreaks and Wind Tunnels

Over Ground

• Computer simulation

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• Wind speeds affect human beings

Over Ground

Windbreaks and wind tunnels

18 City climate

• Man has changed the microclimate over much of the earth … drainage, clearance, plowing, planting … paving, dense structures, and emission of heat, noise and impurities

• “heat island” … rainfall increases, clouds and haze reduce the sunshine … but reversible … London case

• Extensive city paving … rapid runoff … loss of local humidity and cooling, depletion of groundwater … flood

Over Ground

19 City climate

• Cities are warmer, dustier, drier, more rain, cloud, fog, noise, air pollution, less sunlight

• These defects are not due to the crowding of people but to the nature of city structure, their mechanical emissions, and the substances we choose to consume

• Sources to evaluate the microclimate of a locality

 Weathering of older buildings, knowledge of old residents, appearance of existing plants

• The avoidance of unwanted heat loss or gain, and the positive use of sun energy for heating and cooling … become compelling principles of site design

Over Ground

20 Building orientation

• In temperate latitudes, favorable orientation … south or southeast

 window openings are reduced on the northern and western facades … to retard the flow of heat

 Houses will be placed along access roads running east to west or east-northeast to west-southwest

• Each climatic region, each way of life, each site, has its own requirements

• Contexts and technology …Energy conservation should not be the dominant objective

Over Ground

21 Noise

• The usual problem is to reduce either the level, pitch, or information content of the noise

• Levels measured in decibels (dB)

 scale from 0 to 140

 Each interval of 10 decibels  twice louder than before

 Below 55dB in any outdoor area; 40dB indoors; 35dB in rooms devoted to study or to sleep

• Hi-pitched noises … sudden noises … human voice

• Site survey of existing noise is useful whenever the issue is controversial.

Over Ground

22 Noise attenuation

• Sheer distance: each doubling of the distance  sound level drops by 6dB

• Turbulence, gusty winds, barriers

• Belts of trees are scarcely useful … only for Hi-pitch noise

• Disconnecting sound and sight

• A higher wall close to the source

• Use of nonreflecting textures

• The play of water, the rustle of leaves, or “white noise”

• Site acoustics has focused on the suppression of unwanted sound (↔ architectural acoustics)

Over Ground

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Site Analysis

Site analysis

• Separates transitory of fading features from permanent or emergent ones

• It is advisable to study a site in several ways 1. Search aimlessly

2. Look to the history of the site: its natural evolution, its former use and association

3. Look at the place as an ongoing ecological system, including present human use

24 Systematic surveys

• At this point, a more systematic and detailed survey can be undertaken

• Topographic map, climate data, mapping of activity & circulation

• Temptation to gather too much  information is expensive to gather and expensive to use

• Some standard data require substantial time to prepare (complete and accurate base map)

Site Analysis

25 Synthesis

• Put the survey information into concise and usable form

• Major constraints, problems, potentialities

• The concept of the site will be modified as the design unfolds, as further information is stumbled upon, or must be sought out: site analysis is not self-contained

• The plan develops from the creative effort of the designer

… but must respond to the site

Site Analysis

26 Site selection

1. Reducing possible sites to a manageable set of

alternatives by a simple screening based on judgments of thresholds

2. Personal reconnaissance to eliminate unacceptable localities

3. Analysis in depth and comparison of preliminary layouts

Site Analysis

27 Site selection

Site Analysis

28 Best use

• It demands … careful analysis of the place as an ongoing social and ecological system, the context of locality, possible market

• Comparative analyses are made for each set of use and purpose (sketch layouts, market analysis, schedule of probable costs and benefits)

• A choice can be made … using qualitative judgments that balance ecology, market, and social purpose

Site Analysis

29 Permanence and relevance of data

• Site planning must increasingly be seen as a continuous stream of modifications applied to a changing landscape

… Site analysis should be continuing process on which continuing design can be based.

Site Analysis