Wat 01 Water consumption
(all buildings)
| Number of credits available | Minimum standards |
|---|---|
| 5 | Yes |
Aim
To reduce the consumption of potable water for sanitary use in new buildings from all sources through the use of water efficient components and water recycling systems.
Assessment criteria
The following is required to demonstrate compliance:
Up to five credits
| 1 | An assessment of the efficiency of the building's domestic water-consuming components is undertaken using the BREEAM Wat 01 calculator. |
| 2 | The water consumption (L/person/day) for the assessed building is compared against a baseline performance and BREEAM credits awarded based upon Table 40. |
| 3 | The efficiency of the following 'domestic-scale' water-consuming components must be included in the assessment (where specified): |
| 3.a | WCs |
| 3.b | Urinals |
| 3.c | Taps (wash hand basins and where specified kitchen taps and waste disposal unit) |
| 3.d | Showers |
| 3.e | Baths |
| 3.f | Dishwashers (domestic and commercial-sized) |
| 3.g | Washing machines (domestic and commercial or industrial sized). |
The BREEAM Wat 01 calculator defines the building types and activity areas for which the above components must be assessed.
| 4 | Where a greywater or rainwater system is specified, its yield (L/person/day) is used to offset non-potable water demand from components that would otherwise be supplied using potable water. |
| 5 | Any greywater systems must be specified and installed in compliance with the national best practice standard. |
Checklists and tables
Table 40: BREEAM credits available for percentage improvement over baseline building water consumption
| No. of BREEAM credits | Percentage improvement | ||
|---|---|---|---|
| Precipitation zone 1 | Precipitation zone 2 | Precipitation zone 3 | |
| 1 | 12.5% | 12.5% | 12.5% |
| 2 | 25% | 25% | 25% |
| 3 | 40% | 35% | 35% |
| 4 | 50% | 45% | 40% |
| 5 | 55% | 55% | 50% |
| Exemplary | 65% | 65% | 60% |
Please refer to compliance note CN3.1 and Figure 5 for information on BREEAM precipitation zone classifications. Also, please note that for some building types an alternative approach to compliance must be used to award credits (for further information please refer to Methodology and the BREEAM Wat 01 calculator).
Compliance notes
| Ref |
Terms |
Description |
|---|---|---|
|
Shell and core (non-residential and residential institutions only) |
||
|
CN1 |
Applicable assessment criteria |
All criteria Shell only: This issue is not applicable. Shell and core: This issue is applicable subject to CN1.1 Refer to Appendix D – Shell and core project assessments for a more detailed description of the shell and core assessment options. |
| Shell and core assessments |
Shell and core Compliance for this issue must be assessed on the basis of all water-consuming components and greywater or rainwater systems specified and installed by the developer. Components or systems listed in the criteria and sited within tenant areas that are not being specified by the developer, but will be specified by the tenant do not need to be assessed for a shell and core project. |
|
|
Residential - Partially fitted and fully fitted |
||
|
CN2 |
Applicable assessment criteria - Single and multiple dwellings |
Partially fitted: All criteria relevant to the building type and function apply subject to CN2.1. Fully fitted: All criteria relevant to the building type and function apply.Refer to Appendix E – Applicability of BREEAM New Construction to single and multiple dwellings, partially and fully fitted for a more detailed description of residential assessment options. |
| Water efficiency and partially fitted dwellings |
Compliance for this issue must be assessed on the basis of all water-consuming components and greywater or rainwater systems specified and installed by the developer. Components or systems listed in the criteria that are not being specified and installed by the developer, but will be specified by the new homeowner, do not need to be assessed. The minimum standard is still applicable. Where the homeowner will be responsible for installing all of their own water fittings and components, no credits can be awarded, and the minimum standard is not applicable. |
|
| General | ||
|
CN3 |
No fittings present |
Where a project under assessment contains none of the specified components, the performance specification for components provided in facilities in an adjacent and accessible building must be used in the calculation, i.e. those facilities most likely to be used by the occupants and visitors of the assessed building. This rule also applies where a project under assessment consists solely of an extension to an existing building, i.e. where the extended building contains no new sanitary facilities because there are facilities present within the existing building. |
| Precipitation Zones (by Köppen) |
Please refer to Figure 5 for information on the BREEAM precipitation zone classification.
