Emission Reduction Potential of Massive Wood

A massive wood frame solution enables significant reductions in buildings’ life cycle emissions

Part of the collaboration development work was to calculate the carbon footprint for a typical Finnish office building with a concrete-steel frame, and compare that to a massive wood and low carbon concrete framed office design. In addition to the office building, the carbon footprint was also calculated for a typical Finnish residential building with different alternative building frame options. The first option was a concrete element framed building, based on an actual building project located in Espoo. Furthermore, a carbon footprint was calculated for two alternative wood framed building designs. The first one was a wooden conversion design of the concrete frame and the second a design optimized for wood from the beginning. The plot, goals and scope were the same in all of the calculations.

Full report of the emission calculations on the residential building can be downloaded here

Full report of the emission calculations on the office building can be downloaded here

The aim of the carbon footprint calculations was to gain knowledge of the emissions of different frame options. In this collaboration the building was not holistically optimized towards low carbon, instead the focus was on developing optimal low carbon frame solutions. Read more about the background of the buildings from here.

The calculations have been conducted according to the Method for the Whole Life Carbon Assessment of Building by Ministry of the Environment (version: 2021). Read more about the method here.

Main findings of the emission calculations:

Office Building

The whole life carbon emissions of the wooden office building are 15% smaller compared to the concrete building due to the use of low carbon materials.
Looking at the pre-use phase emissions alone, the carbon footprint of the wooden office building is 27% lower than that of the concrete building.
The design solution uses wood, low-carbon steel beams on the first floors, low-carbon concrete and concrete screed from low-carbon concrete products. The strengthening core in the middle of the building with elevators, stairs and rest rooms is made of low carbon concrete.

The greatest product-related reduction of carbon footprint is achieved by the use of low-carbon steel beams and glulam beams, which reduces emissions by 66% from those of the concrete-structured office beams.
The carbon footprint can also be considerably reduced by replacing hollow-core intermediate floor beams with CLT-structured floors, which brings a 55% emission reduction.

Residential Building

The whole life carbon emissions of the wooden residential conversion building are 16% lower compared to the concrete building, while the optimized wooden building obtains 21% lower emissions than the concrete building
The carbon footprint of the wooden conversion building has been reduced compared to the concrete building by using massive wood as the main material
By optimizing the design based on wood's properties, an additional 5 percentage point reduction can be achieved compared to the wooden conversion building
Looking at the pre-use phase emissions alone, the carbon footprint of the wooden conversion building is 24% and the optimized massive wood building 34% lower compared to the pre-use phase emissions of the concrete building

The carbon footprint of an optimized wood-structured residential building is considerably lower than that of a similar concrete-structured building. Replacing the hollow-core intermediate floor slabs with CLT-structured floors brings a 70% emission reduction.
The second largest product-related emission reduction is achieved using CLT-structured walls which allow lowering emissions by 71% from those of concrete-structured load-bearing walls.

Conclusions from the emission calculations

The results prove that wooden frame solutions have a significant impact on the building’s carbon footprint, reducing the embodied emissions up to 34%
The greatest product-related emission reduction can be achieved by replacing hollow core slabs with CLT intermediate floors leading to 70% lower emissions within the product category
In addition to lower emissions, massive wood solutions store carbon throughout a building’s lifespan increasing the carbon handprint of the buildings
Early-phase value chain wide collaboration enables optimization of the design, which can lead to better low carbon solutions and lower emissions