"This also means that we don’t know at all well what the greenhouse-gas implications of construction are, and that they cannot be properly incorporated into greenhouse-gas mitigation policies," Antti Säynäjoki of Aalto University in Finland told environmentalresearchweb. "Our work shows that further development is urgently needed before LCA can provide reliable-enough information in the building sector."

Säynäjoki and colleagues reviewed LCA studies on the pre-use phase of buildings. They examined 116 cases from 47 articles and reports that used process LCA, input–output LCA or hybrid LCA to determine the greenhouse-gas emissions as buildings were constructed. The buildings emitted between 0.03 and 2.00 tons of greenhouse gas per unit of gross area, according to the studies.

"The most significant result is that the methodological issues and subjective choices of LCA practitioners rather than the building characteristics actually explain the major share of differences of results between the different studies," said Säynäjoki. "This is particularly serious when comparing the results of LCA studies conducted with different methods but quite often with similar methods as well."

Säynäjoki stresses that decision-making based on LCA results should always require a decent understanding of the methods used in the studies. "In theory, two LCA practitioners would be able to conduct standard comparative LCAs of two objects and come up with completely opposite results because of the different methods and subjective choices made during the LCA processes," he said. "Accordingly, studies’ conclusions concerning, for example, material choices or significance of different life-cycle phases might be completely opposite as well. Thus, observing just the results without comprehensive knowledge of the underlying assumptions of the studies is likely to lead to poorly reasoned decision making."

Säynäjoki concludes that LCA studies should include more comprehensive reporting "so that the before-mentioned characteristics could be studied in the first place – currently, even experts within the field of LCA are having difficulties in interpreting LCA processes because of the incomplete reporting".

The team discovered that construction-phase emissions of similar buildings varied significantly between LCA studies when they were examining the greenhouse-gas implications of residential development projects.

"We had an assumption that LCA studies are used in decision-making without having a decent understanding of the underlying characteristics that seem to have a great influence on the results," said Säynäjoki. "Thus, we considered it critical to provide high-quality scientific information on the consequences related to non-contextual issues in LCA studies, such as method choice and boundary definitions. Additionally, although the variance in the results of LCA studies has been widely discussed for a long time, there are not many studies related to it. We saw a clear demand for the review study from the perspective of both decision-makers and the academic community."

The scientific community has done great work in developing a wide array of sophisticated LCA methods and tools, Säynäjoki believes. "The multitude of different LCA approaches provides an excellent opportunity of producing scientific knowledge from various perspectives," he said. "Multi-directional and free development of LCA methods also promotes innovation and provides opportunities to add important features to improve the methods’ capabilities of reflecting real-world characteristics, for example from the point of view of carbon sink and concrete carbonization mechanics as well as taking temporal occurrence of greenhouse-gas emissions into consideration."

Now the researchers will continue to study the life-cycle sustainability of the built environment. They are currently comparing the uniformity of the most common LCA databases, as well as looking at how digital solutions can promote sustainability and business opportunities in the real-estate and construction sector. "Opportunities provided by smart buildings are a very interesting field where LCA will without a doubt be an important assessment tool," said Säynäjoki. "Currently, we have an ongoing ‘Internet of Buildings’ research project; the academic article related to it will be published later this year."

The team reported the findings in an Environmental Research Review.

Related links

Related stories