Passive Design with Natural
Light and Air: Crucial Component of Change in the Cityscape
By: Ar. Jorge M. Mission
Ph.D. UAP
(This article is written as
an advocacy of UAP Mt Kanla-on Chapter (UAPMK) on its GREEN EARTH BLUE SKY
agenda on environment and a contribution to the celebration of the 2012 World
Day of Architecture with the theme “Architects are City Changers”. UAPMK is
also assisting the Department of Energy –Visayas Field Office in disseminating
the Guidelines on Energy Conserving Design of Buildings through its Information
, Education ,and Communication Campaign (IECC) in implementing the country’s
Energy Reform Agenda.)
Primary Points
Climate change has been an
issue affecting human all over the globe today. It affects all spheres of human
life –social , economic , political , cultural , and other personal human
activities . Evident enough in the climate patterns , unstable temperature and
its threat to human comfort , trigger challenges on creative ways for possible
recovery of the lost resources of the earth in order to restore a greener earth
and a bluer sky. Alternative approaches for a clean energy , reduction of
carbon emission, new technology on renewable energy ,and the like ,continuously
evolve. Information, education, and communication campaign has always become a
program of private and government institutions.
Architectural edifices in the
Philippines are not excluded from the phenomena. On – going challenges in building
designs confront architects , and allied professionals to design buildings that
are considered “green”. Creative approaches are openly called for effective
design models. Energy efficiency and conservation in building designs are also
the current focus and priority for a more functional facility and with the use
of sustainable resources. Hence , building components are affected by the
disastrous effects of climate change , - structural framings and foundation has
to consider earthquakes; roofing and wall materials needs to resist heat ;
openings and other innovative designs shall be provided with air and light
ventilation and; and
vegetations or shrubberies for
landscape entourage can be effective means for carbon sequestration or give its
share in the carbon sink.
Eventually, these primary
points will contribute in the change of cityscapes on Philippine architecture
when building designs shall exploit obtainable and existing potential sources
of energy .The use of natural light and air ventilation is significant enough
to influence an impact in the conservation of energy. In addition, benefits of
natural ventilation are numerous enough – from low maintenance and consumable
cost, less hygiene problems, and psychological benefit of connectedness to nature.
Architects , engineers and allied professionals are duty-bound to put into
effect climate-adaptive designs and building technologies that will benefit
clients , the community and stakeholders of the profession.
One of the concerns in
celebrating the WDA is that, “Architects will play a crucial role in evolution
by their capacity to meet the challenges of global urban sustainability and
develop the tools needed to create resilient and sustainably liveable cities.”
Further it is moving towards
“mitigating
climate change, reducing polluting emissions, and better management of
resources and energy.” Further , it aims for the structuring of cities ,to be
socially inclusive , accessible and equitable , eliminating discrimination and
precarious housing ; developing cities that can resist crises and cataclysms,
whether natural or induced by man ; developing economic, educational and
creative opportunities for all; and ensuring the security and sanitary
conditions vital to all individuals. The following are noteworthy information,
principles and concepts highlighting some salient provisions from the DOE Guidelines
on Conservation on Building Designs (DOE-GECDB). Understanding these
matters could help architects address issues confronting climate change by
putting into concrete practice Passive Control approach as they integrate them
in the design of buildings and other related architectural projects.
The Philippine Climate
According to Philippine
Atmospheric, Geophysical and Astronomical Services Administration (PAGASA),
Philippines have a Tropical Rainforest Climate with two (2) seasons – wet and
dry. Dry season starts mid- November and ends up to mid of May. Cool and ocean
breezes start on November up to the end of February. March to May as the
hottest month and followed by a wet season from June to October being hot and
humid. April and May has the hottest temperature from 28°C (83°F) up to 38°C
(100°F) and rainfall varies but a rain year –round in most place of southern
Luzon. An average temperature of 25.5°C (78°F) is during January as the coldest
month.
Pagasa records there are 20 (or
even more ) typhoons or “bagyos” across the country lasting for three (3)
to four (4) days. Normally after downpours of heavy rain during nights and
early mornings, steamy and sunny days follow on wet season.
There are 4 types of seasons:
Type I-Two pronounced seasons: dry from November to April, wet during the rest
of the year; Type II-No dry season with very pronounced rainfall from November
to January. ; Type III-Seasons are not very pronounced; relatively dry from
November to April and wet during the rest of the year. ; Type IV-Rainfall is
more or less evenly distributed through the year.
