Shade: A Hot Climate Design Challenge for the 21st Century
David Baggs, CEO and Technical Director
As humans in a hot climate, we instinctively seek shade when
subjected to the hot sun. In our early buildings and even in the
adoption of traditional Middle Eastern Dishdasha and Abaya garments
or the traditional tropical ventilated double roof is the
instinctive acknowledgement that shade drives comfort in hot
Hot climates include both hot wet climates like the Middle East,
tropical and sub-tropical areas such as India, Asia and ,
Australia, Southern USA and South America, but also desert climates
like Australia, USA and Africa.
Figure 1: When it's hot
you need shade.
Early desert buildings limited window openings and created deep
set windows and occupied rooms within heavy mass walls. Tropical
buildings in having to cope with large volumes of water
instinctively added shade by including overhangs to keep out the
rain. This was all driven by people's experiences in trying to
reproduce environmental conditions that created comfort.
However with adoption of minimalism by modern architecture and
the rollout of minimalist, predominantly glass commercial buildings
globally, design strategies have been introduced into hot climates
that are not appropriate. Why have we let this occur?
Figure 2: Few modern buildings recognise the short
comings of glass as a radiant barrier and the benefits of well
insulated walls as dramatically as this SOM Bank Building in Jeddah
Part of the answer is due to the perception that new glass
technology is able to reduce heat to manageable proportions.
Another part is the perception that 'smart glass' allows
'affordable' air conditioning solutions. The reality of the
situation is quite different to the perception.
Figure 3: Grosvenor Square Building
Sydney: Architect Harry Seidler - one of the few Modern School
architects who adequately and consistently considered
In the peak of summer, in a hot climate typically the suns rays
exert 800-1000Watts per square metre on both people and buildings;
even in winter in such climates it is typically 500-800Watts per
square metre under a clear sky. This equates in summer to a total
heat load equivalent to a one bar radiator for every square metre
The reason this is important is that no matter how good
even double pane insulated glass is at preventing heat from the day
being conducted through the façade of a building, solar radiation
is a very significant additional load, that even the very best of
reflective and selective glasses cannot completely stop.
While the inset figures are from temperatures taken by me over a
period of time for a new office building in Jebel Ali in Dubai, the
same climatic conditions can be found in many locations around the
The Building has a glass façade and unshaded high performance,
reflective, double pane insulated glass, tinted in some areas and
clear in others. Typically the air temperature inside is invariably
21 degrees. If you consider the figures, you will notice that even
in winter when the sun is on the building's south face at 9.00am in
the morning the temperature radiating from the inside pane of glass
absorbed by the glass is 33 degrees! In summer at midday inside the
clear glass it rises up to over 37 degrees.
Table 1: External and Internal Glass and Air
Temperatures of Unshaded Office Building - Jebel Ali
Imagine yourself sitting at a desk near those windows, even
though the air conditioning is a chilly 21 degrees, the whole wall
next to you is like a huge radiator at 37 degrees- so even though
the air conditioner is working hard and from the room temperature
it appears that everyone would be comfortable- you will be sweating
and hot because the half of you facing the window is sitting in
front of radiator. Your body gets confusing signals, you start
sweating which in combination with the cold air temperature makes
you feel more comfortable - but even if your body is comfortable
enough not to move away from the glass, it is in a constant state
of stress and over time this may affect your immune system, lead to
a feeling of exhaustion and possibly even illness.
Heat loads on opaque elements in walls are more easily managed
with insulation. A relatively small amount of insulation is
sufficient to achieve this effect. 6 cm of polystyrene will reduce
the overall heat transfer coefficient through a concrete wall from
3.0 W/m²oC down to 0.5 W/m²oC, but glass is
The thing is, with windows, the air conditioning system still
has to deal with both the heat that does conduct through the glass
and the direct solar rays absorbed by the glass and reradiated from
the inside surface of the glass.
The whole issue of global warming generated in large part by the
use of energy and made much worse in recent years by the dramatic
rise in air conditioning means we need to reconsider the way
we think about how we use air conditioning. We need to think about
it as a means of last resort to stay comfortable in a difficult
climate and use every other means at our disposal to stay
comfortable without expending energy.
The first, most important thing we should do before even
designing the air conditioning plant is do everything we can to
design the building to use the least amount of energy possible.
Using passive means and to cut heat loads to the absolute minimum
and then sizing the air conditioning plant to suit.
The first and most important thing to consider in tandem to
reduce building heat loads is orientation and shading. Orientation
because if we align our buildings in accordance with the true
north/south, east/west axes, we also align the building with the
symmetrical path of the sun throughout the year and make it easier
and more cost effective to design simple fixed shading devices for
south and north faces.
In the Middle East because of the way the sun travels from north
to south, summer to winter at these latitudes, the east and west
faces are best shaded with moveable shades to maximise efficiency-
however the first skyscraper in Dubai - the Dubai World Trade
Centre Tower, although the appearance is not 'fashionable' now, is
proof that fixed shading can be designed to work well on all
aspects if one is prepare to investigate all options. Interestingly
- it also derives a strong Arab feel to the tower, something
unfortunately missing from most modern Arab skyscrapers.
Even though the north and south shading
can be fixed, optimum shading for each elevation is not the same.
On the south elevation in mid winter the sun is at 45degrees to the
glass so fixed horizontal shading needs to be as wide as the
distance between the shades e.g., a 1metre wide shade every 1 metre
or a continuous mesh or Arabic screen, whereas on the north in
summer, only very narrow horizontal shades of e.g. 10cm every metre
combined with regular deep vertical shading blades is needed. In
other climates the operable vertical or operable shades on the east
and west work well and only small horizontal projections are need
on the sun facing northern or southern faces (depending on which
hemisphere the building is in southern or northern
Figure 4: Close shading over Dubai World Trade Centre
There are some very sophisticated sunscreen design strategies
that exist around the globe and the need for solar shading does not
have to mean all buildings will look the same. It just means there
is a completely different aesthetic to explore and one that is
already being explored by some local architects. One such
innovative company is Ahmed Al Ali's award winning Dubai-based X
Architects with many examples of their work exhibiting a keen
understanding of the need for shade and creative, traditionally
rooted shade solutions evident in their designs.
Figure 5: Proposed Shaded Shopping
Centre Ahmed Al Ali- X Architects.
The new Abu Dhabi Urban Planning Council's Development
Regulations Code recognises the importance of external shade
and is requiring external building shading relative to the building
aspect with 'percentage shaded' specifications for each aspect.
The challenge this throws down to architects hereafter is how to
refashion the image of both skyscrapers and other buildings, to
integrate external shading within the aesthetic and technical
challenges of high rise and the design preconceptions that while
widespread must go the way of the dodo if we are not to!.
While visionary architects like Malaysian borne, London based
Ken Yeang in buildings like his Malaysian 'Fusionopolis' (it will
be Singapore's most eco-friendly building) have been working on
this conversion for years, the rest of the profession and building
owners now need to come to terms with re-creating and
re-interpretting the architecture of appropriately shaded modern
Ken Yeang Fusionopolis, Singapore