For more information and guidance on the Köppen climate classification refer to Scope of BREEAM International New Construction. |
|
| Country specific | ||
| National best practice standard for specifying and installing greywater and rainwater systems |
Please refer to the country reference sheet to locate the appropriate national best practice standards in the country of assessment. Alternatively, please demonstrate applicability as follows:
OR
|
|
| Building specific | ||
|
CN5 |
Hotel type | Please use 'Other buildings type calculator' tab within the Wat 01 calculator tool. The alternative Wat 01 method (see Methodology) should be used for the assessment of a hotel. |
Methodology
A building's water efficient performance is determined using the BREEAM Wat 01 calculator in one of two ways, using either the standard approach (common building types) or alternative (other building type) approach. Each approach is summarised below.
Standard Wat 01 method
The standard BREEAM method determines water efficiency (measured in L/person/day and m³/person/yr) for a building based on the building's actual component specification and default usage patterns for the building type and its activity areas. This modelled output is compared with the same output for a baseline component specification and the percentage improvement used to determine the number of BREEAM credits achieved.
The baseline component specification is equivalent to the water efficiency of industry standard components (see Table 41), steered by the minimum levels required by the Water Supply (Water Fittings) Regulations. The BREEAM percentage improvement benchmarks have then been determined based on progressively more efficient standards for water-consuming components and, for the higher levels of performance, the specification of greywater and rainwater systems.
The standard approach is the default method for calculating water efficiency of a BREEAM-assessed building and is that used for most of the common building types, where usage data are available. For buildings types where usage data are not available, and therefore the standard approach for determining performance cannot be used, an alternative approach to compliance must be used (described below). Refer to the BREEAM Wat 01 calculator for the current list of building types which can be assessed using the standard approach.
Alternative Wat 01 method
Where it is not possible to use the standard approach to determine the building's water consumption total (L/person/day) the assessment can be completed on an elemental basis, as follows.
- Using the list of applicable domestic-scale water-consuming components (see criterion 3), determine those that are specified or present in the assessed building.
- Compare the actual specification for each component type with the table of water efficient consumption levels by component type (Table 41) to determine the level of performance for each type. Note that the volumes quoted are maximums for that level and the % WC or urinal flushing demand is a minimum for that level.
- Define each component's level of performance in the 'Other building type calculator' worksheet of the BREEAM Wat 01 calculator.
- For the alternative approach, the calculator applies a building type specific weighting to each component level to reflect its 'in-use' consumption relative to the other components present. A component with high 'in-use' water consumption therefore has a larger weighting than one with lower 'in-use' consumption and contributes relatively more to the building's overall level of performance under this BREEAM issue.
- The weightings are derived from data on actual water consumption per day from non-domestic buildings, sourced from BNWAT221. They can be found in the BREEAM Wat 01 calculator.
- Based upon the performance categorisation of each component type and the component weighting, the calculator will determine an overall level of performance and award the relevant number of BREEAM credits as follows:
| Greywater or rainwater level achieved | ||||
|---|---|---|---|---|
| Precipitation zones 1 and 2 | Precipitation zone 3 | |||
| Overall component level | _ | 4 | 5 | 5 |
| Baseline | 0 credits | 1 credit | 2 credits | 1 credit |
| Level 1 | 1 credit | 2 credits | 3 credits | 2 credits |
| Level 2 | 2 credits | 3 credits | 4 credits | 3 credits |
| Level 3 or 4 | 3 credits | 4 credits | 5 credits | 4 credits |
| Level 5 | 4 credits | 5 credits | 5 credits | 5 credits |
Note:
- An innovation credit for exemplary level performance can be awarded where the component specification achieves level 5 and > 95% of WC or urinal flushing demand is met using recycled non-potable water.
- Due to the use of the weightings, the overall component level achieved will not necessarily be a whole number, e.g. component level 4. Where this is the case the methodology will always round down to the nearest component level and therefore BREEAM credits level, e.g. if the component specification achieved is 3.6 credits, the actual number of credits awarded is 3 credits (the methodology will not round up to 4 credits because the performance specification for 4 credits has not been achieved).
