Rice Husk Insulation System

Lack of thermal comfort and safety in Nepali homes and buildings is a critical issue. Our past research demonstrates that contemporary construction practices result in interior conditions that surpass the adaptive thermal comfort limits for the majority of the time and in extreme situations, exceed far from the comfort limits and into conditions that negatively affect the health of vulnerable populations i.e. the sick, the elderly, small children new mothers and pregnant women.

Most buildings in Nepal are unconditioned and lack any insulation. Contemporary buildings in Nepal are built with brick masonry and concrete structures with metal CGI roofs being prevalent among economically disadvantaged communities. They are built with little consideration for the local climate and materials availability despite the diversity in climate and geography in Nepal. The climates in Nepal range from the cold mountainous Himalayan regions, to hot-humid regions where temperatures peak at 40-45 ° C in the summer. The aftermath of the 2015 Nepal Earthquake saw a surge in these contemporary buildings, replacing the vernacular constructions, even in the remote areas, thus exposing more individuals to inadequate thermal conditions.

It is the economically disadvantaged (5.9 million below the national poverty line), marginal communities, and those living in remote rural areas are most impacted by the inadequate thermal conditions. They are more likely to be unable to afford fans, air conditioners, space heaters, or the energy costs to run these equipment and warm clothing to overcome the poor thermal performance of their shelters.

Public schools predominantly attended by the economically disadvantaged group (26,454 schools with 5.7 million students) are also impacted mostly due to their construction with metal CGI roofs and overall poor quality. There are frequent reports of the closure of these schools due to hot and cold waves, with the same school sometimes being closed during the peak summer and winter.

The perception of thermal comfort as a luxury for the affluent exacerbates the issue, as authorities and stakeholders often fail to recognize the health impacts of inadequate interior thermal conditions. Tragically, recent incidents such as the 34 deaths in post-earthquake shelters following the 2023 West Nepal earthquake underscore the gravity of the situation. The ambient temperature in the earthquake-affected areas never dropped below freezing hence the concerned authorities never assumed the situation would be as critical.

While Commercial insulation materials such as XPS foam, glass, and mineral wool are available, they are neither easily accessible nor locally manufactured in Nepal with availability limited to a couple of big cities. They are prohibitively expensive in comparison to the developed countries. Their manufacturing processes have a high carbon footprint and their constituents can lead to a negative impact on the health and wellbeing of the building occupants and installers.    Additionally, contemporary burnt brick-concrete construction uses up natural resources such as clay, river sand, and limestone which are getting scarcer leading to escalation in construction costs. Extraction of these resources also causes air pollution and environmental degradation locally, hence alternatives are needed in the Nepali construction industry.

Our solution aims to address the critical issue of inadequate thermal comfort and safety in Nepali homes and buildings by using wastes such as agricultural or fabric, specifically rice husk, for insulation, thus improving the thermal performance of the building envelope. The insulation is local, low-cost, bio-based, and carbon-negative which does not have a negative impact on the health and well-being of building occupants and installers. Rice husk, an abundant agricultural waste is often burned by farmers for disposal. Our solution is meant for renovating existing buildings as well as new constructions.

Rice husk even in its loose form is an excellent insulator with insulation properties similar to that of mineral wool (R-3 per inch /25mm). It is a Class I or A insulator meaning it does not catch fire easily and importantly does not spread it. It does not rot, develop mold, or react with metals. The rice husk to be used must be boiled to prevent weevil infestation. It is to be treated with inexpensive and safe chemical insect retardants, Borax and Boric acid specifically which also double as flame retardants.

We've developed a system to secure loose rice husk to any building surface, suitable for both retrofitting existing structures and new constructions. The system involves packing loose rice husk into specifically sized jute tubes. The insulation is packed into tubes of the desired diameter for the resultant insulation to be of specific consistent thickness. Otherwise simply packing rice husk into bags similar to earth bag construction leads to the insulation material settling at the bottom. Jute tubes of 5-6” thickness/ diameter were used in our solution. The insulation tubes are anchored to the building surface by nailing or tying with a rope depending on the nature of the building’s surface. In the case of masonry or timber walls, the tubes can be nailed. With a bamboo structure, the tubes must be tied with ropes to the bamboo structure. Finally, for the finishing, it can be plastered with mud or cement plaster while applying a chicken wire mesh beforehand which not only provides a substrate for easy plastering but also provides protection against rodents. The plaster rendering greatly improves the fire resistance of the insulation system.

 This system allows for easy adaptation, enabling substitution with other waste materials like shredded denim/ cotton, or wool based on local availability in regions where rice husk is not locally available.

The system’s cost of materials is extremely affordable ranging from NRS 35-10.75 per sq. ft (USD 0.26- 0.08) for the 5-6” thick insulation depending upon the price of rice husk locally. In comparison a single brick measuring 4” X 9” X 2”  (110 X 230 X 55mm) costs NRS. 16 (USD 0.12). In comparsion, commercially available mineral wool insulation costs at least 4 times for comparable thickness.

Additionally, we are producing structural insulated panels for a modular, factory-built approach to affordable housing, catering to a broader economic demographic.

Our solution serves the population living, working, or studying in buildings that are unable to provide thermal comfort and safety meaning buildings with poor thermal performance and without mechanical heating/cooling. However, we will be prioritizing economically disadvantaged populations and public schools they predominantly attend especially those in remote rural areas.

