B- 25 Assessment of operational water use in screening LCA

Aspect B- 25 Assessment of operational water use in screening LCA
The operational water use assessment includes water used during the operation of the building, together with their associated environmental impacts and aspects, including the production of drinking water and the wastewater treatments. Moreover, a link between domestic hot water and energy use should 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 The assessment of the water consumption during use phase should be included into the LCA studies in order to be consistent within the overall assessment methodology (use of a “net fresh water” indicator for different life cycle phases). Moreover, usually, the water consumption during use phase is the most important, compared to the other phases of the life cycle.It should be assessed using statistical data for screening (see guidance). The upstream and downstream processes linked to the operational water use should be modeled using generic LCA data.
Rules from:

EN 15978: Boundary of the operational water use (Module B7)

EN 15978 states that the boundary of the operational water use should include water used during the normal operation of the building together with associated environmental impacts due to its treatment (before and after use). This include drinking water, water for sanitation, domestic hot water, irrigation, water for heating, cooling, ventilation and humidification and other specific water use (e.g. fountains, swimming pools, saunas). Water consumption of not building-related equipment (e.g. dishwashers, washing machines) could be included within the assessment. This issue should be reported separately.

EN 15804: B6, use of energy and B7, use of water

In order to calculate the water consumption for screening LCA, a methodology based on the statistical data on water consumption at building scale may be used (e.g. in France the average water consumption is about 50 m3/person/year for 2.3 person/dwelling [INSEE, 2006], i.e. 115 m3/dwelling/year). To volume of consumed water, environmental impacts linked to the production/adduction, respectively wastewater treatment should be associated.For the screening or simplified LCA only the most representative technologies should be considered by using a generic LCA data available in background LCI databases (e.g. ELCD, GaBi or Ecoinvent).

Additional guidance:

Some of the labeling schemes (e.g. DGNB) also use a water indicator which is based on average water consumption of the sanitary system, rainwater and grey water use. Such an indicator may be of help to calculate operational water use for simplified LCI (module B7).

Any comparative assertion should be supported by a sensitivity analysis of different parameters and hypothesis considered during the assessment, especially on the user behaviour. The baseline scenario should be development by using default values for all the parameters. The default values should be defined based on statistics on the most common values of the moment. Therefore regular update is necessary (as the different equipments characteristics evolve relatively fast).

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