- Where the assessed building development has multiple specifications for the same water-consuming component type, the number of fittings and component level achieved for each specification can be entered in the 'Other building type calculator'. Using this information, the calculator will determine the building's aggregated performance level for that component type.
Please note: while attempts have been made to align the benchmarking of both methodologies described above, they determine performance in different ways. The number of BREEAM credits awarded by each method could therefore differ for the same water component specification. This could lead to variation in the credits achieved when applying BREEAM New Construction to a number of different building types that form a part of the same overall development.
Component type
Table 41 outlines the standards, by component type, used to define the performance levels set in BREEAM. These defined levels of efficiency have been steered by a range of published sources of information (see references2) and therefore reflect robust levels of typical, good, best and exemplary practice.
Table 41: Water efficient consumption levels by component type
| Component | Performance levels (quoted numbers are minimum performance required to achieve the level) | |||||||
|---|---|---|---|---|---|---|---|---|
| Base | 1 | 2 | 3 | 4 | 5 | Unit | ||
| WC | 6 | 5 | 4.5 | 4 | 3.75 | 3 | Effective flush volume (litres) | |
| Wash hand basin taps | 12 | 9 | 7.50 | 4.50 | 3.75 | 3 | litres/min | |
| Showers | 14 | 10 | 8 | 6 | 4 | 3.50 | litres/min | |
| Baths | 200 | 180 | 160 | 140 | 120 | 100 | litres | |
| Urinal (2 or more urinals) | 7.50 | 6 | 3 | 1.50 | 0.75 | 0 | litres/bowl/hour | |
| Urinal (1 urinal only) | 10 | 8 | 4 | 2 | 1 | 0 | litres/bowl/hour | |
| Greywater or rainwater system |
Precipitation zone 1 |
0% | 0% | 0% | 25% | 50% | 75% | % of WC or urinal flushing demand met using recycled non-potable water |
|
Precipitation zone 2 |
0% | 0% | 0% | 0% | 25% | 50% | ||
|
Precipitation zone 3 |
0% | 0% | 0% | 0% | 0% | 15% | ||
| Kitchen tap: kitchenette | 12 | 10 | 7.50 | 5 | 5 | 5 | litres/min | |
| Kitchen taps: restaurant (pre-rinse nozzles only) | 10.30 | 9 | 8.30 | 7.30 | 6.30 | 6 | litres/min | |
| Domestic sized dishwashers | 17 | 13 | 13 | 12 | 11 | 10 | litres/cycle | |
| Domestic sized washing machines | 90 | 60 | 50 | 40 | 35 | 30 | litres/use | |
| Waste disposal unit | 17 | 17 | 0 | 0 | 0 | 0 | litres/min | |
| Commercial-sized dishwashers | 8 | 7 | 6 | 5 | 4 | 3 | litres/rack | |
| Commercial or industrial sized washing machines | 14 | 12 | 10 | 7.50 | 5 | 4.50 | litres/kg | |
Please note that specifying components for a building in accordance with the above levels will result, in most cases, in the corresponding number of BREEAM credits being achieved. However, please bear in mind that the component specifications above are akin to thresholds between each level. Therefore caution should be exercised when defining a component specification for a BREEAM-assessed building using exactly the same levels as the threshold levels. It is recommended that, where Wat 01 BREEAM credits are being targeted, the performance of a particular building's component specification is verified using the BREEAM Wat 01 calculator before committing to a particular specification and ordering or installing components. This will provide greater assurance that the component specification achieves the targeted number of BREEAM credits.
