G-26 Use of building physical description data

Aspect  G-26 Use of building physical description data
Description
The type, the format, the level of detail and the quality of building-related data depend on the time of assessment (e.g. concept stage, basic design stage, detailed design stage, as built), on the objective of the study, and on the building’s stakeholders. Which kind of data should be used for a building LCA study?

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 The data for describing the main building elements should be taken from the building’s project documentation already available at the time of the assessment; otherwise use specific documentation included in the LCA software for buildings (if relevant). Different building-related data may be used in the documentation, depending on the objective of the study and the time of the assessment. For example, for screening LCA, an average description of a building could be sufficient, whereas for complete LCA a specific and detailed description of the building should be used wherever possible. Once the building-related data are quantified, they should be associated with suitable LCA or EPD data (see aspect ‘LCA datasets’).
Rules from:
EN 15978

7.5.2 Description of the physical characteristics of the building
9.4 Type of data for the assessmentThe choice of the data in EN 15978 will depend on several aspects, including the stage of the building project, and the intended use or scope. According to EN 15978 the data (either the bill of quantities, a building description of components, or the LCA data) may be given in different types: aggregated, specific, generic or average. They describe different levels of specificity concerning the description of the building components as well as the representativeness of the LCA data.
Guidance
The description of the quantities of the building products may vary significantly in terms of precision between the early design of a building project and the very late stages the project.Practitioners should always ensure that the building description is consistent between the various documents used, as the documents are all not produced at the same, time and building projects change over time. For example, it is essential to check whether the energy consumption results are based on assumptions regarding the mass of the building products, rather than the quantity take-off available in separate documentation.Generally, in early design, the level of description is low, as the design team does not know yet exactly what the specific description of the elements will be. For instance, the reinforced concrete in early design stages is described mainly in ml or m3, with a ratio for the reinforcing steel included in the concrete.However, during the detailed design, the level of description of the building elements is increased. At this stage, the building-related data may be more precise for some building elements (e.g. for the façades), whereas for others (e.g. the floor coverings), it may be only roughly taken into account until the actual building occupants are found.Common units that can be found in the building’s project documentation are: ml, m2, m3, unit etc. The practitioner should be aware of the potential differences in terms of the functional or declared units of LCA data available in LCA software for buildings and some of the units of the building-related-data (the quantity take-off). Wherever possible, the practitioner should use the most appropriate LCA data that correctly match the building-related data for the corresponding stage of the project.

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