Sustainable Design and Thermal Comfort Strategy: Cases of Urban “Affordable Housing” in Nepal
Introduction
Thermal Comfort Strategy is often an afterthought in the rush to provide low-cost shelter, yet it remains a pivotal factor in the long-term viability and habitability of urban housing.
In the context of Nepal’s rapidly growing urban centers, the disconnect between initial construction costs and lifelong environmental performance has created a crisis of livability for low-income households.This article provides a comprehensive analysis of the research conducted by Pratiksha Shrestha and Sushil Bahadur Bajracharya, published in the Proceedings of the IOE Graduate Conference, 2017.
By examining three distinct case studies of affordable housing in Nepal’s hilly regions, we uncover how a robust Thermal Comfort Strategy can transform affordable housing from mere shelter into sustainable, healthy homes.
The Sustainability Gap in Urban Affordable Housing
Housing is frequently defined by its price tag, with environmental and social considerations treated as separate, optional luxuries. However, true affordability extends beyond the initial investment; it encompasses the ongoing cost of living, health impacts, and social integration.
According to Nepal’s Shelter Policy 2012, the country faced a housing deficiency projected to reach 900,000 units by 2023, requiring approximately 90,000 new units annually.
In this urgent landscape, providers often prioritize speed and low initial costs, resulting in structures that fail to address thermal discomfort or socio-cultural needs.
The study highlights that while some community-level projects claim success, many suffer from poor building performance due to inferior materials and compact designs.
For instance, affordable housing projects for flood victims in Haripur were abandoned because they were located too far from city centers, illustrating that location and accessibility are just as critical as the physical structure.
To address these gaps, the researchers developed a framework of 21 indicators across economic, environmental, and socio-cultural pillars to assess the sustainability of existing affordable housing.
This holistic approach is essential for developing an effective Thermal Comfort Strategy that serves the diverse needs of low-income occupants.
Methodology and Case Study Selection
To understand the real-world application of sustainability principles, the research employed a case study methodology focused on urban hilly regions of Nepal. Primary data was collected through field observations, occupant questionnaires, key informant interviews, and indoor temperature recordings.
This mixed-method approach allowed for a nuanced understanding of both the physical building performance and the subjective experiences of the residents.
Three specific housing projects were selected for their unique characteristics:
- Paliphal Housing (Kirtipur): Chosen as the first project to address urban poverty with an environmental focus, particularly in water management and waste treatment.
- Karmachari Sanchayakosh Housing (Pokhara): Selected for its use of sustainable building materials and technologies, providing insight into material impact.
- Samabesi-tole Housing (Pokhara): Included due to its community participatory design approach, highlighting the social dimension of sustainability.
By comparing these diverse models, the study aimed to investigate the relationship between building materials and indoor thermal environments, ultimately proposing a refined Thermal Comfort Strategy for future developments.
Analyzing Passive Design and Building Materials
The Role of Orientation and Density
Passive solar design is a cornerstone of any effective Thermal Comfort Strategy, yet the study found it was largely neglected in the selected cases. While all dwellings had access to winter sunlight due to low-rise planning and open spaces, the orientation of longer walls toward the south—a critical factor for winter heat gain in Nepal’s hilly climate—was rarely optimized.
In Paliphal Housing, for example, the planning did not account for the prevailing west-to-east wind flow, missing an opportunity for natural cooling. Conversely, Samabesi-tole Housing benefited from a sloped site that allowed prevailing winds to enhance summer comfort.
Density also plays a significant role. Paliphal Housing exhibited the highest density (144 units per hectare), yet its arrangement around open spaces prevented it from feeling overcrowded.
This suggests that high density, when planned correctly, can coexist with adequate open space, a key component of a sustainable Thermal Comfort Strategy at the neighborhood level.
Material Impact on Indoor Temperatures
The most striking findings related to building materials. The study revealed a direct correlation between material choice and indoor thermal discomfort. Paliphal Housing utilized 4-inch-thick burnt brick walls, which have a high U-value (heat transfer coefficient), allowing easy heat penetration.
More critically, the use of Corrugated Galvanized Iron (CGI) sheets for roofing on upper floors resulted in severe thermal fluctuations.
Data recorded on March 3, 2017, showed that the top floor of Paliphal Housing, roofed with CGI, was significantly hotter than the ground floor, which had an RCC slab. The U-value of CGI is approximately 61 W/m²·K, compared to 4.5 W/m²·K for a 110 mm RCC slab.
