Exploring the climate impact effects of increased use of bio-based materials in buildings

Abstract

Whenever Life Cycle Assessment (LCA) is used to assess the climate impact of buildings, those with high content of biobased materials result with the lowest impact.Traditional approaches to LCA fail to capture aspects such as biogenic carbon exchanges, their timing and the effects from carbon storage. This paper explores a prospective increase of biobased materials in Swedish buildings, using traditional and dynamic LCA to assess the climate impact effects of this increase. Three alternative designs are analysed; one without biobased material content, a CLT building and an alternative timber design with "increased bio". Different scenario setups explore the sensitivity to key assumptions such as the building's service life, end-of-life scenario, setting of forest sequestration before (growth) or after (regrowth) harvesting and time horizon of the dynamic LCA. Results show that increasing the biobased material content in a building reduces its climate impact when biogenic sequestration and emissions are accounted for using traditional or dynamic LCA in all the scenarios explored. The extent of these reductions is significantly sensitive to the endof-life scenario assumed, the timing of the forest growth or regrowth and the time horizon of the integrated global warming impact in a dynamic LCA. A time horizon longer than one hundred years is necessary if biogenic flows from forest carbon sequestration and the building's life cycle are accounted for. Further climate impact reductions can be obtained by keeping the biogenic carbon dioxide stored after end-of-life or by extending the building's service life, but the time horizon and impact allocation among different life cycles must be properly addressed.

Requirements set by Swedish municipalities to promote construction with low climate change impact

“…One such example is mandatory use of timber frames. Although substituting timber for concrete is usually beneficial in terms of climate change impact (Peñaloza, Erlandsson, & Falk, 2016;Salazar & Meil, 2009), concrete could conceivably be a better solution in cases where it is produced with a low clinker content or carbon storage techniques (De Schepper, Van den Heede, Van Driessche, & De Belie, 2014;Razi, Razak, & Khalid, 2016). On the other hand, performance requirements allow for flexibility and innovation and ensure that the desired outcome is reached, but their implementation and monitoring often require dedicated software, staff training or third party experts.…”

More Timber in Construction: Unanswered Questions and Future Challenges

“…In an assessment of functionally equivalent concrete and timber designs for a small road bridge in Sweden, the timber bridge had a 22% lower EC [23]. Taking a similar approach to residential buildings, a cradle-to-grave LCA result for a CLT-based home had 42% lower EC than its concrete counterpart [24]. In both studies, the superiority of the timber variant was confirmed within parallel assessments using dynamic LCA.…”

A Comparative Study of the Environmental Impact from Transportation of Prefabricated Building Elements Using Wood or Concrete

“…as a fast and cost-efficient building methodology [13], [14]. Wood is one of the most durable construction materials based on its renewability, ability to bind CO2 and requires a limited amount of energy during processing [5]. Further, wood has a relatively low density in comparison with concrete or steel, which allows for the transport of larger volumes, which is beneficial for industrial construction and the environment due to the reduced transport requirement [15].…”

“…Building houses in renewable materials such as wood is beneficial from an environmental perspective. However, Life Cycle Analysis (LCA) analyses are not normally used in the industry, disregarding the positive effects of wood as a construction material [5]. However, wooden multi-family houses are being built to a greater extent than previously due to the support of new technologies.…”