Mr. Schoch, what are the reasons why in the public discussion when comparing timber and concrete construction methods, often only the raw material itself is compared?
From my point of view, it is mainly about simplifying the discussion and thus giving the impression, also politically intended, that I am doing something good for the environment with timber construction. According to the calculation: every cubic meter of wood avoids one cubic meter of mineral building material with a CO2 footprint. This is easy to convey, but it is wrong.
Because everything what happens in the remaining 50 to 80 years in the life cycle of a house is ignored: The construction itself, maintenance, operation, dismantling and reuse. In public this is often not talked about. Yet it is enormously important to compare the footprint of the entire life cycle. Together with the experts from Darmstadt, we have calculated this for a classic single-family house made of autoclaved aerated concrete and a timber-frame house.
Let's go through the different phases. What happens in the first phase?
Up to the construction phase, wood absorbs CO2 in the forest, while the mineral building materials such as autoclaved aerated concrete, but also calcium silicate units or brick and concrete consume CO2. But it is not that simple. Wood is also processed, the gypsum board that is necessary in timber construction is not produced in a CO2-neutral way, and even a timber house is not set in the sand but on a concrete floor flat.
For our consideration of a life cycle of 50 years, we arrive at 70 to 80 tons of CO2 for a house made of autoclaved aerated concrete and at approx. 20 and 30 tons of CO2 for a house built according to the timber construction method. We start the construction phase with this difference. In the construction phase the balances do not differ much, the CO2 emissions are about the same.