How can a Climate-Neutral Building Look Like?

The climate crisis is urging us to act fast. Buildings are a key leverage point to reduce greenhouse gas (GHG) emissions, but the embodied emissions related with their construction remain often the hidden challenge of any ambitious policy. Considering that a complete material substitution is not possible, we explore in this paper a material GHG compensation where fast-growing bio-based insulation materials are used to compensate building elements that necessarily release GHG. Looking for analogies with other human activities, different material diets as well as different building typologies are modelled to assess the consequences in term of bio-based insulation requirement to reach climate-neutrality. The material diets are defined according to the gradual use of herbaceous materials, from the insulation up to the structural level: omnivorous, vegetarian and vegan. Our results show the relationship in terms of volume between the climate intensive materials and the climate-negative ones needed to neutralize the overall building GHG emissions. Moreover, they suggest how climate-neutral building can look like and that it is possible to have climate-neutral buildings with wall thickness within the range of current construction practices.

Substitution impacts of wood use at the market level: A systematic review

Background: There is strong evidence that wood-based products are typically associated with lower fossil-based emissions over their lifecycle than functionally equivalent products made from other materials. However, the potential impact of large-scale material substitution at the market level remains challenging to quantify and is subject to assumptions and system boundary considerations. Methods: This paper presents a systematic review covering 44 peer-reviewed studies that quantify the substitution impacts of wood use at the level of a region or sector, to assess the commonalities and differences in scopes, system boundaries and key assumptions. We estimated the average and range of market-level substitution impacts and identify the caveats and knowledge gaps for such assessments. Review results: The results indicate an average substitution factor of 0.55 tonnes of fossil C avoided per tonne of C contained in wood harvested, with a range of 0.27 to 1.16 tC/tC for baseline scenarios covering all wood flows. This value depicts the average efficiency of avoided fossil emissions per unit of wood used for a certain wood use structure based on published studies but is of limited practical use as it is strictly context specific. A direct comparison between studies is complicated because a notable proportion of the studies provided insufficient information to estimate substitution factors or were not transparent in their assumptions, such as specifying which wood product is assumed to substitute for which non-wood product. Discussion: A growing number of studies focus on policy-relevant analyses of the climate change mitigation potential associated with marginal changes in wood use, but market dynamics are generally considered to a limited extent. To further support decision-making, future studies could focus on changes in those end uses where increased substitution impacts could realistically be expected, while considering the various market dynamics and uncertainties.

Substitution of Building Components in Historic Buildings

Historic buildings that have survived to the present day have been subject to maintenance, repair, and overhaul. Repair work is being carried out so that it can be enjoyed by future generations. However, there have been changes in the construction technology: some construction products have been discontinued and replaced with others of different quality parameters, lower prices, etc. It is necessary to use substitute products during construction work—that is, replacement products that are shaped after the original. Therefore, there is a problem of selecting the best possible substitute material, taking into account many important factors, including the recommendations and requirements of the conservator. This paper presents a methodology for the process of material substitution planning and selection of a substitute with the use of multicriteria analysis, by implementing it in the refurbishment of a historic building façade.