Insulating Buildings with By-Products of Rice Cultivation

Lessons and Inspiration from the SURF Renovation Lunch

At previous online events, EUKI project SURF had already explored the use of climate-friendly building materials such as clay, straw, hemp and paludiculture plants in order to offer inspiring examples of circular and sustainable construction and renovation.

At the latest SURF online Renovation Lunch, SURF had the opportunity to host Alessio Colombo, the co-founder of Ricehouse. With their projects the Italian benefit corporation managed to absorbe 266 tonnes of carbon dioxide in 2021 (the equivalent of more than 50,000 planted trees), 765 tonnes in 2022 and 1,200 tonnes in 2023. How is this possible?

As consultant and implementer, Ricehouse is working with municipalities and artists to retrofit public buildings with by-products of rice. They manufacture insulating materials, plaster and outdoor floor tiles made of rice husks or rice straw.

Insulating with rice by-products solves a double problem: GHG emissions in construction and agriculture

1. Construction related emissions: In Europe, the construction industry is responsible for one third of all waste as well as for 36% of the emitted carbon dioxide additionally to the emissions due to the heating and cooling of buildings. That is why the production of building materials generates huge amounts of carbon dioxide: half of the CO2 emissions in the building sector is emitted before their construction. This can be reduced by using recycled and/or natural materials (wood, clay, straw, etc.) – Ricehouse has chosen to do the latter.
2. Agricultural emissions: Currently, the agricultural by-products, rice straw and husk, are burned. Yet, the burning releases carbon dioxide and harmful substances.

Solution: If rice straw and husk are used as building material rather than being burned, they can sequester significant amounts of carbon dioxide in our buildings.  

What makes rice by-products a sustainable material?

• Their high silica content makes them extremely durable, resistant to mould and insects.
• It is a good thermal and sound insulator and fireproof.
• It is a local resource: Rice is grown on 230,000 hectares in Italy, 1.6 million tonnes a year, more than 90% of which is grown in northern Italy, where Ricehouse is located. The rice husk and straw are therefore sourced from local producers in the area between Turin and Milan. In this way, the carbon emissions caused by transportation are not significant.

The housing tower blocks in Milan – An example of insulation with rice by-products were

The Clever Cities project renovated four eight-storey social housing tower blocks in Milan, owned by the Lombardy region.

Before the renovation:

• The façades were originally 12 cm thick; they neither provided protection against the cold in winter, nor against the heat in summer.
• In the project they were insulated with fire-resistant panels of compressed rice straw, covered with ricehusk-based plaster.

After the renovation: the energy efficiency of the buildings has improved dramatically

• Energy consumption decreased from from energy class G to class A4 (A++++) They were upgraded to nearly zero-energy (nZEB). The annual energy demand, originally close to 60,000 kWh/m², has been reduced to less than a tenth, to around 5,000 kWh/m²/year.
• The roofs have also been insulated and roof gardens have been created.
• Solar panels were installed on parts of the roof. This works in combination with the roof garden, as evaporation from the garden cools the air temperature on hot days, which helps to prevent the solar panels from losing power due to the heat.  

The aim was to enable low-income residents to grow healthy, chemical-free fruits and vegetables for their own consumption at low cost. In the long term, however, they want to make the gardens profitable and provide jobs for the people living in the buildings. Rooftop gardens increase biodiversity and reduce the heat island effect, which is common in cities in summer. The implementation of the green roof was financed by the Clever Cities project, but also involved several local stakeholders: universities, public and municipal institutions as well as private companies. 

The project was made possible by Italy’s introduction of a so-called super bonus scheme in 2020 in response to the economic downturn caused by the COVID epidemic.

Participating municipalities seized the opportunity to ask questions, share their views and exchange about best practices following the presentation given in the informal Renovation Lunch. The lunch was attended by participants from eleven EU and non EU-States: the participants were from Romania, Hungary, Germany, Slovakia, Croatia, Estonia, Kosovo, Albania, Lithuania, Spain and Portugal. They asked about the compostability of rice-based building materials and suggested that EU member states should have a lower tax on bio-based insulation materials to increase their uptake. Our next renovation Lunch will be in June 2024. More information will be posted on the SURF-website.