House Screening - Biological and Environmental Control of Disease Vectors - page 135

Solar chimney

Reflection,
absorbance, emission

Corrugated
metal roof

Ceiling fan

The heat of direct sunlight is minimized
with small windows that do not face
the sun and with the overhanging roof

Compressed
stabilized soil
block walls

Fig. 7.4. The ideal house? Mosquitoes approaching doors and windows are prevented from entering by
screening material over the openings, and further discouraged by repellent plants. Solar-powered fans
and a solar chimney improve air movement indoors. The ceiling prevents any mosquitoes in the roof
space from reaching the room, and should absorb some of the heat from the metal roof. Carefully chosen
construction materials improve the durability of the house.

in Ghana and kept interior temperatures close to
shade temperatures even during periods of the
most intense radiation (Crane, 1970), but metal
roof materials are now more popular. Whichever
material is chosen, generous roof overhangs are
necessary to cast shade on exterior walls and
windows, and to protect the wall surfaces from
rain. If possible all wall and roof materials
should be treated to be fi re-retardant and
resistant to weathering, fungal and insect attack.
Ground-level fl oors should be made of concrete
slabs or stabilized earth. If there are wooden
raised fl oors then they must be high enough to
protect against low-fl ying vectors, termites and
dampness, and the boards must be tight-fi tting
to prevent vector house entry between the slats.
The ideal house should be built without
eaves, despite the potential confl ict with indoor
air pollution control in areas where cooking is
done indoors (e.g. the introduction of eaves
spaces has been shown to dramatically reduce
particulate matter indoors in Kenya; Warwick
and Doig, 2004). Chimneys, windows and
smoke hoods could compensate for the resultant
loss of ventilation when eaves are closed. A solar
chimney might be the most appropriate method
of increasing ventilation. Painted black and

heated by solar energy, the chimney would
become a collecting point for warm air, creating
an updraft in the room below that would disperse
the hotter air from the chimney vent. An
alternative would be to use a cooling tower that
draws incoming air down into the room by
cooling it using evaporative pads on top of the
tower. However, this approach, used in parts of
Mali, might also draw high-fl ying mosquitoes
into the house with the cool air, and requires
that the pads are frequently watered. With either
technique there is a new entry point for vectors
that must be considered. Either the chimney
itself must be screened (as was done in Italy by
Celli, 1901) or a ceiling below the chimney must
be installed. The increase in ventilation from the
use of the chimney must be considerably greater
than the decrease caused by the ceiling, and this
merits careful investigation. The ceiling itself
should be made of PVC-coated fi breglass or
other fl exible long-lasting tear-resistant material
of a density and mesh size maximizing venti-
lation while small enough to prevent vectors
passing through.
A one-way mesh ceiling would trap
mosquitoes in the roof space, yet might allow
mosquitoes in the room space to exit into the