B-27 Assessment of operational water use in complete LCA

Aspect B-27 Assessment of operational water use in complete LCA
Description
The operational water use assessment includes water used during the operation of the building, together with the associated environmental impacts and aspects, including the production of drinking water and wastewater treatment. A link between domestic hot water and energy use should also be considered.

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 Operational water use should be assessed using a bottom-up approach (see guidance). The upstream and downstream processes linked to the operational water use should be modeled using specific LCA data (e.g. EPD based on industry), or else may be modeled with generic LCA data (e.g. if no specific data are available, or if the impact categories do not match the goal and scope of the study). Assessment of the water consumption during the use phase should be included in the LCA studies in order to be consistent within the overall assessment methodology (the use of a ‘net fresh water’ indicator for the various life cycle phases). Water consumption during the use phase is usually the most important, compared with the other phases of the life cycle.
Rules from:

EN 15978

7.4.4.8 Boundary of the operational water use (Module B7)EN 15978 states that the boundary of operational water use should include water used during the normal operation of the building together with the associated environmental impacts due to its treatment (before and after use). This includes drinking water, water for sanitation, domestic hot water, irrigation, water for heating, cooling, ventilation and humidification, and other specific water uses (e.g. fountains, swimming pools and saunas). Water consumption of non-building-related equipment (e.g. dishwashers, washing machines) could be included within the assessment. This issue should be reported separately.

EN 15804

7.3.3.3 B6, use of energy and B7, use of water
Guidance
In order to calculate the water consumption for complete LCA, a methodology based on a bottom-up approach should be used. It consists in estimating the total consumption by taking into account the characteristics of each water consumption device (e.g. 6 L flushing system), the use factor (use frequency) and all the other influencing parameters (e.g. dwelling surfaces, external use, etc.). The bottom-up approach is the most suitable, since it allows a finer sensibility analysis, and hence more efficient performance improvements/optimization.In addition to the volume of water consumed, the environmental impacts linked to the production, respectively wastewater treatment should also be considered.For a complete LCA, all types of water used to produce domestic water (whether for drinking or not) should be considered, i.e. public grid water (drinking water), rainwater, underground water, surface water and greywater. The particular national regulations on the use of different types of water should be specified (i.e. rainwater or greywater). For example, in France rainwater use was regulated in 2008.The French regulation allows the use of rainwater for only two uses indoors (WCs and floor washing), and experimentally for washing machines.For each type of technology, specific LCA data (e.g. EPD on waste water treatment provided by the industry) may be used in a complete LCA. If the practitioner intends to assess impact categories outside the scope of a PCR (e.g. EN 15804), the corresponding EPD on waste water treatment may not be suitable. In this special case only, generic LCA data may be used (assuming that the full inventory is available, and makes it possible to calculate the various impact categories available, e.g. in the ILCD Handbook).

Any comparative assertion should be supported by a sensitivity analysis of the various parameters and hypotheses considered during the assessment, especially regarding user behaviour. The baseline scenario should be developed by using default values for all the parameters, defined according to statistics on the most common current values. Regular updating is therefore necessary (as the various equipment characteristics evolve relatively quickly).


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