The Thermal Human and Visual
Comfort
The climatic condition of the
country is much affecting the built-environment of any region. Due to this,
thermal human comfort and good lighting or proper Illumination from natural
light source in non-air conditioned buildings and spaces are called for in
order to produce energy conserving architectural designs , appropriate
engineering , and aesthetically sound buildings of any type –residential,
commercial, religious, public and private institutions, and the like. Thermal
human comfort is directly affected with solar heat , and in fact to some extent
will affect indoor air quality (IAQ). Good natural light ventilation could
serve good and healthy visual comfort to the user, however be noted that only
with effective means of control or devices shall be provided in order to retain
acceptable temperature and evade the increase of solar heat gain to create
thermal discomfort.
The
DOE-GECDB gives the general principles of thermal comfort. It enumerates the
main variables that affect human comfort as to the following: dry bulb
temperature; relative humidity or wet bulb temperature; air movement;
ventilation; and thermal radiation from hot surface (ceiling, walls, and glass
window). It also includes indoor air quality.These variables are
significant inputs to consider in the building design process.
1. Dry bulb temperature, usually referred as “air temperature”, is one
consideration in a building that is affecting the interior environment. Air
temperature affects human comfort. When heat discomfort occurs , cooling is
necessary. This means that the use of power or motor gadgets, equipments or
appliances will depend on the heat gain accumulated within the room or space
that requires high cooling requirement in hot environment. Therefore, the lower
the air temperature, the less necessary in the use of these energy consuming
equipments in order to cool the place. In an actual experiment in the locality
of Bacolod City, outdoor dry bulb temperature marks 42°C at 1:00 pm , and for
indoor bulb temperature is 33°C at 2:30 pm . An early morning indoor
temperature at 6:00 am could get 27°C so far. If an indoor temperature could
only be maintained at average of 27°C for the rest of daytime, possibly
electric bill will become lower and shall be meaningful.
2.Relative Humidity or
wet-bulb temperature , an indication
of the amount of moisture in the air, is another factor to look into in
achieving thermal comfort. The recommended humidity level to achieve the most
comfortable environment is 40% –50 % , nevertheless, a range from 30% to 60%
will also be acceptable . However ,in comparison to the DOE-GECDB , the 60%
relative humidity is already the maximum for air conditioned buildings where
50% shall serve as the minimum.
3.Air movement adds another function in achieving thermal comfort in
the design of building at the same time to cause energy conservation. Building
orientation on the windward side where the source of wind comes from , shall be
the basis of site planning. Leeward , the opposite side of the windward , is
understood as a better position where the building could release hot air. Air
movement in warm or humid conditions can cause heat loss without any change in
air temperature.
Effective entry or inlets (infiltration
for air leakage) of air could be achieved when openings of the structure
are well oriented to the windward side as it gets positive wind pressure. Exit
or outlets (exfiltration for air leakage) of air will always be
effective when openings are also provided on the leeward side as it generates
negative wind pressure. Air movement significantly contributes to air
circulation inside the building in terms of air change depending on the type of
buildings. Usually air change depends on , coefficient of discharge (Ce or
effectiveness of opening , 0.5 -0.6 for perpendicular wind ,and 0.25 -0.30 for
diagonal wind ), area of opening ,and wind velocity. Generally , a space may
need (four) 4 air change per hour.
4.Ventilation -Natural light
and air : Thermal comfort will always be the consideration
especially in hot and humid country like Philippines. For energy conserving
designs, natural ventilation could help ease the warm environment with
sufficient supply of air. “In order to breathe air, a human
being needs 21 % of oxygen.” When a ventilation rate drops below the level of
16.5 %, a person will lose consciousness. Interior space must be very well
ventilated not only in terms air but also with light.
The DOE guideline states that “as a general rule,
ventilation rate of 2.8 m3/min to 5.7 m3/min per person is adequate in practice if the average
indoor air temperature rise of not more than 14 ºC is to be maintained as a
result of body heat. Where power-driven and other heat sources are present, a
higher ventilation rate is necessary.”
Further DOE-GECGB address the
aspect on –Natural Ventilation by Window Opening:” The influence on the size
of windows on the internal air movement depends to a great extent on whether a
room is cross-ventilated. If a window is located on one wall of a room,
its size has a little effect on the internal air velocity. However, an even
distribution of windows, and the correct choices of sashes, will help to
improve the ventilation even the windows are located in one wall.
Two natural air ventilation
types of method could be integrated in the design process, -the stack effect,
and the wind-induced method. Stack effect may only be effective when
openings are available at higher heights where hot air inside the room can be
released. Due to buoyancy effect hot air rises up because it is less
dense than cool air.
Effectivity of cross
ventilation happens when two walls are provided with openings. Even by
experience, extent of its effectivity however is also affected by orientation
of the building to avail prevailing winds, the shape of the structure,
uninterrupted airflow from outside, and to a lesser extent, the arrangement of
rooms and the position of interior partitions. No how matter a room could be
well ventilated, it has to be noted that Heat Index, the human-perceived
equivalent temperature, could still effect. Possibly, when the temperature
is 90 °F (32 °C) with very high humidity, the heat index can be about 105 °F
(41 °C).
