Quantifying the costs and reduction potential of mass timber

Abstract

The building and construction sector was in 2018 responsible for 39% of the global CO2 emissions. Majority of this 39% is linked to the operational energy usage of buildings. As a result of shifting towards buildings with better energy performance, the environmental impact due to construction materials is becoming more relevant. Mass timber, a biobased alternative for high energy intensity materials such as steel and reinforced concrete, can significantly reduce construction material related impacts. Although mass timber is increasing in popularity, a massive switch to mass timber constructions in the Dutch built environment is not witnessed despite the significant demand for new buildings. Studies quantifying the expected costs and environmental impact reduction of mass timber remain scarce but can aid in making mass timber more accessible for construction companies. This study combines a LCA, LCC and scenario analysis to quantify the costs related to reducing environmental impacts and specifically GWP by constructing a mass timber case house instead of a reference traditional house. Via the EN 15804 LCA framework, the mass timber case house proves to reduce the total environmental score related to 11 impact categories, with 27% compared to a reference traditional case house. The GWP specifically was reduced with 66%. CO2-eq mitigation significantly increases when delay in emissions via temporary biogenic carbon storage is taken into consideration via a DLCA. The mass timber case house has a net negative GWP over a 100 year timespan and emits 108% less CO2-eq per m2GFA compared to the reference house. The global warming reduction potential of the mass timber case house goes accompanied by an increase in construction costs of 35%. The higher costs are caused mainly by the LVL frame, which is 88% more expensive than the reinforced concrete frame of the reference house. When taking discounted O&M costs and demolition costs into account, the LCC of the mass timber house is 13% higher compared to the traditional reference house. Assuming a scenario in which all 267 thousand Dutch terraced houses built in 2020-2030 are constructed in mass timber and a carbon tax would be applied, 710 Kton CO2 can be mitigated against 10% higher LCC costs. This reduction would attribute and additional 0,11% to reducing annual emissions in order to reach the Dutch 2030 climate goal.