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8/9/2019 Urban Spaces Thermal Conditioning a Comparative Study of Public Outdoor Spaces Passive Thermal Conditioning
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Name: Ismail M Qaznili
Student ID: 4089241
Course: Sustainable Urban Design (K14SUD)
School: School of the Built Environment
Subject: MArch in Urban Design
Number of Words: (1900)
Urban Spaces Thermal Conditioning: A Comparative Study of Public
Outdoor Spaces Passive Thermal Conditioning.
May 2009
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Table of Contents
Introduction............................................................................................................ 1Outdoor Thermal Conditioning .......................................................................... 2The Concept .......................................................................................................... 2The Human Thermal Comfort............................................................................. 3The Methodology.................................................................................................. 4
Thermal Conditioning Case Study.................................................................... 5Matsudo Station Square ................................................................................... 6Matsudo Central Park ....................................................................................... 6Empirical Research Method............................................................................. 7The Results .......................................................................................................... 9
Conclusion .............................................................................................................. 12
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Table of Figures
Figure 1 Study Areas Location Map 8
Figure 2 - 3 Matsudo Square Platform and Street 9
Figure 4 5 Matsudo Park Walkway and Lawn 9
Figure 6 - 7 Right: Matsudo Square, Left: Matsudo Park 11
Figure 8 Distribution Frequency in both areas 13
Figure 9 Attendance total within time interval 13
Figure 10 Attendees correlated to PET Left: Matsudo Square, right: Matsudo Park 14
List of Tables
Table 1 Measuring Instruments 11
Table 2 PET Value Breakdown 12
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Introduction
The rapid change of global climate conditions increases the
consumption of energy and generates large amounts of pollution. The
effect of global warming, the increase of earths temperature forces
the inhabitants of urban areas to rely heavily on artificial air
condition methods which generate large amounts of Co2 emissions due to
the large energy consumption. There for that gives credit in promoting
global warming.
The awareness of this phenomenon has led responsible bodies
concerned with developing urban area to adopt methods to reduce the
effect of global warning causes. Architects are using different design
concepts to reduce reliance on artificial thermal conditioning methods
and promote passive systems.
In the process concerned with achieving passive thermal
conditioning, the focus was mainly on indoor closed spaces, neglecting
the outdoor open areas, but not until recently. Examples of increasing
focus by designers and developers on the outdoor space can be seen in
Bara Funda in Sao Paulo, Tokyo in Japan, Syracuse in New York, and
last but not least Hermosillo in Mexico.
The Aim of this paper is to examine the basics of outdoor
thermal conditioning in design literature, and then will look into two
case studies exhibiting the main points which had been took into
account for designing outdoor thermal conditioning in these areas, and
then will conclude with how effective are these interventions.
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Outdoor Thermal Conditioning
The Concept
Creating an acceptable thermal condition within a given space is
based on objective and subjective variables. They work in interact
together differently based on the place location and the nature of the
users.
Subjective variables are those elements that are defined by the
peoples behaviour based in their cultural and social characteristics
such as the acceptance level of temperature and wind speed within a
time interval or an area.
Objective variables are those elements that are set by the
physical attributes of the all the components that create spaces,
outdoor spaces in this case, such as materials colours and textures,
shapes and formations of masses, the function of the space, and last
but not least and most importantly static and dynamic features of
microclimate.
Ochoa and Marincic (2005) argued that the thermal comfort and
the energy impact on masses are neglected by designers. They suggested
that designers should attempt to address the last two points in and
work toward solving its issues.
Their suggesting is attributed to the following points of views
that;
1. Designers should acquire knowledge pertaining to a
series of fields as diverse than climatology, botany and
geography; however, this knowledge is not always expressed in a
language that they can adequately apply in their work.,
2. Since exterior spaces are normally not artificially
cooled or heated, there is no extra energy consumption directly
related with the outdoor thermal comfort. So developers of
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design tools and software have centred their efforts in thermal
design and efficient use of energy in building indoors,
banishing the landscape microclimatic design., and
3. Furthermore there is a lack of standards and
regulations for outdoors
Herrington and Vittum (1977) in their study of Syracuse in New
York had sought to set the variable related to human comfort in spaces
based on microclimate features within central urban areas.
