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two research projects over two years investigating the
environmental performance of lightweight emergency structures
have been completed.
funded by
EPSRC"
and
hunt technology
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overview
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although tents are not the ideal shelter solution for displaced people, especially
in cold climates, there are cases when political and practical reasons force the
implementation of such a shelter solution.
since 1998
shelterproject.org
has been working on the insulation of
UNHCR
and
ICRC
tents using a shelter liner made from high-tech fabrics.
prior to the work of
shelterproject.org, it was believed that insulating shelters
could make substantial fuel savings. In practice, fuel availability for IDPs
is often extremely limited. critically, a practical set of shelter priorities needs
to be established.
- firstly the body must be kept warm
- secondly the surrounding air should be kept warm to reduce the respiratory health risk of occupants
fig. 1 shelter priorities to safeguard health against climate
project history
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shelterproject.org has conducted tests
in cold storage warehouses, car factory wind tunnels,
and in the UK field, backed up by computer modelling.
with the support of
ICRC,
shelterproject.org has conducted field research
visiting sixteen camps in 2002, and twelve in 2003.
a questionnaire was conducted in Afghanistan (Herat, 2002), Eritrea
(Gash Barka and Debub districts) and Afghanistan
(Kabul, Herat, Kandahar and Bamian, 2003). further casual observations of refugee
shelter were made in Chad (2003) and Mozambique (2002) where project staff
were working on field missions with
UNHCR
and
MSF-belgium
insulated shelter liners of two different types have been
taken to the Panjwai camps in Kandahar, Afghanistan. new designs of tents with
different liners have also been tested in Bamian, Afghanistan, for buildability and
occupant use.
direct comparisons of thermal performance between field and laboratory conditions may
not strictly be possible or relevant due to the diversity of shelters in the field and
the variation in occupant habits. instead comparative testing under the same external
conditions using both steady state tests and the occupancy model that has been
been identified as the best way of comparing different shelter solutions.
project results
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thermal comfort
the thermal capacity of a tent is relatively low, compared to the air change
rates and conduction heat losses to the ground and air that it experiences.
UK winter tests with no wind and limited flooring indicate that thermal equilibrium
can be reached in less than two hours. as a result comfortable internal temperatures
in cold climates can only be maintained when there is an internal heat source.
in hot climates, tents reduce solar gains, provide
improved privacy and dignity for occupants as well as protection from disease
vectors.
in cold climates liners can reduce heat loss through
conduction and radiation as well as infiltration. in order to
ensure survival, the primary priority is to keep the body warm.
this is most simply achieved through adequate clothing during the day
and sufficient bedding at night. it should be noted that good mattresses
are particularly important.
laboratory work conducted in UK indicated that heat loss due to infiltration
was significant, especially under strong winds. field observations indicated
that leakiness of tents in windy conditions was of concern to IDPs, many using
limited spare material to block draughts in tents.
a significant amount of infiltration heat losses for a tent are through
the tent canvas. infiltration heat losses rise in importance as the exterior
wind speed rises. it is here that a liner is important in reducing heat
loss as it can reduce air flow through the tent membrane as well as
creating an air gap between the fly sheet and the tent liner (which
can act as an effective inner tent.)
thermal stratification appears to be an issue when there is a signifcant heat
source in a shelter, but not in occupied unheated tents. insulating a liner
more heavily at the roof will lead to an improvement in performance only
when the tent is heated.
liner use and buildability
field tests in Kandahar (2003) and Bamian indicated that some of the liners
developed were too weak. the liners were however used as anticipated and not
cut up for use as bedding. lighter weight liners were easier to erect.
stoves
efficient stoves are essential part of cold climate strategies to ensure thermal
comfort.
relief budgets vary and so does the provision and availabilty of fuel wood.
IDPs in Afghanistan and the highland areas of Eritrea were seen to suffer
from a severe shortage of fuel, (surveys indicated that up to 2kg of fire wood
per person per day was being used). in many cases, people had to walk for five
hours to collect wood. As a result many families start cooking just before dawn
so that heat from cooking can also provide warmth when the night is at its coldest.
In some cases, small amounts of fuel were burned during the night. Strategies to
improve thermal comfort must ensure that internal shelter temperature does not
fall too low, and more critically, at the coldest times of day, prevent body
temperatures from falling too. in practice, with limited fuel availability
this must involve good bedding and clothing as a priority.
further work
despite the improvements made in understanding, the exact performance of
tents and tent liners is complex and not fully understood.
shelterproject.org
remain involved in research and development of improved tents and tent linings.
improvements
in understanding will lead to improved shelters for those most in need.
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documents
relating to this project
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acknowledgements
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This work has been largely funded by
EPSRC
Hunt Technology
in addition shelterproject.org
would like to thank the following companies for their support;
Destex S.A, Switzerland,
Gemini Data loggers, UK,
Sea France, UK,
Web Dynamics, UK
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