No other building material performs better in life cycle assessments of buildings than wood. The low energy input in production and the high proportion of renewable energy stored via photosynthesis, which can be used energetically when disposing of timber building materials at the end of the longest possible utilisation cascades, lead to an outstanding plus energy balance.
Wood is the best example of sustainable, environmentally friendly material use: in addition to its energy-plus balance, wood as a building material, unlike mineral building materials, is a CO2 reservoir - in the forest as well as in the built state -, photosynthesis produces fresh air as a "waste product" and forests bind large quantities of dust. Furthermore, the use of wood preserves or creates local jobs, as well as recreational and living spaces.
Wood leads to a plus energy balance of buildings when used massively. This can be calculated with the help of life cycle assessment tools and has been proven in numerous life cycle assessment studies. In optimised buildings such as passive or plus-energy houses, up to 2/3 of the total primary energy expenditure can come from the building materials. If the environmental impact is to be further reduced, it is worthwhile to start with the building materials and use materials with a low energy input for production or renewable building materials such as wood with a plus-energy balance.
The adjacent figure shows the comparison of a timber building in board stack construction with a brick and reinforced concrete variant. The complete life cycle was taken into account, from the extraction of the raw materials and their use to the thermal disposal of the timber building materials in a combined heat and power plant or the landfilling of the mineral building materials.
Assuming a useful life of the buildings of 80 years, which is common in LCA studies, significant differences result from the choice of materials for the primary energy demand of the building. At slightly more than 1,000 kWh/inhabitant and year, timber construction is significantly more favourable than mineral construction. This corresponds almost exactly to 27 kWh PEI/m2 NGF*a. Assuming a service life of 50 years for the buildings based on the specifications of the sustainability certification of the German Federal Ministry of Construction and the DGNB, this even corresponds to 43 kWh PEI/m2 NGF*a.
In comparison, the annual heating requirement of a passive house is less than 15 kWh/m²a. This can be supplied with a PEI of 14 to 20 kWh/m2a, depending on the efficiency of a heat pump air heating system. This means that the primary energy savings through the choice of wood as a building material reduce the PEI by almost twice the amount of energy still required by a Passive House. On the basis of the total primary energy demand (PEI) of a passive house with a value of ≤ 120 kWh/(m²a), including all electrical consumers, the PEI of the building materials become relative, but remain in line with the findings of the life cycle assessment studies: the more wood is included in the building, the better the life cycle assessment.
In addition to other renewable raw materials, wood has the advantage that it can be used as both a load-bearing and insulating building material.
The article was first published with the title "Ökobilanz: Punkte mit dem Plusenergiebaustoff Holz" in the proceedings of the International Timber Construction Forum (IHF) 2009, Garmisch Partenkirchen. Long version: www.forum-holzbau.ch/pdf/ihf09_Wolpensinger.pdf
Further details on the calculations can be found in the diploma thesis "Life cycle assessment of settlements“.
by Holger Wolpensinger (chronologically sorted, new above):
Wolpensinger, Holger (2015): "Project conclusion HCE II - Climate protection through wood use - and project start HCE III" Press release HolzCluster.Eifel
Wolpensinger, Holger and Rid, Wolfgang (2010): Nachhaltiger Wohnungsbau: Standards und Innovationen. In: DETAIL 3/2010. Munich (also published in English long version).
Wolpensinger, H. (2010): Energie-Wunder. In: holzbau austria. Trade magazine for Austrian timber construction. 2/2010, Vienna
Wolpensinger, H. (2010): Wood - a building material with many advantages. In: Exhibition newspaper of the "9th Swiss House Building and Energy Fair 2010? p.37. Swiss Federal Office of Energy, Federal Office for the Environment. Basel
Wolpensinger, Holger (2009): Bauen mit Massivholz. In: ZENO - Journal for Sustainable Building, Munich
Wolpensinger, Holger (2009): Energieeffizienz XXL - Nachhaltige Stadtquartiere, Siedlungen und EcoCity-Projekte weltweit. In: Collinet, Hans-Dieter; Pesch, Franz (2009): Stadt und Landschaft - Neue Verhältnisse im urbanen Raum. Herdecke/Stuttgart
Wolpensinger, Holger (2009): Eco-settlements in Germany and Europe. Handout for the DIFU seminar "Energy- and resource-efficient settlement development". Berlin
Wolpensinger, Holger (2009): Der Baustoff Holz aus ökobilanzieller Sicht. Lecture script in: Wallbaum et al. Proceedings of the 3rd International Summer Academy on Sustainable Construction at ETH Zurich.
