What’s needed are innovative ways to make the construction process less carbon intensive, more efficient and more sustainable, and to make the resulting buildings more energy efficient, healthier for their occupants and reduce their environmental impacts. At Skanska, we have long worked to foresee global trends, to care for people and to protect the planet. Below are four of the construction innovations that we are investigating, developing and or are actively involved in as a way of reducing the environmental impact of construction and the built environment.
Concrete is a versatile material to build with, but production of the cement needed for concrete mixes is very carbon intensive. Low-carbon concrete is made by replacing a portion of the cement in the mix with alternative, less carbon-intensive binding ingredients, such as fly ash (a waste product from coal power stations) and slag (a waste product from conventional steel production). When the proportions are correct, the result is a less carbon-intensive product whose strength is equal or near-equal to conventional concrete.
At Skanska, we have developed and launched a range of concrete mixes with 40 to 50 percent less carbon than traditional mixes. As part of our commitment to circularity – considering the entire life cycle of materials – we are also pioneering the use of recycled concrete as aggregate in concrete mixes, something which also reduce waste.
Prior to the modern rediscovery of concrete, wood was the most common material for building structural elements in larger buildings. And with the world now looking for low-carbon options, it is again growing in popularity. ‘Mass timber’ consists of multiple solid wood panels nailed, dowelled or glued together to create elements that can bear loads and be incorporated into a structure. Far less CO2 is produced during mass timber’s production compared with concrete, providing environmental benefits. It also has excellent potential from a circularity perspective, as it can be removed and reused when a building’s lifespan comes to an end.
We have successfully used mass timber in several multi-story structures, including in the Växjö town hall and train station in southern Sweden. Standing seven stories tall, the building features supports, beams and ceilings made of mass timber. Mass timber was also used in the timber frames on the lowest and top floors.
Fossil-free construction sites
While concrete is the largest contributor to carbon emissions on most construction sites, emissions from fossil-fuel powered vehicles make an impact too. Fossil-free sites are those where all the machines associated with the site are powered by electricity or alternative fuels. This includes machines used for material transport to and from the site, and for excavation, materials handling and construction. We are currently, in cooperation with Volvo Construction Equipment, operating Sweden’s largest fossil-free site in Stockholm as we carry out enabling works for the Slakthusområdet redevelopment for the City of Stockholm. The redevelopment of the old meatpacking district is being undertaken with machines that run on both electricity and hydrotreated vegetable oil (HVO). Our individual team members are also encouraged to travel to site by bicycle or public transport
Traditional buildings require considerable external inputs of energy both during their construction phase and then throughout their lifetimes. The energy consumed is often produced by non-renewable sources that produce significant emissions. ‘Energy-positive buildings’ turn this equation on its head. Through the use of renewable energy solutions and sustainable construction practices, such buildings produce more energy across their lifetimes than they consume during construction and operation. As such, they have the potential to significantly reduce carbon emissions.
At Skanska, we are helping pioneer this approach, through the Powerhouse concept. Working collaboratively with partners like architectural firm Snøhetta, we have now created four Powerhouse buildings across Norway, including office buildings and a school, and are currently working on student housing and a residential development.
The Sweden Green Building Council has developed a certification (NollCO2) for buildings that are able, over a period of 50 years, to compensate for emissions related to the construction phase. By using solutions including solar panels, fossil-free machines, climate improved concrete, recycled reinforcements and glass, the Hyllie Terrass development in Malmö is our first office building certified under NollCO2.