Provisions for natural
ventilation and lighting in the DOE-GECDB states that, “in natural
regulations, it is specified that every building shall be provided with: natural
lighting by means of windows, skylights, fan-lights, doors, and other
approved natural light transmitting media; and natural ventilation by
means of windows, skylights, fanlights, doors, louvers or similar ventilation
openings.”
5. Thermal radiation and the
Overall Thermal Transfer Value: Heat
gain inside the building is always brought by thermal radiation or heat
conduction received by the building envelope such as opaque external walls,
glass windows, opaque roof, and skylight. An architect and his allied
professionals, must have sufficient data of materials and their characteristics
, mechanical or chemical properties , in order to know what materials to
specify whether it could contribute or avoid heat gain by conduction of
building component in terms of “U” value (a measure of how much heat will pass
through a thermal object), or “R” value, (resistance
to heat flow). The guidelines specify that, in the case of a
non-air-conditioned building, any external wall abutting a habitable room shall
have U-value of not more than 3.5 W/m2ºK.
The
Overall Thermal Transfer Value (OTTV) of the building envelope determines the
quality of the building whether it is energy conserving or energy efficient.
Although the OTTV is normally used for air--conditioned buildings, it would be
a guiding principle in the architectural design process to consider natural
ventilation.
DOE-GECDB elaborates that OTTV
concept means, “the solar heat gain through building envelope constitutes a
substantial share of heat load in a building, which will have to be eventually
absorbed by the air-conditioning system at the expense of energy input. To
minimize solar heat gain into a building is therefore the first and foremost
consideration in the design of energy efficient building. The architectural
techniques used to achieve such purpose are too numerous to mention. Siting and
orientation of a rectangular building to avoid exposure of its long facades to face
east and west, for instance, is a simple means of reducing solar heat gain if
the building sites permits. Appropriate choice of building shape to minimize
building envelope area and selection of light colors for wall finish to reflect
solar radiation are other common sense design alternatives to lower solar heat
input.”
6. Indoor Air Quality: Passive design with natural air and light contributes
to indoor air quality. Humidity control and ventilation already mentioned
earlier are also affecting indoor air quality. Other aspects are filtration
level, sanitation, and odor. Filtration level concerns with the
level of respirable particle (smoke, dust, etc.) found in the place. Presence
of bacteria, molds, and viruses cause sanitation problems, while unsatisfactory
odors are brought by volatile organic compounds (paints, pesticides, cleaning
liquids) shall be avoided. It will take effective number of air change to
remove these pollutants to maintain a habitable indoor air quality.
Being “Green” and Natural
There are other attributes to
describe what a Green House , a Green Building or any of its components -
eco-friendly; environment friendly; sustainable building; eco–architecture;
green architecture, green engineering , green technology etc...To certain extent,
it can also be attributed to a “natural building” ,although it differs in terms
of technology application. Buildings and houses in order to be labeled as green
and natural, must always give visible effect in terms of energy conservation
and energy efficiency. Green rating systems are established; standards and
labeling for household appliances; energy management; energy audit; and
recognition awards are advocated to promote energy conservation and efficiency.
A new Enercon Law is also expected.
Sufficient definitions were
already established in other venues in understanding what a green building ,a
house or structure is. However, the definition by Engr. Nestor Archival may be
easier to understand that could summarize the information discussed earlier.
Archival, who topped the Pitong Pinoy Awards, describes a GREEN HOUSE as
“the structure and the environs that shelter, protect, and nurture life. It is
the habitat for safe, healthy and happy living. It is a house where one can breathe clean air; a house that is not
too cold and not too warm; a house that is not too humid and too dry; a
house that gets light from the sun during the day; a house that can let air
move in and out as desirable; a house that conserves water and energy; a
house that
was
constructed with mostly local materials, some of which may be reused or
recycled; a house conducive to sustainable living.”
Passive Control Approaches
and Design Possibilities.
There are possible approaches
in order to apply Passive control in buildings and houses. The utilization of
natural resources and potential energies of the locality must be first utilized
in order to avoid or lessen the use of any mechanical means of ventilation, yet
retains comfort benefits to the occupant.
By professional judgement, natural
light and natural air ventilation, and the Overall Thermal Transfer Value
(OTTV) of buildings are closely correlated. They are symbiotic in terms of
thermal comfort at the same time affecting lighting and visual qualities of
space as well. This would mean that every building component as a channel of
solar heat gain causing the generation of overall thermal transfer inside the
building space must be given attention. This would even consider from the very
start of site selection to site planning and development as part of the
building design process.
