The role of timber in climate protection
02.08.2023
The study "Ecological Indicators for Investors: Comparison of Timber Construction - Solid Construction" shows a clear result: timber buildings perform better than solid buildings with regard to the implementation of climate protection targets and net zero.
Wüest Partner is developing a platform for investors in collaboration with Lignum and with support from the FOEN. The recently published study "Ecological Indicators for Investors: Comparison of Timber Construction - Solid Construction" by durable Planung und Beratung GmbH lays the foundation for the quantitative comparability of timber buildings with other properties. With the study "Timber construction key figures for investors" from 2020 by Wüest Partner AG, cost parameters for timber construction were determined on the basis of eight realised timber construction projects.
Ecological key figures for investors: comparison of timber construction and solid construction
In comparisons of variants with ten case studies, timber construction projects are compared with their mineral twins. The focus of the considerations is on grey greenhouse gas emissions and the associated biogenic carbon, both of which are essential parameters for the implementation of climate protection goals and for achieving net zero. The timber construction method leads to better results than the respective mineral twin, both when considering buildings and at the level of individual components.
Greenhouse gas emissions at building level
Greenhouse gas emissions at the building level are related to the square metre of energy reference area (EPI). The comparisons of the case studies show that the characteristic values of the mineral twins are between 12% and 41% higher than the respective timber construction method. You can find the entire study here (only in German).
Deviation of mineral twins compared to timber construction in % at building level (timber construction = 0%). Source: Durable Planung und Beratung GmbH
Timber buildings are CO₂ reservoirs
In addition to the lower greenhouse emissions that timber buildings have compared to solid buildings, they store carbon in the long term. During tree growth, photosynthesis removes biogenic carbon from the atmosphere and stores it in the wood. This is only emitted again during decomposition or energy recovery. The KBOB list of life cycle assessment data in the construction sector, version 2022, lists this parameter for each material for the first time.
Can the biogenic carbon content be included in a greenhouse gas emissions balance? No, according to the current status, the biogenic carbon content cannot be taken into account in a balance of grey greenhouse gas emissions. From a climate perspective, greenhouse gas emissions and biogenic carbon are two different effects that cannot be combined into one figure.
For short-term considerations of compensation measures in the coming years, however, it is conceivable that the balanced greenhouse gas emissions are at least compared with the biogenic carbon content in the form of emitted CO₂ emissions.
Rule of thumb: 1m³ of wood stores 1 tonne of CO₂.
According to KBOB list life cycle assessment data, one kilogram of spruce wood contains 0.451 kg of biogenic carbon. With a gross density of 485 kg/m3 , this makes 1075 kg of biogenic carbon per cubic metre of wood. As a rule of thumb, each cubic metre of wood stores one tonne of CO₂. In return, the production of one cubic metre of concrete causes half a tonne of CO₂.
KBOB list Life cycle assessment data: Life cycle assessment data are based on material and energy flows, which are evaluated in terms of their environmental relevance. The life cycle assessment of a building can be determined to a large extent using this data.
Timber construction key figures for investors
Regardless of whether private individuals build single-family homes or institutional investors act as developers in large-scale projects - the costs of construction projects are central. For a long time, there was a rumour that timber buildings are generally more expensive than solid buildings. The study Holzbaukennzahlen für Investoren Timber Construction Indicators for Investors by the consulting firm Wüst Partner AG and the recently published Lignum magazine Was kostet ein Holzbau What does a timber building cost dispels this misconception. The sample and the study focus are still too small to clarify all the details, but one basic statement can already be made: Timber buildings and comparable solid buildings are equally expensive. At the same time, the study shows important advantages of timber construction.