Water-consuming components - data requirements
Table 42: This table defines for each component type the appropriate data that will need to be collected from manufacturers' product information to complete the assessment
| Domestic component | Data requirements |
|---|---|
|
WCs |
Actual maximum or, where dual flush, effective flush volume in litres/use. |
| Urinals | Flush volume in litres/use for single use flush urinals. For cistern fed systems, the flushing frequency/hour and cistern capacity in litres. |
| Taps |
Flow rate of each tap, at full flow rate in litres per minute measured at a dynamic pressure: For high pressure (Type 1) taps: 3 - 0.2 bar (0.3 - 0.02 MPa) OR For low pressure (Type 2) taps: 0.1 - 0.02 bar (0.01 - 0.002 MPa). (EN 200:2008, Sanitary tapware, single taps and combination taps for supply systems of type 1 and 2. General technical specifications). This includes any reductions achieved with flow restrictions. |
| Showers |
Flow rate of each shower at the outlet using cold water (T 30oC), in litres per minute measured at a dynamic pressure: For high pressure (Type 1) supply systems: 3 - 0.2 bar (0.3- 0.02 MPa) OR For low pressure (Type 2) supply systems: 0.1 - 0.05 bar (0.01 - 0.005 MPa) (EN 1112:2008, Sanitary tapware. Shower outlets for sanitary tapware for water supply systems type 1 and 2. General technical specifications). |
| Kitchen taps | Maximum flow rate litres/minute. |
| Baths |
Capacity to overflow in litres. Taps on baths should not be included in the calculation, as the water consumption from bath taps is taken account of in the use factor for baths. The calculation of water consumption for baths will assume 40% of the capacity to the overflow. This is to reflect that:
|
| Dishwasher | Litres/cycle for domestic applications or appliances or litres/rack for commercial applications or appliances. |
| Washing machine | Litres/use for domestic applications (for a typical wash cycle) or appliances, or litres/kg for commercial applications or appliances, e.g. in hotels. |
| Waste disposal unit | Flow rate in litres/minute. |
Unspecified water-consuming components
As the methodology and BREEAM credits for water efficiency compare the building's modelled water consumption performance against the performance of a baseline specification for the same component types, where a component type is not specified it is not accounted for in the methodology, i.e. the component is excluded from both the proposed and baseline building. Therefore no benefit is gained in terms of BREEAM performance, by deciding not to specify a particular component. However, the methodology will reflect the reduction in overall water consumption (litres/person/day) for the building, as a result of not specifying a particular component.
Buildings with greywater and rainwater systems
The following information is required where a greywater or rainwater system is specified:
Rainwater:
- Collection area (m²).
- Yield coefficient (a coefficient (%) to recognise that some rainwater is lost due to splashing, evaporation, leakage and overflow etc. This coefficient will vary depending on the surface from which the rainwater is collected).
- Hydraulic filter efficiency (a coefficient (%) to recognise the efficiency of the hydraulic filter).
- Rainfall (average mm/year).
OR
- Daily rainfall collection (litres) calculated in accordance with credible and verifiable national or local data, e.g. a regional, national or international meteorological organisation, data source or equivalent.
Greywater:
- Manufacturer or system designer details.
- The percentage volume of waste water collected (and reused) from the following (where relevant); wash hand basins, showers, kitchen basins, dishwashers, baths, washing machines and sources of waste water from non-domestic components.
Where greywater or rainwater systems are specified, a minimum level of component efficiency must be achieved to award 4 or 5 BREEAM credits and the exemplary level credit. This is to avoid awarding a higher number of BREEAM credits where performance from less efficient fittings is offset by the specification of a greywater or rainwater collection system.
The intention behind this is to ensure demand reduction is prioritised before offsetting consumption. Where a greywater or rainwater system is specified or installed, the component specification must achieve a percentage reduction in water consumption (over the baseline specification) equivalent to that required for 2 credits, i.e. a 25% improvement. Where this level is achieved, all of the total water demand met by greywater or rainwater sources can contribute to the overall percentage improvement required to achieve BREEAM credits. If it is not achieved, the percentage of greywater or rainwater allowable will be equivalent to the percentage improvement in water consumption achieved for the component specification, i.e. percentage improvement on baseline performance.
For example, if a 20% improvement only is achieved, and therefore the building is not meeting the 25% requirement, only 20% of the water demand met via greywater or rainwater sources can be used to offset water consumption from the micro components. This minimum requirement does not apply where only 1, 2 or 3 credits are sought or where no greywater or rainwater system is specified, i.e. percentage improvement is based solely on the water efficiency of the micro-component specification.
