Tempering the Temporary: Improving thermal comfort and safety in relief shelters
On April 12, 2015, a powerful 7.8 magnitude earthquake struck Nepal, four months before I was scheduled to start graduate school in the US. The earthquake and its aftershocks forced my family and me into a temporary shelter, where we ended up staying for about a month. Although we were safe there, everyone was exposed to a wide range of temperature swings: extremely hot during pre-monsoon summer days and chilly at night. My experience of living in a temporary shelter and subsequent discovery that millions of people worldwide continue to live in such places for years on end motivated me to research ways to improve thermal conditions in shelters.
A temporary shelter is meant to serve as initial housing until a more permanent solution is found. It is the second phase of crisis recovery; the first is an emergency shelter (e.g. a tent or tarp) only meant to be used one to two weeks. Despite guidelines encouraging climate-responsive designs, similar temporary shelters like the one I experienced are frequently deployed globally across substantially different climates, resulting in anecdotes of unbearable interior temperatures that can compromise already-vulnerable users.
An example of this trending interest is the UN partnership with the IKEA Foundation to develop a flat packed pre-fabricated shelter to be deployed globally called Better shelter. According to interviews with organizations involved in this sector, current shelter responses are built under time and cost constraints so comfortable thermal conditions are not a high priority. There have been anecdotes of expensive pre-fabricated shelters that were helicoptered into a remote, high-altitude site later abandoned in the winter due to unbearable interior temperatures.
Evaluating appropriateness of commonly used shelters
Adaptive thermal comfort is a relatively new standard from ASHRAE (American Heating, Refrigerating and Air-Conditioning Engineers) that changes thresholds temperature based on average monthly outdoor conditions and is suited for naturally ventilated buildings. The threshold for regular ASHRAE thermal comfort standard stays the same throughout the year with temperatures ranging from 67°F [19°C] to 82°F[28°C] and humidity from 20% to 80%. In contrast, temperatures of 95°F[35°C] and 54°F[12°C] were proposed as the upper and lower "health risk" thresholds in temporary shelters to evaluate thermal safety. These limits are based on data suggesting that vulnerable members of the population, i.e. the elderly, young children and the sick, are susceptible to cardiovascular problems, strokes and other health risks in sustained conditions above or below this temperature range..
Thermal simulation was used to test the climate-appropriateness of 14 of the most common types of temporary shelter designs across 13 different climate zones. Five of the shelters and their respective climates were in South Asia – Afghanistan, Pakistan, Sri Lanka, Nepal, India, the rest were from Haiti, Ethiopia, Peru, Philippines and Indonesia. Evaluating these shelters based on adaptive thermal comfort threshold temperatures proved they were inadequate as interior temperatures frequently far exceeded these thresholds.
As a strategy to improve existing shelter design in cooler climates during winter, my team and I selected the A-frame shelters because of its simplicity and structural stability even for regions in earthquake zones. Then we added naturally insulating material like rice hulls, which are an agricultural waste. The initial design incorporated passive solar strategy, which involves storing daytime solar heat gain in concrete or mud floors, as well as strategically placed water barrels exposed to sunlight through window and roof openings. Heat gets re-radiated from all these elements at night when outside air cools down. Passive solar strategy coupled with roof insulation moved interior conditions out of the health risk threshold and approached adaptive comfort threshold. The thermal simulations helped determine the thickness of the rice hull insulation for optimal effectiveness.
In the field of building simulation and building simulation research, designers tend to focus on large, complex high-performance buildings. Yet, several compelling reasons exist for expanding this to include temporary shelter design. When dealing with living conditions for vulnerable populations (e.g. the elderly, sick, children), the health-related stakes are very high. Currently, cost is the primary driver of shelter design, but it has been proven thermal safety and comfort can be prioritized without significant financial increase. Climate data used for the simulations represent typical conditions based on recent 20 years, but these are anticipated to become more extreme in the coming decades.
This study demonstrated that simulation can be an effective tool to improve thermal safety and comfort in shelter design. Moreover, simulation can be a strategic policy tool to aid decisions to match shelter types to appropriate climates, improving both safety and the effective use of resources.
This is an excerpt from a paper with the same title coauthored by Prof. Holly Samuelson, Harvard Graduate School of Design- Joelle Jahn- WSP and Shreejay Tuladhar- Page Southerland Page published in Building Simulation 2019 Journal by International Building Simulation Associations (IBPSA).
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