Low-carbon and nature-based building products and their potential applications

While the production and use of low-carbon and nature-based building products have rapidly gained ground in Central Europe, there is still a lack of comprehensive data on the technical properties or carbon footprints of these products in Finland. In 2022, the Nature CO2 project at Tampere University collected information on nature-based building materials, and there are similar ongoing projects at other educational institutions.

Text: Mikael Westermarck, Tampere University, Puuinfo

Read the article in Finnish here.

The environmental impact of construction material production

Because it generates greenhouse gases and waste and uses land and raw materials, the construction sector has significant negative impacts on nature and the climate. Buildings and construction use about 50% of the world’s natural resources and 40% of unrefined energy, and the construction sector is responsible for about 35% of greenhouse gas emissions and 30% of the waste produced globally (Ministry of the Environment).

Now that energy consumption by buildings has decreased thanks to more demanding thermal insulation requirements, the industry is increasingly turning towards the low-carbon manufacture of building products to reduce emissions. While there are plans to recycle and reuse raw materials and building components to make the sector more sustainable, this is not sufficient by itself. Whether the raw materials are recycled or produced by consuming natural resources, the high heat required to produce the most common stone and metal building materials present a challenge. Industry has so far only been able to reach such temperatures using fossil fuels. Hydrogen could be an environmentally friendly option in the future to produce this electricity in a low-carbon manner.

Nature-based building products

Nature-based building (NBB) products are manufactured at low temperatures from renewables and from common nature-based raw materials, offering an interesting alternative for low-carbon construction. These raw materials come directly from the agricultural, forestry, and mining industries and share characteristics with other low-carbon commodities such as bio-based and circular economy products and industrial side streams.

Potential impacts on the greenhouse effect

Wood-framed structures have only about a tenth of the carbon footprint of stone structures. A report produced by the Nature CO2 project found that this carbon footprint can be decreased by an additional 10-15% by replacing the typical mineral wool, gypsum board, and plastic vapour barriers of wooden structures with nature-based building products.

Once carbon recovery methods like producing biochar from demolition waste become pervasive, construction products and structures that contain a lot of organic raw material will even flip from being low-carbon to being carbon-negative (ISO 14067 Article 6.3.8).

Building physics research group explores nature-based construction
The NatureCO2 project
revealed that the production and use of nature-based building products are already accelerating in Central Europe. While these products could also be a realistic option in Finland and other Nordic countries, we still need studies to prove that they suit our northern climate and meet local goals for fire safety and indoor air quality.

Hopefully, this project will lead to the industrial production of nature-based building products in Finland. Further visions include making the use of nature-based building products the prevailing construction method in Finland and turning this expertise into a Finnish export. This will require further basic research on nature-based raw materials and their processing before the industry can leverage modern production technology such as nanotechnology, 3D printing, spraying and foam-based techniques, the modification of natural adhesives and automation.

For more information, see https://research.tuni.fi/rakennusfysiikka/tutkimusprojektit/natureco2/

Ecosafe projects seek to investigate how well chipboard insulation works from a moisture-technical perspective. Earlier research shows that mixing clay into the chips lowers the relative humidity of the exterior wall structure, which reduces the risk of mould developing. In turn, a clay plaster covering improves the fire-resistance of partition walls insulated with chipboard, allowing the structure to withstand fire for more than an hour. Preliminary research in collaboration with Aalto University seems to indicate that clay can help structures recover from microbial damage: good microbes thrive in the clay’s porous structure and convert VOC gases into carbon dioxide. Clay also has the additional benefit of absorbing odours.

For more information, see https://research.tuni.fi/rakennusfysiikka/tutkimusprojektit/ecosafe/

The Stalk project focuses on the use of straw-filled wooden elements in structures over two storeys tall. The aim is to increase positive climate impacts through the construction of multi-storey buildings.

This project has four separate streams:

  • TP1 looks at the moisture and thermal performance of straw elements in northern climates and at what interior and exterior surface solutions work best. 
  • TP2 involves collaborating with the South-Eastern Finland University of Applied Sciences (Xamk) to develop construction panels made from lake reeds with bio-based binders such as starch. These panels could replace the porous fibre board that is currently used in straw structures, with the added bonus of removing nutrients from eutrophic water bodies. 
  • TP3 is searching for the best plastering mixture to protect straw elements from fire, combining clay and sheep’s wool with naturally fire-resistant biochar. Several European projects in addition to Ecosafe have studied the fire protection properties of clay plaster. Still, Finnish fire regulations on buildings with a lot of biomaterials have created a bottleneck in multi-storey construction. In the Stalk project, the fire safety of structures is assessed by simulating a fire according to the P0 procedure. 
  • TP4 is creating a training package based on the materials from the Nature CO2 project and the Stalk project’s sustainable multi-storey building design. This training package will include information on this building system’s technical characteristics, building technology, prices, climate impacts, and indoor air health effects. The presentation material will be used in various training events for the construction industry and will be freely available online. 

The Biosivu project at the South-Eastern Finland University of Applied Sciences (Xamk) is looking for a use for oil hemp reeds and aims to make construction panels similar to lake reed board. Tampere University is also researching the material properties of hemp panel and developing a fire-retardant from clay and shredded hemp reed – in essence, a dry version of clay plastering.

For more information, see https://www.xamk.fi/tutkimus-ja-kehitys/biosivu-oljyhampun-sivuvirroista-tuotteita-vahahiiliseen-rakentamiseen/

Do nature-based products complement wooden structures?

Tampere University’s Nature CO2 project has produced a study that indicates how nature-based building products (NBB products) could be used in Finland to complement wood structures and how they could be combined to create a number of innovative building construction concepts.

Nature-based building products have positive health effects thanks to their breathability, moisture security and non-toxic nature and their ability to eliminate odours and even out room air humidity and temperature. Together, these properties present a strong case for using NBB products.

Available environmental reports also show that NBB products could already reduce the carbon footprint of conventional wooden structures by an estimated 10–15%. However, it should be noted that future investments, production volumes and renewable energy resources will greatly impact the production costs and carbon footprint of NBB products. This makes it difficult to determine how low their eventual prices and carbon footprints will be. Finland is in an excellent position to produce nature-based and low-emission building products because of the steadily increasing amount of wind power capacity and the excellent availability of raw materials. Taken together, these factors would allow us to be self-sufficient in building material production.

The Nature CO2 project also proposes how carbon footprint calculations could take into account the carbon recovery from turning construction waste into biochar. For example, using pyrolysis processes would prevent about half of the carbon stored in structures from returning to the atmosphere. The carbon sink also remains relatively intact when annual plants are used as raw material for building products.

This project has revealed that there is a pressing need for research and development of NBB products. Product development, training, and the general promotion of NBB would be a natural fit for Tampere University’s built environment faculty. For example, external funding would allow the university to set up an innovation centre.

AUTHOR OF THE ARTICLE Mikael Westermarck started researching organic building materials in the early 1990s when he graduated as an architect.