B-19 Operational energy demand for new buildings – Boundaries and scenarios for complete LCA

Aspect B-19 Operational energy demand for new buildings – Boundaries and scenarios for complete LCA
Several parameters can influence the results of the operational energy demand for the use stage of buildings, such as the selection of uses (i.e. building-related or non-building-related uses). European standards (EN 15804/EN 15978) recommend taking account of priority building-related uses such as heating and cooling. However, non-building-related appliances can significantly influence the energy needs of building-related uses (e.g. the thermal gain of appliances decrease the level of heating demand). How can this aspect can be addressed for in complete LCA of new buildings?

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 construction products screening LCA simplified LCA complete LCA
Provisions For complete LCA of a new building, every building-integrated system should be accounted for (including building-related uses considered in the EPBD and other building-integrated systems). Non-building-related systems may be also accounted for. For complete LCA of new buildings, every energy use occurring in the building may be included.  Scenarios and data for calculation of the energy demand for each energy use should be specific to the object of the study.
Rules from:
EN 15978: Boundaries for operational energy use
8.6.5 Scenarios for operational energy use – Module B6
For complete LCA, building-related uses considered by the Energy Performance of Buildings Directive (2002/91/EC) should be accounted for. Building-related uses (heating, cooling and air conditioning, ventilation, heating for provision of domestic hot water, lightning) should be calculated either according to national calculation methodology or with the help of thermal dynamic simulation.When thermal dynamic simulation is used, hourly consumption data are required to provide precise information on the energy demand, and to enable the calculation of exported energy in the case of on-site production (see aspect ‘Operational energy calculation – Allocation of on-site energy production’, Module 6)Scenarios for calculation of the energy consumption of building-integrated systems and non-building-related uses may reflect statistical or conventional user behaviour. For example, the type and number of appliances and the frequency of use should be calculated according to statistical data if no accurate data are available. The expected performances of user appliances may be taken into account within the calculation if available (e.g. the consumption of a refrigerator may be estimated according to its certified efficiency). For electricity uses the quantification of impacts should take seasonal and daily variation of the electrical mix into account. When available, hourly data should be used first. If they are not available, monthly average data should be used, or annual average data as a last resort.Link between energy consumption values and environmental impacts

Once the energy consumption values have been calculated, they need to be associated with a specific LCA data, e.g. based on industry data if available; otherwise choose generic data of the corresponding process. For example, the number of kWh of electricity in a French building project should be associated with the generic LCA data representing the average mix for the French context.

Other energy sources such as fuel, natural gas, wood and district heating also need a generic LCA data describing only the combustion. To this purpose, the infrastructure (e.g. the boilers) should be accounted for as technical equipment. This equipment contributes to the embodied impacts of a building along with the building products.

Depending on the goal definition of the study (cf. aspect ‘Classifying the decision context between situation A from B from C’), it is possible to choose, e.g. for the electricity consumption, an average mix or a marginal mix. The marginal effects are usually modelled using consequential modelling (situation B according to the ILCD Handbook). A final option is to choose hourly LCA data, particularly in the case where the thermal simulation results are provided on an hourly basis. This remark is part of the EeBGuide aspect ‘Dynamic LCA data for assessing the impact of electricity consumption’).

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