The building sector is responsible for around 40 percent of greenhouse gas emissions in Germany. Across Europe, 65 percent of all cement, a third of steel, a quarter of aluminum and a fifth of plastics go into building houses. It’s not sustainable.
From a cost-benefit point of view, the first and most effective improvement measure is inventory optimization: improving the energy efficiency of old buildings, using residential and commercial space more efficiently, conversion and conversion instead of demolition and new construction.
The new building, which is still necessary, is to be consistently geared towards inner-city building, away from the green field. With the efficient use of existing infrastructure and developed building plots, considerable amounts of material and energy can be saved.
The second lever is the trend towards building with renewable raw materials such as straw, hemp and, of course, wood. These materials have a good eco-balance and many advantages in terms of building physics. They are available domestically in sufficient quantities and have an ecologically important property: they bind CO2.
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With a small part of the annual wood harvest in Germany, the entire need for new construction could be met. Understandably, the solid construction industry wants nothing to do with this. What is annoying, however, is that the currently common construction methods characterize the building regulations. Sustainable construction methods, even well-tried ones, are disadvantaged.
The life cycle of buildings must be assessed in a more differentiated manner
A little-noticed obstacle is hidden in the life cycle analysis of buildings. The material and energy flows from the extraction of raw materials through the construction and use phase to demolition and disposal are balanced. State subsidy programs and procurement guidelines as well as the sustainability ratings for real estate are based on the results.
Ulrich Kriese is spokesman for construction and settlement policy for the Nature Conservation Union (Nabu) and co-founder of the reform initiative “Property Tax: Contemporary!”.
For consumer goods, for which this approach was developed, it makes sense because it focuses on the often significant environmental impact of a product before and after the mostly relatively short usage phase. In the case of building with wood and other renewable raw materials, however, this logic leads to the wrong result: according to the assumption that the material is ultimately burned or rots, the carbon dioxide stored in the wood is released again.
As far as the ecological balance is concerned, this results in a zero-sum game, i.e. no justification for preferring this type of construction in the allocation of subsidies, in public contracts or in private investments. However, the very long period of time in which the CO2 remains bound in the building is not taken into account.
A building erected today will probably last for a hundred or more years – think of centuries-old half-timbered houses made of wood, straw and clay that are still intact today. A way to quickly bind CO2 on a large scale for a hundred years is ecologically very valuable.
It is also likely to become increasingly standard to install wooden beams, boards and floorboards from the outset in such a way that they can later be easily removed and reused.
In the majority of cases, the release of greenhouse gases is therefore likely to be in the distant future. However, Germany would like to become climate-neutral by 2045 – i.e. within a single building renovation cycle. Building with wood and other renewable raw materials could play a key role if its contribution to climate protection were recognized by regulation.
More: From single-family homes to high-rise office buildings: Why wood is the material of the moment as a building material