G-38 (Buildings) / G-36 (Products) Sensitivity analysis

Aspect G-38 (Buildings) / G-36 (Products) Sensitivity analysis
Description
According to the ILCD Handbook, the goal of a sensitivity analysis is to assess the reliability of the study by adjusting the main parameters to see how this affects the final results. It is part of the interpretation step, and is generally used together with complementary approaches, such as scenario or uncertainty analyses. Sensitivity analysis can be an effective way of predicting the outcome and the impact of a variable on the result. By conducting it, it is possible to make statements with regard to data quality and precision.Within this guidance document, is a sensitivity analysis necessary? How and when can it be conducted, depending on the study type

related study objective

stand-alone LCA comparative assertion

related study phase

goal and scope definition inventory analysis (LCI) impact assessment (LCIA) interpretation reporting

relevant for

new buildings existing buildings building products screening LCA simplified LCA complete LCA
Provisions A sensitivity analysis should be conducted for LCA studies that include comparative assertions. It may be used for a stand-alone LCA (if relevant to the goal and scope of the study).
Rules from:
EN 15978:
10.3 Data quality
The significance of the data chosen for the building LCA shall be assessed by means of sensitivity analysis (more information in section 10.3 Data quality of the standard)

ILCD:
Provisions: 9.3.3 Sensitivity check (of accuracy and precision)
ILCD states that “it is useful to structure the sensitivity check along the LCA stages.” The sensitivity of results should be checked in order to improve the quality and the validity of the study. The main goals are:

– sensitivity to significant issues (e.g. LCI flows, LCIA factors, modelling choices and assumptions);

– improvement of robustness of sensitive issues data, parameters, methodological choices;

– report final achievements; potentially revise the goal and scope.

Guidance
Sensitivity analysis can be considered as an alternative method for assessing the uncertainty in comparative assertions. It is very similar to scenario analysis, as the main focus is to set a range of variation for a given number of parameters of the LCA study.Sensitivity analysis can be conducted for a stand-alone LCA to assess the range of variation of the LCA results. More frequently, it is used to improve the robustness of decision-making. In comparative LCA studies it enables the user to assess whether alternative X remains better than alternative Y when subject to a modification of the LCA modelling parameters or methodological choices (e.g. burden allocated or not to a by-product).The different aspects to consider for the sensitivity analyses depend on the goal and scope of the study.

1) Guidance for building LCA studies

For example, the usual parameters for building LCA, such as the reference study period of the building (RSP), the end-of-life (EoL) scenarios, the transportation distances, the choice of data for building products, energy and water processes (generic, specific) can be submitted to a sensitivity analysis (if relevant to the goal and scope of the study, and if the LCA tool allows such an analysis). For more information about sensitivity analysis guidelines for building LCA, please consult the LoRe-LCA report ‘Methods and guidelines for sensitivity analysis, including results for analysis on case studies’, available online.

2) Guidance for product LCA studies

For product LCA, the sensitivity analysis can be conducted for the choice of data (e.g. generic vs. specific data for the foreground system), the EoL scenarios, the transportation distances for the upstream processes (e.g. raw materials supply) etc.


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