Introduction

The 2020 Global Poverty update report 1 estimated that, in 2018, 46.2 % of the world lived on less than 5.50US$ per day, with an increase of 0.2 % since 2015, of which 12 % lived in slums 2. Poverty is a multi-dimensional problem, not only related to effective income, but also with access to a job, to education, to health care, as to social life. In Brazil these effects can be detected in the urban tissue where, from one side the typology of the closed condominium, an illusion of living in a private island, excluded from the outside chaos 3 on the other, the informal constructions, self-built, filling the urban voids 4. Today poverty reduction is suffering a reversal tendency due to the Covid-19 pandemic and its global economic effects, armed conflict and climate change 5. In hot countries around the world, the type of poor construction shows differences marked by culture, natural resources or by its industrial development, which may influence the indoor behaviour 6. Low thermal mass envelope in poor houses, in high outdoor temperature, tend to warm up the indoor from levels of comfort 7. This unsolved and complex spreading reality may be urgently addressed.

Methodology

For the pursuit of the goal, have been used Research by Design (RbD) driven strategy 8, complemented by a scientific methodology, for experimentation and analysis. Both qualitative and quantitative approaches informed and defined the extents and the limits of the investigation hypothesis. A constant realignment of the construction of the artefacts, based on trial and error, was followed, to validate the proposed solutions 9. The research is divided into 2 phases organized into 3 different stages 10, repeated 2 times (fig.1).

In the first stage, the literature review was complemented by in-situ research. This approach informed the question formulation, allowing the development of the first Design stage, characterized by the design project of a solar chimney. The first design proposal for improving comfort by evapotranspiration, showed uncertain results, suggesting the implementation of different strategies to be explored individually and combined, compelling to return to the pre-design stage to re-design and verify the effectiveness of the new proposals. To overcome the limits of the campaigns results, has been applied a dynamic simulation, using EnergyPlus v.8.7 11, to evaluate effectiveness in multiple hot climates.

Brazilian experience phase

On a planet of slums, how is a poor house? How is built? How is lived? How is its thermal space? How much could be the budget for improvements? What strategies may be effective to improve comfort in such communities? This phase objective was set to answer the many questions raised.

The first phase was held in Fortaleza and Sobral (1+2 years), Brazil. Establishing contact with the poor community, during the first months, seemed an improbable goal to achieve, in a violent and suspicious environment such as Fortaleza 12. Yet I could find a job (paradoxically) in the front line of a Governmental expropriation in 5 slums. Each had a formal representative, who maintained the team safe, guiding us through the community, during sunlight, and mediating with the residents. I visited more than 200 houses and spoke with their owners, observing the traces of living.

The poor permanent houses, have a spontaneus genesis and are built outside the regulations. Starts as a unique piece, that will be extended by the means and the time of the householders and, even when achieving the last stage of the shelter (the brick house, focus of this investigation), is always evolving, thus unfinished and ephemeral, like life itself 13. The technique is the most rudimentary, the materials are the cheapest 4. The most common type of envelope is made by a single layer of brick, commonly shared with the neighbour, rarely plastered on both sides, that forms the house muscle, without bones (fig. 2). On the walls, a wood structure is settled, on which a ceramic roof tile lies directly, covering the internal space (Tab. 1).

The internal distribution is organized by the structure support. The entrance is used, at night, as shelter for the bike or the motorcycle owned. The rooms, are often open on the roof level, allowing air circulation. The bathroom is located close to the outdoor sewage solution, with no relationship with any internal space. Houses have hooks on the wall to support the hammocks. Each space support multiple usages. Most owners stores used or found construction materials to be employed in the future.

If Occidental architecture works on the transformation of the environment to adapt it to human’s necessity, this survival architecture tries to contain transformations, implementing the necessary for a sufficient favourable surviving conditions 14.

