January 8th, 2009
cross ventilation in tropical climatesDear 2students,
What is your question?
Regards,
ScriptorHi 2students,
Your question is not long on specific requirements, so I'll answer it
as generally and completely as possible.
First, a definition of terms - what are tropical climates and what is
cross ventilation?
According to Square One, an Environmental Design Website, compiled by
Dr. Andrew Marsh and Caroline Raines of Square One Research and the
Welsh School of Architecture at Cardiff University, tropical climates
have year-around average temperatures in excess of 18 degrees Celsius,
and generally extend northward and southward from the equator to
"about 15 to 25 degrees of latitude". Most of these areas are in
Central Africa, Southeast Asia and Central America.
Cross ventilation is simply a building design methodology in which the
structure is constructed so as to maximize the movement of air through
the building in order to "reduce internal temperatures [and] maximize
ventilation rates to increase the effectiveness of sweat evaporation".
http://www.squ1.com/index.php?http://www.squ1.com/climate/koppenA.html
According to Sam C. M. Hui at the University of Hong Kong, because of
the almost constant heat and frequent high humidity, cross ventilation
is far more important in the tropics than in other climatological
areas. This architectural emphasis differs somewhat from other climate
zones in that cross ventilation always should be maximized in the
tropics, whereas in other zones, it needs either to be minimized
during some high velocity wind events, or blocked altogether in colder
seasons.
http://arch.hku.hk/~cmhui/teach/65156-7c.htm
How is the best cross ventilation achieved? It is done through (1)
careful building design and by (2) appropriately positioning the
building to make maximum use of natural air movement. Cross
ventilation design is driven by the understanding that, as stated by
Australian architect Ann Roche, "air will not enter the building
unless there is a passage of exit." In other words, simply having an
opening (door, window, etc.) facing the direction of the prevailing
wind will not create cross ventilation because without an exit point,
the air will not flow through the building.
Further, according to Ms. Roche, "All rooms should have ventilation
points to facilitate cross ventilation. If not the room will get
hotter as the day progresses." She further reminds that "Even
bathrooms need more than a mere porthole often found in temperate
areas. It is the dampest room in the house and in a humid climate that
means mould."
In addition, "One of the biggest enemies of cross ventilation is the
hallway. These should be kept to an absolute minimum in a tropical
home. They are dark hot holes which prevent movement of breezes freely
though our living spaces. If you are designing a home from scratch try
alternative access means to bedrooms other than hallways. Wide
verandahs make great tropical halls."
http://www.cichappell.com/bkhomes/lifes_a_breeze.htm
What are some other general principles to include in design to achieve
maximum cross ventilation? The following is from Marsh and Raines of
Square One:
1) use of large doors and windows to promote cross-ventilation,
2) open planning and wide, free spaces between buildings,
3) raising building on stilts to cool floor and raise windows for
better ventilation,
4) large overhangs to protect from internal spaces from solar
radiation,
5) use of sliding screens to protect from storms and insects at
night,
6) use of low thermal mass materials to minimize heat storage,
7) use of double roofs with two layers and a ventilated air space,
8) use of highly insulating materials in roof,
9) use of maximum exterior wall with minimal number of interior
rooms, preferably arranged no more than one deep,
From Ann Roche:
9) vents at the ceiling spaces at the highest point in the roof
space,
10) if the ceiling is flat, some small louvred windows placed as
closely to the highest point possible.
Including those design features will facilitate cross ventilation, but
to maximize it, certain ideas should be incorporated into a building's
location and orientation. These, again are from Marsh, Raines, and
Roche:
1) orient the building so that the prevailing breeze blows parallel
to the line of ventilation entrances and exits
2) try to incorporate exterior shaded areas that wind can blow
through before entering the building
3) if a pool is to be present, situate it on the upwind side of the
building so the wind can blow across it before entering the building,
thus creating a natural "air conditioning"
Here's are a couple more landscaping tips from Joan Bradshaw and Linda
Tozer:
4) don't plant trees with branches that may block wind from coming
into the building
5) use bushes to route wind up and into windows
http://edis.ifas.ufl.edu/BODY_EH215
And:
6) multiple buildings should be spaced at a minimum of five times
the building's height to allow breeze penetration
http://www.fao.org/docrep/T0521E/T0521E0i.htm
Here are some additional resources for you:
Passive design response for different climates:
http://216.239.33.100/search?q=cache:Xa7YmTgeMpQC:www.greenhouse.gov.au/yourhome/technical/pdf/fs11.pdf+%22cross+ventilation%22+tropical+climate&hl=en&ie=UTF-8
Technical Manual for Passive Cooling:
http://www.greenhouse.gov.au/yourhome/technical/fs15_a.htm
Passive solar house designs:
http://www.solarhouseday.com/examples/nt.html
Description of a traditional Malay house:
http://216.239.33.100/search?q=cache:wyrMmp4AkAwC:idrinfo.idrc.ca/Archive/ReportsINTRA/pdfs/v12n4e/110780.pdf+%22cross+ventilation%22+tropical+climate&hl=en&ie=UTF-8
A house in Bermuda:
http://www.vsba.com/projects/fla_archive/158.html
A Cuban housing project:
http://www.groundwork.org/cuba/pwt005.html
Design of houses in relation to climate:
http://216.239.33.100/search?q=cache:Xa7YmTgeMpQC:www.greenhouse.gov.au/yourhome/technical/pdf/fs11.pdf+%22cross+ventilation%22+tropical+climate&hl=en&ie=UTF-8
I believe I've provided a comprehensive overview of the architectural
relevance of cross ventilation in tropical climates, and the ways to
achieve it. If you have any questions about my answer or the links
provided herein, please use the Clarify Answer button to contact me,
and I'll get right back to you.
Thanks for using Google Answers,
ericynot-ga
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