Improvement in the interior thermal conditions of the targeted population group not only improves thermal comfort but also reduces the health risks and (mortality rate) of the vulnerable population due to extreme weather events. Moreover, improvement in interior thermal comfort brings other advantages that have been well-researched. Studies have shown improved productivity, less stress, and improved academic performance in schools.  The solution attempts to provide equity in terms of thermal comfort which we the privileged often take for granted. Ultimately, the solution improves the quality and standard of life of the targeted group reducing energy poverty and thus also helping meet the UN’s Sustainable development goals. Our initiative also improves the resilience and adaptation to extreme weather events caused by climate change as Nepal experiences a higher rate of warming (0.5°C per decade) compared to the global average of 0.2°C per decade.

The initial research required to realize this solution was developed as the team lead’s graduate thesis at Harvard Graduate School of Design, where simulations and lab tests were used. Our organization has published additional research into the problem of lack of thermal comfort and safety in contemporary shelters and schools in Nepal as a response to which this solution was developed. We have the equipment and more importantly the know-how to monitor and evaluate the thermal performance of the building envelope. Moreover, the insights from experiences working in the building construction industry in the US and Nepal will be pivotal in adapting the latest body of knowledge and practice in building sciences from the US to real-world settings in Nepal.  

We believe now is the critical time to act and deploy this solution in Nepal as traditional commercial insulation materials such as glass and mineral wool haven’t become mainstream yet. There is a window of opportunity for rice husk- an agricultural waste a low-cost, biogenic, carbon-negative, and a healthy insulation material product to gain a significant foothold in the Nepali construction market. Such a scenario would be a unique feat for a bio-based product developed from waste. At present, globally there is a market for bio-based, healthy building materials.  

We have been recently commissioned for a pilot project to insulate a community building in Helembu a rural village 3hrs away from Kathmandu. We are in the process of deploying this solution to improve the thermal performance of post-earthquake shelters to the victims of the recent West Nepal Earthquake 2023 where we are already in talks with the locally elected ward chairperson of the most badly affected area. Additionally, knowledge will be transferred so that the locals can self-build.

  As thermal comfort can vary based on an individual’s ethnic, gender, cultural, and socio-economic background, our solutions will be adapted based on community feedback. Moreover, we hope to provide sufficient training, demonstration, manual and guides, and importantly inspiration so that the local community members themselves self-built this insulation system.

A prototype shelter with insulation has been constructed and successfully tested.  We monitored its thermal performances such as interior temperature, surface temperatures using equipments. We evaluated and analyzed the collected data and evaluated its thermal performance comparing it with that of an uninsulated shelter which we also built and monitored to act as a control for our study. This prototype was instrumental in figuring out the processes, the specific sizes of the jute tubes required as well as assess the costs and labor requirements. The prototype was successful in maintaining the interior temperatures within the thermal safety limits. Our team also occupied the shelter and slept in it to test its effectiveness.

Following is the summary of the measured performance.

When the outdoor air temp was a minimum of 7°C [44.6°F] at 7 AM, the mean surface temperature of the rice husk insulation walls were at 13°C [55.4°F]. The indoor air temp in the shelter was 13°C [55.4°F]. This is an increase of 5°C [10.8°F] in air temperature compared to the ambient temperature outdoors.

This is similar to more permanent brick concrete houses.

In comparison, tarpaulin shelter without insulation, the mean surface temperature was 2°C [35.6°F] and the indoor air temp was 7.7°C [46°F] with heavy dew indoors, and felt cold and uncomfortable.

Adaptive Thermal comfort is around 18-22°C [55-72°] for the month of December in Kathmandu Nepal. The cold Health Risk zone starts at temperatures below 12°[55°F] 2 (data suggests vulnerable populations, are susceptible to cardiovascular problems and strokes in sustained conditions below 12°C).

The graph above shows the recorded temperature curves. The purple line represents the mean surface temperature of the control shelter which was uninsulated with tarpaulin walls/roof. The diurnal temperature difference between the lowest and the highest temperatures measures 30°C[50°F] which is quite a lot and might explain why the health conditions of vulnerable populations living in these types of uninsulated  shelters.

We hope to gain guidance and mentorship in better developing our solution as a product that address the different segments of the market and create a more sustainable business model to support the innovation in our organization. We are also looking for technical assistance to develop additional products that build upon this solution and cater to different market segments.

  We hope to gain better visibility, marketing for our solution, and networking for better feedback and assistance with fundraising. We want to improve our message to be a better pitch to potential investors and stakeholders.

It has been our thesis that cutting edge simulation tools and building sciences used in the green building design industry has potential to create more impact if it is used for innovation in low cost or affordable housing sector. Currently this technology is limited in designing limited number of green buildings mostly in the developed world that are large, costly and complicated in terms of materials and building systems that deliver only a marginal improvement over the average new constructions.

Use of these technology and knowledge in extreme affordable housing sector will have more impacts in terms of improving the indoor comfort conditions, resilience to extreme weather and adaptation to climate change. Moreover its low cost has a higher probability for greater adoption leads to reduction in environmental impact and a healthier built environment. We are believers in the ethos of waste is raw material in the wrong place. Repurposing agricultural and other wastes into building materials and products is a strategy for keeping costs low that also promotes circular economy.

For about 1 year.

The background research that went into the solution started 9 years ago.

All of the team members are Nepali.

Our plan to become financially sustainable are to develop insulation products catering to different economic groups or market segments and use the profit to fund insulation contruction/renovation for the extreme low cost housing and public school sector. Profits will also be used to fund further research and innovation works.