Soon I understood that I have to reformulate my RbD approach to adapt and operate in this context, using what Levi-Strauss called the “first science”: the bricolage 15. I had also to re-evaluate, in this type of fragmented construction, the concepts of (dis)order and chronology. A setup of hypothesis pre-requisite was sketched: the roof, responsible for 50 to 70% of the indoor thermal behaviour 16, was set as the envelope side to be improved; all strategies should be effective, low-cost and suitable for self-construction in a DIY mode.

In Sobral, supported by the University of Architecture INTA, I started contacts with the resident association of the community of D. Expedito, located on the left side of the Acaraú river, upgraded in 2000 with basic sanitation and road infrastructure 17. I was allowed to survey 10 houses and interview the owners. Houses overheat during the day and use as a mitigator tool a simple fan.

The first strategy proposal was inspired by Fathy’s houses, where natural ventilation acts as a cooler, improving comfort through evapotranspiration. A portable plug-in rooftop solar chimney (CHS), to induce indoor ventilation, using cheap or recycled materials locally available was studied, designed and prototyped (fig.3).

The project was presented to the community with the idea of creating a workshop with the interested residents, free of charge, to build up to 5 CHS and install them. Only Lucineide’s family agreed, being unable to help in the construction of the artefact. During an architectural summer workshop, with a group of 5 students, was built the CHS2 and installed. After four months of use, the qualitative results collected were positives, reporting improvements in indoor comfort. Nonetheless, a 6 days measurement campaign showed non-conclusive results, appointing to a slight indoor temperature increasing and the introduction of complementary strategies to achieve the goal 18.

Note: The day before the installation I have been called by Lucineide’s husband who wanted to cancel the experiment. He was ensured that no cost will be supported by his family. At the end he asked me if I was an inventor, and finally agreed.

Portugal Experimental phase

The research continued at the University of Lisbon, Faculty of Science, where was built, using bricoleur technics, a test cell to install strategies and measure it in a controlled environment. The CHS3 was improved and resized. As complementary strategies (fig. 4) have been selected and studied, for their low cost and simple construction: a reflective roof coat strategy (Albedo); Radiant Barrier insulation (RB). All strategies have been implemented and evaluated.

The data collected for each strategy were non-comparable, suggesting a better performance of the radiant strategy over the other strategies. A simplified dynamic simulation to validate the model was performed with no conclusive results 25.

For the third cycle, a second test cell was built beside the first one, to be used as the default model cell: the strategies were reviewed. A design of a TetraPak recycled insulation board (TI) and a simple tube pipe chimney (PC) for natural ventilation was implemented as strategies (fig.4). A validated simulation model allowed to apply the suitable strategies in multiple hot climates.

Results

RB and TI, presented in the experiment a maximum decrease of interior operative temperature of 2.5ºC, at 27.5ºC outdoor temperature, and a 2.3ºC at 26.6ºC, respectively, with an increase of thermal comfort period up to 37.8%.

The introduction of natural ventilation, through the PC and the CHS3, proved ineffective during the day. The validated simulation applied, presented a maximum decrease of 3.45 ºC with RB and 3.39 ºC with TI (fig.6). Have been noted overheating during the night and corrected with a single window opening, (0,40m2), only for night cooling (fig.5).

Conclusions

The results show that Radiant Barrier (RB) and Tetrapak insulation board (TI), at the cost of 5€/m2 and 1-2€/m2 (depending on the scotch tape price and quality) respectively, act as a mitigator and must be accompanied by night cooling. Both materials can be used as roof insulation, allowing to re-shape internal spaces, both physical and thermal, at a very low-cost price, as verify the behaviour of an ETIC system built with Tetra Pak.

The solar chimney proved to be non-effective in hot climates, inducing the hottest outdoor temperature inside the house. Nonetheless, this artefact should be studied in different environments and climates, using a controlled ventilation, with cooler airflow.

From my personal experience, such improvements should be introduced in the community through resident associations, by recognized organizations (Universities, ONGs, etc...), to access this context and to aid in their organizational process. Involving actively the population directly concerned 26, giving them the tools to upgrade their environments, maybe a strategy, while global approaches to eradicate poverty are implemented.

Note: All Figures rights belong to the Author, except graphics on Fig. 4, referenced on 23 and 24.