# A Review of Indoor Air Quality in Social Housing Across Low- and Middle-Income Countries
## 3 Results of the Literature Survey
### Housing Conditions and Socio-Economic Factors (HC&SeFs)  
The role of architectural design in improving natural ventilation is critical for maintaining IAQ [60; 61]. For example, research in Brazilian social housing found that the units did not meet natural ventilation standards due to inadequately sized and improperly placed fenestrations [60]. Brazilian low-income homes had an average of 13 m\({}^{2}\) of floor area per, but recent trends show a significant reduction to 9 m\({}^{2}\) per person in two room homes for families of four [75], in some cases to 10 m\({}^{2}\) per person [61]. Adding to these findings, [PERSON] et al. [62] used system dynamics modeling to show that increasing the window area to 3 m\({}^{2}\) and using EPS walls reduced peak indoor temperatures from 33.10 \({}^{\circ}\)C (for a 1.78 m\({}^{2}\) base case scenario window) to 27.87 \({}^{\circ}\)C, showing the role of design in mitigation of indoor overheating in tropical social housing. Certain architectural interventions, like reducing the aspect and compactness ratios, can significantly improve IAQ [61]. A study in Mumbai's social housing compared different layouts (base-case, Form A, and Form B) [61] and found that a staggered layout with lower compactness achieved higher wind velocities near windows, maximizing airflow, and providing better cross-ventilation. These improvements resulted in better IAQ and up to 40% better airflow conditions than the base case. Similarly, experimental wind-tunnel study [63], on low-rise H-shaped social housing buildings in Brazil, showed that cavity depth, building height and wind angles have a strongly impact airflow. Deeper cavities at 90\({}^{\circ}\) wind angles created stronger negative pressure (about 0.6 lower), which reduced airflow within the cavity and limited ventilation in those areas. At a 45\({}^{\circ}\) wind angle, the turbulence in deeper cavities improved airflow, helping cross-ventilation by creating pressure differences between cavity sides, which might reduce indoor pollutants. Taller buildings created stagnation zones at 20-40% of their height under 0\({}^{\circ}\) wind conditions where airflow slowed before reattaching higher up. This reattachment reduced swirling air near the ground, which might lower pollutant buildup outside and improve fresh air flow into the building if windows or vents are well placed. Socio-economic factors influence IAQ disparities, as shown in a study in South India [64] that found that women and children in low-income households were exposed to median PM2.5 levels averaging 1300 \(\upmu\)g/m\({}^{3}\) compared to higher-income households, which were exposed to median PM2.5 levels, averaging 510 \(\upmu\)g/m\({}^{3}\). Both values are much higher than the prevailing WHO guideline of 25 \(\upmu\)g/m\({}^{3}\). The study highlighted the impact of cooking practices on IAQ, with median PM2.5 concentrations significantly higher, at 1360 \(\upmu\)g/m\({}^{3}\), when the windows were kept closed during cooking activities, compared to 450 \(\upmu\)g/m\({}^{3}\) when windows were opened. These findings indicate that socio-economic factors and household habits play a significant role in the health risks associated with IAQ and respiratory diseases. In Nigeria, unreliable access to electricity and water supplies, forced residents to depend on alternative lighting, heating, and sanitary sources like personal power generators, candles, kerosene, and paraffin, all of which significantly degrade IAQ [65]. Most social housing residents were uncertain about the adequacy of natural ventilation and lighting in their homes, with only around 38% having access to public electricity and the majority relying on alternative sources. This insufficient infrastructure contributes to the decrease in living standards. Recent research further identified issues of inadequate ventilation and poor IAQ through quantitative analysis of Nigerian social housing residents [66].