This high conductivity causes instant heat gain during the day and rapid heat loss at night, creating an unbearable indoor environment. Occupants in both Paliphal and Samabesi-tole Housing expressed a strong preference to replace CGI roofs with RCC, despite the higher cost, underscoring the failure of current material choices in delivering a viable Thermal Comfort Strategy.
Developing a Holistic Thermal Comfort Strategy
Based on the empirical data and occupant feedback, the study proposes specific material and technological interventions to enhance indoor thermal comfort. These recommendations form the core of a practical Thermal Comfort Strategy for affordable housing in Nepal’s hilly regions.
Recommended Walling Materials
To reduce heat transfer, the study recommends moving away from thin burnt brick walls. Instead, it advocates for:
- 8-inch-Thick Hollow Concrete Blocks (HCB): With a U-value of 1.89 W/m²·K, HCBs offer superior thermal resistance and time lag, keeping interiors cooler in summer and warmer in winter.
- Compressed Stabilized Earth Blocks (CSEB): These can be produced locally, reducing transportation costs and carbon footprint while providing excellent thermal mass.
Innovative Roofing Technologies
Roofing is identified as the most critical element in a Thermal Comfort Strategy because it is directly exposed to solar radiation. The study recommends two primary solutions:
- RCC Filler Slabs: For new constructions, using RCC filler slabs with 4-inch hollow CSEB as filler material is highly effective. This technology is cost-effective, easy to maintain, and provides the added benefit of a private terrace, a feature highly demanded by occupants.
- Ventilated CGI Roofs with Insulation: For existing structures or budget-constrained projects, simple interventions can mitigate CGI’s drawbacks. Installing a soffit vent creates a ventilated roof system, allowing hot air to escape. Coupling this with an insulated false ceiling—such as a bamboo mat supported by bamboo frames, topped with sacks of empty plastic bottles—can significantly reduce heat flow. This low-cost insulation technique traps air, reducing heat gain in summer and heat loss in winter.
Beyond Thermal Comfort: Economic and Social Sustainability
A comprehensive Thermal Comfort Strategy cannot exist in isolation from economic and social factors. The study emphasizes that affordability is not just about construction costs but also about location and accessibility.
Accessibility and Economic Opportunity
The location of housing profoundly impacts its sustainability. In Paliphal Housing, over 60% of occupants traveled more than 4 km to work, relying on motorcycles and public buses, which increased their daily expenses and time burden.
In contrast, Karmachari Sanchayakosh Housing, located in Pokhara’s city center, offered high accessibility to jobs and markets, with most residents traveling less than 2 km.
The study concludes that affordable housing must be situated within 4 km of employment hubs and within 500 meters of essential facilities like bus stops and groceries.
This proximity reduces transportation costs, making the housing truly affordable and supporting a sustainable Thermal Comfort Strategy by reducing the overall carbon footprint of the household.
Community Participation and Adaptability
Social sustainability is enhanced through community participation and housing diversity. The study notes that none of the case studies provided rental options, limiting flexibility for smaller households or those with fluctuating incomes.
Incorporating rental units and varying bedroom counts can cater to diverse needs. Furthermore, incremental housing designs that allow for internal modifications while maintaining exterior aesthetics can empower residents to adapt their homes over time, fostering a sense of ownership and community bonding.
Conclusion
The research presented in Sustainable Design and Thermal Comfort Strategy: Cases of Urban “Affordable Housing” in Nepal offers a critical roadmap for policymakers, architects, and developers. It demonstrates that true affordability requires a shift from short-term cost minimization to long-term value creation.
By integrating passive solar design, selecting materials with low U-values such as HCB and CSEB, and implementing innovative roofing solutions like filler slabs or ventilated CGI systems, we can create homes that are not only cheap to build but also cheap to live in and comfortable to occupy.
Ultimately, a successful Thermal Comfort Strategy is multidimensional. It combines technical solutions for indoor climate control with strategic urban planning that prioritizes accessibility, economic opportunity, and community engagement.
As Nepal continues to urbanize, adopting these evidence-based strategies will be essential for creating housing solutions that are environmentally sustainable, socially inclusive, and thermally comfortable for all residents.
The insights from this study serve as a vital reference for anyone committed to improving the quality of life in urban affordable housing.
Also read: A Policy Study on Urban Housing in Nepal