Wolpensinger, Holger and Rid, Wolfgang (2009): Points with wood as an energy-plus building material. In: Zukunft Holz - Statusbericht zum aktuellen Stand der Verwendung von Holz und Holzprodukten im Bauwesen und Evaluierung künftiger Entwicklungspotenziale. Stuttgart
Wolpensinger, Holger (2009): Life cycle assessment: Wood is ahead. In: mikado 5/2009
Dederich, Ludger and Wolpensinger, Holger (2009): Schlicht Nachhaltig: Bauen Mit Holz. In: BDA Yearbook 2009. Berlin
Wolpensinger, Holger (2009): Plusenergiebaustoff Holz. In: DW Die Wohnungswirtschaft special issue GREEN BUILDING. Hammonia-Verlag Hamburg March 2009
Wolpensinger, Holger (2006): Nachhaltigere Siedlungen mit Hilfe von Ökobilanzen. In: Genske, Dieter, Huch, Monika and Müller, Bernhard (2006): Fläche-Zukunft-Raum: Strategien und Instrumente für Regionen im Umbruch. Hanover: German Society for Geosciences, Short description of the book (pdf 230 kB).
Hertle, Hans; Kolbe, Peter and Wolpensinger, Holger (2003): CO2-Bilanz 2001 Kronsberg. Study commissioned by the City of Hannover. Heidelberg partial publications: CO2-Bilanz 2001 und Zusammenfassung bzw. in English: CO2 Audit Hannover Kronsberg Commissioned by the City of Hannover Environment and Urban Greenspace Environmental Protection Division.
Wolpensinger, Holger (2003): Ökobilanzierung von Siedlungen. In: Ökologie im Wohnungs- und Siedlungsbau. Housing Association Information, Munich
Wolpensinger, Holger (2002): Ökobilanzierung von Siedlungen unter Berücksichtigung von Lebensstilaspekten. Diploma thesis at ifib - Institute for Industrial Building Planning University of Karlsruhe.
Wolpensinger, Holger (2001): Ökobilanzierung im Wohnungs- und Siedlungsbau. Student research project. Karlsruhe
Sources (chronologically descending)
FNR Portal (2015): https://mediathek.fnr.de/broschuren/nachwachsende-rohstoffe/bauen.html
Thünen-Report 9 (2013): Holzverwendung im Bauwesen - Eine Marktstudie im Rahmen der "Charta für Holz". Braunschweig
Schmidt, Marco (2009): Global climate change: the wrong parameter. Proceeding of the conference "RIO 9 - World Climate & Energy Event. Rio de Janeiro
Feist, Wolfgang (2008): Life cycle assessment of building concepts. In: Proceedings of the 14th International Timber Construction Forum (IHF 2008). Biel
Architects Waugh Thistleton (2008): Townhouse. Press Release from 30.5.2008
BMBF (2008): Joint project: ÖkoPot - Ökologische Potenziale durch Holznutzung gezielt fördern. Final report. Bonn
Wegener, Gerd (2008): Zukunftsaspekte des Bauens mit Holz. In: Proceedings of the 14th International Timber Construction Forum (IHF 2008). Biel
Renner, Alexander (2007): Energie- und Ökoeffizienz von Wohngebäuden. Development of a procedure for life-cycle oriented assessment of environmental impacts with special consideration of the use phase. Diss. Darmstadt
Ekkerlein, Christian (2004): Ökologische Bilanzierung von Gebäuden in frühen Planungsphasen auf Basis der Produktmodellierung. Diss. TU Munich.
Streck, Stefanie (2004): Entwicklung eines Bewertungssystems für die ökonomische und ökologische Erneuerung von Wohnungsbeständen. Diss. University of Wuppertal
Oswald, Gudrun (2003): Ökologische Bewertung im Holzwohnbau. Diss. University of Graz
Federal Environment Agency (2003): Sustainable Building and Housing in Germany. Material flow-related building blocks for a national concept of sustainable development - linking the field of building and housing with the complementary field of "public infrastructure." Bonn/Berlin
Adriaans, Richard et al. (2002): Das AktivHaus. The house with the better energy balance. Working Group for Ecological Timber Construction, Herford
Getto, Petra (2002): Entwicklung eines Bewertungssystems für ökonomischen und ökologischen Wohnungs- und Bürogebäudeneubau. Diss. University of Wuppertal
Frühwald, Arno et al. (2001): Holz - Rohstoff der Zukunft. Sustainably available and environmentally sound. Hamburg
Wegener, Gerd; Zimmer, Bernhard (2001): Holz und seine Bedeutung als zukunftsfähiger Rohstoff, Energieträger und Kohlenstoffspeicher. In. The German Forest. Ed.: LpB
Wegener, Gerd et al. (1997): Ökobilanzen Holz. Reading, understanding and acting on facts. Munich
