In the UK, architects and engineers optimise building design to ensure that buildings are kept warm during the cold months. When British architects Andy Simmonds and Adele Mills of Simmonds Mills Architects were asked to design new housing and educational facilities for the Tanzanian Children’s Eco Village (run by UK based NGO, Islamic Help), they, alongside energy consultant Alan Clarke, came across the new challenge of optimising buildings for cooling in the year-round warm climate of Tanzania.
The Tanzanian Children's Eco Village was
established in 2012 to improve the lives of orphaned children in
Tanzania. The project encourages and prioritises sustainable,
environmentally conscious and affordable building practices.
As part of the sustainable directive, the experienced team at
Simmonds Mills Architects were interested in
exploring the opportunity of applying 'Passive
House' principles of energy efficiency and high comfort
levels to their building designs.
Passive House (or Passivhaus) is a
recognised global building standard for energy
efficiency. It was created as a framework for sustainable
building design, whereby the energy costs from heating and/or
cooling is reduced by passive benefits from a building's design. By
applying Passive House techniques to a building's design,
its ecological footprint will be reduced.
To be certified as a 'Passive House' a building must meet
certain energy efficiency requirements, including
coming under the 15kWh/ m2/yr cooling demand.
However, to achieve this standard in the Eco Village, the buildings
would have required expensive materials and air conditioning units
that would incur higher energy costs compared to using traditional
building strategies that would incur lower energy running
Coming up against the challenges of working with a cooling
climate and doing so in a resource-efficient way led the team to
come up with a low-cost, low-tech design which did
not require air conditioning for cooling and would provide
occupants with high levels of comfort.
To test the viability of the design, a test-build was
constructed between November 2017 and September 2018 using
locally sourced building materials. To assess how the new building
design and the building materials fared against the existing
buildings at cooling indoor temperatures, the team began
temperature and relative humidity monitoring using
Tinytag data loggers.
Gemini Data Loggers donated five Tinytag Plus 2
TGP-4500 data loggers-rugged and waterproof units
which are suitable for monitoring outdoor applications. Two data
loggers were placed in the test-build, two in a control house and
one was placed outside to track the outdoor conditions.
The data loggers were left in place for a monitoring period of
three months from November 2018 to January 2019 and yielded
promising results. Comparison of the data from the test unit and
the control house revealed that the bedrooms in the test
build were much cooler during the day than in the control
house, and that the test-building cooled much
faster at night than the control house.
However, the data also identified some problems in the
design of the test unit, such as a two-hour lag after
sunset where the bedrooms in the test building did not cool down
and remained at a daytime temperature.
Following these findings, Simmonds Mills
Architects adapted their designs by changing the sizing of
window and ventilation openings in the building and reducing the
amount of heat-retaining concrete blockwork used (reducing thermal
mass). Like the house designs, the design of the school also
includes an open ventilated and extended roof structure, providing
a passive route to vent hot air that otherwise
builds up above the ceilings, and large roof overhangs to shade the
windows, external walls and outside gathering spaces.
The combination of extensive shading, excellent cross
ventilation, hot air shedding combined with insect protection
measures and minimising thermal mass helps to keep internal
temperatures as low as possible throughout the daytime.,
In the house bedrooms, this helps to keep temperatures closer to
the night-time temperatures as they start to fall after sunset.
The preliminary work carried out by Simmonds Mills Architects
has been important to ensuring that the eventual buildings
use minimum energy while providing maximum comfort for
their occupants, while simultaneously promoting
sustainable, energy efficient, and affordable building
practices in Tanzania.