They focused on the thermal exchange between the users of space
and their surroundings, by taking into account the physical attributes
of the materials and the physiological performance of the human body
in relation to heat transfer and exchange.
The Human Thermal Comfort
The status of the body which ensures the effectiveness of all
the internal functions after exposure to outdoor spaces temperature is
consider a thermal comfort area. This perception of this status is
completely subjective to the users state of mind and physical
condition. The different situations of the users scale the level of
comfort.
Herrington and Vittum (1977) have stated that Thermal stress is
created when the net loss of thermal energy from the subject's body
does not equal the production of heat by metabolism within the body
this mismatch depending on the outdoor temperature will cause either a
drop or increase in the internal temperature of the body. The body
respond to this in the form of skin respiration.
For idle stationed entities, the sensation of comfort results
from stabilising the body internal temperature to 98.6F (Herrington
and Vittum, 1977). Any excessive alteration to the surrounding
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temperature or the inner temperature may cause skin respiration which
is a thermal discomfort.
As for active moving entities, the level of comfort is based on
the body and surrounding air temperature for as long the exchange rate
between the body temperature and the surrounding air is at minimum.
Discomfort occurs in the case of excessive sweating (Herrington and
Vittum, 1977).
The Methodology
Basically to prepare a study regarding outdoor thermal
conditioning, it is important to note that it is based on empirical
research.
These should be carried out in designated times, the time which
considered vital to outdoor activity promotion.
Information is gathered from users subjects directly involved
within the designated area either by interviews or observation,
information such as the personal behaviour in the area, the users
physical characteristics of clothing, sex, age and their motives.
Microclimate information and pattern of air temperature, globe
temperature, surface temperature, relative humidity, wind speed,
incoming short wave radiation, and incoming long wave radiation should
be calculated and correlated with users behaviour in order to
establish a link to help understand what is needed to be done to
promote usage.
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Thermal Conditioning Case Study
Two case studies will be examined to demonstrate the how the
previously mentioned methodology had been implied and it was useful in
measuring and enhancing outdoor thermal conditioning.
The locations are in the city of Matsudo, Chiba prefecture,
Japan. The main characteristics of the area microclimate are a
temperate climate, warm and humid summers, and dry and relative mild
winter seasons (Thorsson, Honjo, Lindberg, Eliasson, and Lim, 2005).
The areas are Matsudo Central Park and Matsudo Station Square in
Matsudo central area.
Figure 2 Study Areas Location Map
(Thorsson, Honjo, Lindberg, Eliasson, and Lim, 2005)
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Matsudo Station Square
A one level elevated two squares next to Matsudo train station,
of an area of 50m by 40m paved with light coloured clinkers. It acts
as a point of gathering in the area of Central Matsudo. Its elevated
platform creates a pedestrians friendly area that connects the station
with the surrounding buildings.
Figure 2-3 Matsudo Square Platform and Street
(Thorssonet et al, 2005).
Matsudo Central Park
An open space area of 2.1 ha with two tennis courts and a
swimming pool, penetrated by walkways. A typical Japanese park located
east of Matsudo Station.
Figure 4 5 Matsudo Park Walkway and Lawn
(Thorssonet et al, 2005).
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Empirical Research Method
The two researches were carried out simultaneously in the park
and the square, within the dates of March 12th till March 24th 2004
between 11.00 am and 3.00 pm. The process was consisting of structured
interviews, outdoor activity observations, and micrometeorological
measurements of both areas (Thorssonet et al, 2005).
For the structured interviews, it was carried out in Japanese
language a single interview lasted for an average period of 30 min,
addressing general information about the subjects such as: age,
clothing, visiting purpose, and desired times. Also it covered a
qualitative assessment of the areas by the subjects.
As for the outdoor activity observation, it was carried out
every 30 min, roughly 11 times per day. The areas were subdivided into
smaller sub areas to ease the observation process.
