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Recycling, reuse, and extending service life within reasonable limits are the core ideas of sustainability. Of course, buildings also fall within this. The preservation and remodeling of a home is preferable to its demolition in order to create way for a new structure that is more energy-efficient. Sustainable building materials have a vital role in energy and resource efficiency as well as a sustained rise in the value of modified existing buildings.

from hicklvesting.

What is needed, writes the Baukultur Foundation in its building culture report 2022/23, is a smart culture of conversion that uses the gray energy or rather the gray emissions of existing buildings and considers the environmental impact of the materials used when continuing to build. The building sector can only achieve sustainability in this way in order to meet goals for climate and environmental protection.

The conversion and renovation of residential buildings will make up almost two thirds of all construction activities in Germany in 2020. This may appear to be a lot at first glance, but demolition and new construction are still too often the ostensibly apparent solution when dealing with buildings whose design and floor plan do not appear to satisfy contemporary standards, market conditions, or efficient, economical use. The values, materials, and gray energy that have been part of the buildings since they were built frequently become lost in the background. This profound energy is appropriately called “golden energy” by the Foundation Baukultur.

Consequently, constructing sustainably entails concentrating on what currently exists and has long fulfilled our needs. The advancement of the building fabric is essential to the future of construction. It provides architectural and ecological potential for renovation and new building that is still far from being used up. By maintaining the existing structure with care, we not only increase its lifespan but also safeguard the community’s unique identity and ensure that history is being written in a way that is accurate.

Sustainable compaction

In order to expand in width and avoid adding more buildings to meet the growing demand for housing in densely populated cities, it is required to plumb heights, reuse spaces, and utilize unused regions. Additionally, this must be completed swiftly, with the least amount of disruption possible—basically within continuing operations—and thoroughly utilizing sustainable raw materials. Natural materials consistently insulate against cold and heat, improve the indoor temperature, and boost living comfort. Space is created by light, flexible wood constructions. A restored building’s life cycle is extended and adjustments to the structure are not required for a considerable amount of time when they are planned ahead of time and carried out to a high standard. Therefore, a major factor in both a sustained growth in the value of updated existing buildings and the necessary energy and resource efficiency in the construction sector is the use of sustainable building materials made from renewable raw resources.

Building with sustainable building materials to conserve resources

Which renewable raw material-based sustainable building materials are currently especially well-suited for construction inside of existing structures? That absolutely relies on the building component in question. Basically, the materials and construction of newer buildings today and those that are already in existence vary. They were constructed using tools and methods that are sometimes no longer used in contemporary architecture. The majority of locally accessible sustainable building materials were of mineral and vegetative origin. These include brick, lime, wood, straw, and thatch in addition to natural stone and clay. These materials offer excellent biological building qualities. They are mostly pollution-free, open to diffusion, take in moisture from the environment and release it again as needed, and they do not develop electrostatic charges.

The “livMats Pavilion” in the University of Freiburg’s Botanical Garden serves as an example of a resource-effective, sustainable replacement for traditional construction techniques. It is the first structure whose entire load-bearing structure is built of robotically woven flax fibers, a locally accessible, natural, renewable, and biodegradable material. It is a collaboration between interdisciplinary teams of biologists from the Cluster of Excellence “Living, Adaptive and Energy-autonomous Material Systems (livMatS)” at the University of Freiburg and architects and engineers from the master’s program ITECH at the Cluster of Excellence “Integrative Computational Design and Construction for Architecture (IntCDC)” at the University of Stuttgart.

The short transport distances of the region’s natural and renewable raw materials continue to be advantageous. Another option to construct with less waste is to use pre-owned building materials, which are recycled once another building is demolished rather than being dumped. They can be recycled right there, cutting off the need for transport routes, which is known as “urban mining.” The less complicated the better because composite materials are harder to separate and recycle, making them ideal for use in construction within existing structures. Certified sustainable building materials can be selected with the aid of recognized construction labels.

Continue building with the all-rounder wood

When it comes to densifying cities, accurate, low-disturbance, cheap, and time-saving construction methods are in high demand. Construction using timber, particularly prefabricated and elemental timber construction, is particularly ideal for constructing in already-existing structures and is especially suitable for limited urban building conditions. Building projects can be implemented substantially regardless of the season with a high degree of precise planning throughout the whole construction process. However, regional factors and transportation options also affect the component sizes. In exchange, the construction site may be built up quite rapidly. When gaps between buildings need to be filled in or buildings need to be expanded, a quick construction process using prefabricated building components lessens the disruption to the densely populated surroundings.

Lightweight timber elements can be incorporated into the existing spatial structure for the conversion of previous production and office buildings, achieving new functions. Cross-laminated timber or hollow box elements used across a large area strengthen the top floor slab and pass the additional loads to the existing wall structure if static reserves of the existing load-bearing structure are insufficient for an addition, as is frequently the case with residential buildings from the 1950s and 1960s. Open areas and unrestricted floor plan design are made possible by wall components in timber frame construction or as cross laminated timber panels.

Insulate sustainably and effectively

The focus is on environmentally friendly construction materials that can be produced as climate neutrally as possible and have a decent insulating effect in comparison to traditional building materials when it comes to thermal insulation materials. Wood, cork, and reed have a long history of success. Straw, hemp, flax, wool, and grass have also been added in the meantime. These insulating materials typically require much less energy to create than glass, rock wool, or polystyrene.

It is possible to get insulation boards composed of wood fiber or mineral foam as an alternative to ETICS systems with polystyrene. Special wood fiber-based boards can be plastered and have an excellent insulating effect. Despite being thicker than polystyrene, they process just as well. Soft wood fiber boards work well as insulating materials in wood construction because they add enough mass, compensate for climate changes, and reduce noise. It is possible to purchase the entire insulating system, including plaster and adhesive, as a natureplus-certified product.  

If demand rises, natural insulating materials can be obtained here in the future mostly from domestic agriculture and forestry. It also opens up new potential for rural areas to serve as manufacturing sites and habitable settings, as well as shorter distances and more independence from imports.


fnr Fachagentur für Nachwachsende Rohstoffe e.V.

Stiftung Baukultur: Baukulturbericht 2022/23 “Neue Umbaukultur”

Kaufmann, Hermann; Nerdinger, Winfried (Hrsg.): Neues Bauen im Bestand, in: Bauen mit Holz. Wege in die Zukunft, München 2016.

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