Low-cost Methods for Improving Brazilian Informal Housing

When:

Fall 2015

My role:

Building Science

HVAC Engineering

Undergraduate Researcher

Tools used:

eQuest

Climate Tool

The Story

In October 2015, I traveled to Brazil as an architecture and architectural engineering student to examine architectural opportunities to help improve the lives of low income residents.

São Paulo, Brazil has experienced a tremendous urban expansion over the last half of the century. This, coupled with economic turmoil/instability has led to undesirable outcomes – notably, the rise of mass scale informal housing called favelas. Favela neighborhoods appear on land desired by no one else, near creeks and in risky floodplains where no financially stable homeowner would invest in. Those who have no choice build undocumented homes on these lands.

 

During my trip, I spoke to residents of these buildings and toured these thriving neighborhoods which seemed to boast of human ingenuity around common issues like lack of secure electricity. Yet, these efficiently constructed buildings are built by experienced masons and builders whose building practices are rigid (for fear of structural safety) and do not explore optimized construction. Furthermore, these buildings exist in São Paulo’s somewhat temperate climate, and do not use mechanical heating/cooling/ventilation. The sacrifice is that there may be many days where the temperature and humidity is well beyond the thermal comfort region. From my studies I knew the proven impact that poor indoor thermal comfort can have on one's quality of life and cognitive performance - both things that, when poor, can hinder one's ability to climb out of their socioeconomic bracket.

Sketches from me of the typical wall construction of the favelas

My model and analysis of the typical two-story favela construction

The Problem

 

Since the inhabitants do not have the financial means to install a mechanical system in a building that was never designed to accommodate for one - how could I help improve the mental and physical well-being of the favela community and provide a safer home environment?

Plus, a cost-effective passive solution that does not require mechanical heating/cooling would be more sustainable.

 

The Approach

Apply energy modeling + mechanical engineering + architecture

I decided to apply both my architecture background and engineering background to tackle this problem. The goal of this project was to design and analyze cost-effective solutions through building science and computer building energy simulation in order to improve indoor climate of favelas.

 

The Steps

I first began by examining if there was a problem to begin with - I used several tools to plot the climate of São Paulo to examine existing conditions.

 

Weather data overlayed onto psychrometric chart

 Wind Rose of São Paulo

What I found was that much of the year saw temperatures which were too hot or too cold, and generally very humid. Unfortunately, we could not rely on natural ventilation because the wind rose analysis returned that the wind was generally too low in speed.

 

Next, using eQuest, I modeled a standard favela building, applying my knowledge of its construction. What I found was that MUCH of the year, the indoor conditions inside one of these favelas were outside what we would typically consider to be within thermal comfort regions. In the figure on the right below, the area between the dashed lines indicates the acceptable region - each blue dot indicates a simulated day's temperature and many of the dots are outside of the acceptable region.

 

My drawing of a typical favela construction

Indoor temperature results plotted against thermally acceptable region

Solution 1: Design a double wythe (or double layer) wall

By increasing the wall thickness to include another layer of structural clay tile, I could take advantage of increasing thermal mass (which helps dampen extreme temperature swings). Double or triple layer construction is actually quite common in masonry in many parts of the world. As you can see in the bottom right figure, the orange points represent the new simulated days which more closely fit within the acceptable thermal comfort zone.

 

Proposed change to typical wall structure

New indoor temperature results plotted against thermally acceptable region

Solution 2: Throw some shade on it

Because retroactively adding another layer of wall seemed infeasible, I tried another design which involved casting the entire building in shade to protect from solar radiation. Constructing a whole-building shade feature turned out not to have as noticeable of an affect.

 

Proposed whole-building shade

New indoor temperature results plotted against thermally acceptable region

Solution 3: Add some fans

One way of increasing indoor thermal comfort is by increasing the air exchange rate - which is the amount of times the volume of air inside the home is replaced by outside air. I mentioned before that natural ventilation couldn't be used to do this - but I wanted to see if using a fan to increase air ventilation would help. It turns out that, although this is the only method that uses some amount of electricity, the effects were very promising as increasing the air exchange rate (ACH) leads to a significant increase in thermally acceptable days.

 

Using simple equations used in sizing mechanical ventilation requirements for buildings, I sized the fans that would be needed for this purpose.  Using energy simulation, I verified that keeping the fans running was not too prohibitive, especially when considering the end users of these architectural solutions.

 

Conclusion

Depending on if the favela being constructed is new or existing, I came to the conclusion that low cost, simple changes in the wall construction methodology or adding two fans into the buildings can lead to a massive increase in thermal comfort of these informally constructed homes. 

The resulting findings were published in “Planning versus Participation: A False Brazilian Dilemma" where I am listed as a student contributor.

 

Copyright © 2019, Julia Park

julia.park@berkeley.edu