The data collected were about attendee number, sitting and
standing attendee in the sun and shade, and lastly personal behaviour
such as eating, reading, playing, smoking, and other actions. Also
passers through the site were taken into consideration.
Regarding the micrometeorological measurements, it was
calculated using two stations. Air temperature (Ta), globe temperature
(Tg), surface temperature (Ts), relative humidity (RH), wind speed (W),
incoming short wave radiation (S), and incoming long wave radiation
(L) values were calculated in the most vital parts of the two areas,
using their respective tools as shown in Table 1.
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Table 1 Measuring Instruments
Two fish eye shots were taken to create SVF analysis, one for
each area, with a measurement height of 1.1m (Thorssonet et al, 2005).
Figure 6-7 Right: Matsudo Square, Left: Matsudo Park
(Thorssonet et al, 2005).
Matsudo Square scored 0.61 while Matsudo Park scored 0.58 due to the
vegetation layer presence (Thorssonet et al, 2005).
Wind speed was calculated at 2m height then it has been scaled
down using Sverdrups power law. Surface thermometers were used to
calculate surface temperature every 30 min (Thorssonet et al, 2005).
In attempt to investigate the thermal conditioning of the both
areas, air temperature (Ta), the mean radiant temperature (Tmrt), and
the physiological equivalent temperature (PET) values we correlated
altogether.
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By using computer calculation using the RayMan application,
which calculates (Tmrt) and (PET) based on urban areas parameters such
as (Ta) and humidity, time interval, and the Aledo of the nearby
surfaces.
The indicator used to express the PET value is explained in the
following table:
Table 2 PET Value Breakdown
The Results
The total number of respondents is 469, 219 at the park and 250
at the square. 74% were at the age between 21-65 years. 49.6% were
female and 50.4% were male.
Thermal Sensation
The distribution frequency of the thermal sensation resulting
from the carried interviews in the square shows that 25% of
respondents found it comfortable, 20% of respondents found it warm,
and 15% found it cold. (Thorssonet et al, 2005).
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Figure 8 Distribution Frequency in both areas
While the distribution frequency resulting from the interviews
carried in the park shows that, 30% of the respondents found it
comfortable, 15% of the respondent found it warm, and 20% of the
respondents found it cold. (Thorssonet et al, 2005).
Outdoor space Usage
Figure 9 Attendance total within time interval
Attendees of Matsudo Station were exceeding those of Matsudo
Park; an attendance peak could be noticed at 12.30 in Matsudo Park and
an attendance peak at 13.5 in Matsudo Square.
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Figure 10 Attendees correlated to PET
Left: Matsudo Square, right: Matsudo Park
By correlating the two outputs, PET frequency and the number of
attendees, we find that the number of attendees is not affected by the
PET conditions in the square case due to the fact that people dont
spend much time cause it is functioning as a joining hub between the
station and the surrounding areas and the users dont worry so much
about being discomforted.
On the contrary, the number of attendees on the park is
dramatically corresponds to the PET since the park is functioning as a
resting place and the duration of staying is more greater than that of
the square, people are becoming more subjective towards the PET
conditions.
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Conclusion
To conclude, the people behaviour, the place function, and the
climate characteristics dramatically affect the thermal conditioning
perception of the users.
The empirical method used to measure the performance of outdoor
open spaces is still traditional, but still it gives a clear and
comprehensive image that help in evaluating the efficiency of outdoor
spaces.
Outdoor spaces thermal conditioning is matter which is more
subjective rather than objective.
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References
HERRINGTON, L. P. and VITTUM, J. S. Human Thermal Comfort in Urban OutdoorSpaces, 1977
Thorsson, S., Honjo T. Lindberg, F. Eliasson, I. Lim, E. Thermal comfort conditions andpatterns of behaviour in outdoor urban spaces in Tokyo, Japan, 2005
Ochoa, J.M.I. and Marincic, I. Thermal comfort in urban spaces: The case of very warmand dry climate2005