In site selection,
whether in the urban or rural area , off-site factors and its context are
initial parameters to consider ,like wind direction and pressure , solar
orientation , adjacent buildings , outdoor temperature, flood history , noise
,smell and others are essential in the design process. The location of a
structure will influence much the quality of building design and an advantage
for new projects especially during the pre-design phase. Energy conserving
building design starts from site selection. Retrofitting may only be a solution
for old buildings.Studying the Comprehensive Land Use Plan (CLUP) of a place,
may help in choosing a practical building location while places adapting New
Urbanism or Ebenezer Howard’s Garden Cities of Tomorrow , may
benefit claims of these planning concepts in greening the structure.
In the case for site
development planning, the shape of a building and its exposure to solar
heat shall be given attention. Shorter side exposed to sun is best to avoid
accumulation of heat through solar radiation on walls and windows. In addition,
trees, shrubs, flora and of other type of vegetation that will cover the
building will prevent solar heat from entering the building.
For buildings, external walls,
roof, windows, skylights, are components of building envelop that determines
the Overall Thermal Transfer Value. Generally, using appropriate materials with
effective heat resistance from a direct solar radiation will prevent if not
reduce heat gain. Type of roofing materials, innovative strategies, provisions
of adequate ventilation, insulation, are crucial features of design
adaptations. The use of skylights can always help save energy while harnessing
the power of the sun for lighting the space.
The type of materials and
performance of external walls to serve as thermal mass in absorbing thermal
energy , the method of construction to be used for external walls, a well-
arranged location of openings for air or wind infiltration are a productive
design approaches. Installation of an appropriately -sized windows to allow
natural air for cross ventilation and type of windows specified whether awning;
jalousie; sliding, or maybe louvered, would help direct or redirect the
wind
for proper building ventilation. Sun shading or hot daylight blocking can be
introduced through window canopies , overhangs , outer screen , or trellis . In
addition glass windows can prevent or minimize effects of solar radiation
through glass films or interior blinds. When possible ,sunscreen shall be
provided at the exterior side of windows. Much favourable technique when
interior walls shall be provided with cuts in the lower portion and the same at
the higher portion for hot air release and sound air circulation.
“Passive design aims to
optimize the building form ,orientation ,façade design and space planning
together with overall site layout to make maximum use of the natural
environment in order to provide occupant comfort with minimum use of energy
and mechanical systems. “
Summary and Conclusion
Passive control design may not
be the ultimate answer to satisfy occupants when it comes to outstanding
comfort. But, by taking full advantage of natural and renewable energy
resources before using any mechanical means or any active control system to
ventilate the space is a sustainable approach that would contribute in
mitigating climate change, reducing carbon emissions and even to zero energy
consumptions. With these issues confronting world today, architecture in the
Philippines must adapt or be responsive to the climate and the immediate
context of its environment. Eventually therefore, when all of these technical
norms and principles given are relatively and habitually observed, Passive
Design with prime considerations on natural light and air will
always be one Crucial Component of Change in the Cityscape.
Truly enough , this will make ARCHITECTS
AS CITY CHANGERS , indeed!
References and Suggested
Readings:
Department of Energy (DOE) –Guidelines
for Energy Conserving Design of Buildings-Updated 2007
DOE-National Energy Efficiency
and Conservation Program (NEECP)
DOE-Energy Management and
Energy Audit (PowerPoint Presentation)
DOE-Energy Reform Agenda
((PowerPoint Presentation)
UAP Memorandum Circular No. 08,
S. 2012
Internet Websites:
Natural ventilation: Stack
Ventilation
http://www.architecture.com/SustainabilityHub/Designstrategies/Air/1-2-.
http://www.humidifierinformation.com/optimum-humidity-levels.php
http://pinoygreenacademy.typepad.com/pinoy_green_academy/2010/01/the-first-ecohouse-in-cebu.html
http://en.wikipedia.org/wiki/Natural_building
http://en.wikipedia.org/wiki/Climate_of_the_Philippines
http://www.peaktoprairie.com/?D=205
Cross Ventilation in House
Designs for Natural Passive Air Flow
http://janderson99.hubpages.com/hub/Cross-Ventilation-in-House-designs...
http://www.sustainability.vic.gov.au/resources/documents/Air_movement.pdf)
What Rooms Do Not Require Natural
Light & Ventilation? | eHow.com
http://www.ehow.com/list_7597999_rooms-require-natural-light-ventilation.html#ixzz1zBEQHDXs
http://www.sustainableschoolswales.org/sustainable_design_options/buildings/passive_design/climate/index.php
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