BRE Global may allow some exemptions to this rule in instances where a particular fitting type requires a high flow rate due to specialised end user requirements, and its specification prevents compliance with 25% improvement.
Buildings with a mixture of different functional areas
For the majority of buildings using the standard Wat 01 method, the BREEAM Wat 01 calculator defines the building type and range of different water-consuming activity areas within that building; for example, a retail development with sales area and goods storage or an office that includes a canteen and gym. However, where carrying out a single assessment of a building or development which consists of a diverse mix of activity areas or building types, all of which can be assessed separately within the calculator, the following applies:
Determine the building's total water consumption performance by carrying out separate assessments for each relevant activity area or building type. On completion of each assessment, the assessor will need to determine the percentage improvement as follows:
Where:
I = Overall improvement (%)Tn Act = the modelled net water consumption (L/person/day) for each building type Tn Base = the modelled baseline water consumption for the corresponding building type Tn Occ = the total default occupancy rate for the corresponding building type.
Where greywater or rainwater systems are specified, the assessor should take care to avoid unintended double counting of the yield from such systems and using it to offset demand for each activity area or building type.
Fixed water use
The BREEAM water efficiency calculation includes an allowance for fixed water use. This includes water consumption for vessel filling (for building users' drinking water), cleaning in kitchens and food preparation in buildings with a catering facility. Fixed uses are included to provide greater accuracy in the reporting of the building's overall estimated water consumption. As these uses are fixed for both actual and baseline building models, their totals do not influence the achievement of BREEAM credits.
Other permissible component demand for non-potable water
The focus of this BREEAM issue is the performance of the building's permanent domestic-scale water-consuming components. Where a greywater or rainwater system is specified, the yield from the system should be prioritised for such uses, i.e. WC or urinal flushing. However, where the building demonstrates that it has other consistent (i.e. daily) and equivalent levels of non-potable water demand, and such demands are intrinsic to the building's operation, then it is permissible for the demand from these non-domestic uses to be counted, i.e. the demand for rainwater or greywater yield from such systems or components can be used as well as, or instead of, non-potable water demand from the building's WC or urinal components. Examples of consistent and intrinsic demands could include laundry use in hotels or residential institutions, or horticultural uses in garden centres, botanical gardens and golf courses. Demand for general landscaping and ornamental planting irrigation are not considered as equivalent or intrinsic by BREEAM.
Other permissible sources of non-potable water
The methodology allows for the collection and recycling of non-potable water from the relevant components listed in the criteria, i.e. taps, showers, baths and dishwashers or washing machines. In addition, where non-potable water is collected from a non-domestic component or source that is intrinsic to the building, then the amount collected can be accounted for in the methodology. This could include, for example, wastewater from active hygiene flushing, i.e. a regular hygiene flushing programme to minimise poor water quality in a potable cold or hot water system. In order for the method to account for this total, the design team will need to confirm to the assessor the yield from the component or system (in litres) and the frequency of that yield (in days), i.e. if once a week, the frequency would be seven days.
Evidence
| Criteria | Interim design stage | Final post-construction stage |
|---|---|---|
| All |
A completed copy of the BREEAM Wat 01 calculator. The relevant sections or clauses of the building specification or design drawings confirming technical details of:
OR Where detailed documentary evidence is not available at this stage; A letter of instruction to a contractor or supplier or a formal letter from the developer giving a specific undertaking, providing sufficient information to allow the water calculations to be completed. |
As design stage for post-construction information OR Written confirmation from the developer that the appliances or fittings have been installed as specified for the Design Stage OR An assessor site inspection report and photographic evidence confirming installation of components in accordance with a compliant specification. |
Additional information
Relevant definitions
- BREEAM Wat 01 calculator
- The BREEAM Wat 01 calculator is a method for the assessment of water efficiency in most common types of new buildings. The calculator assesses the contribution that each internal domestic-scale water-consuming component (as listed in the criteria) has on whole building water consumption. The calculator and accompanying guidance on its application is available separately from this Scheme Document. Please note, the calculator is a compliance tool and not a design tool for water demand and drainage systems. The tool uses default usage and occupancy rates to provide a benchmark of the typical consumption given the specified fittings (in L/person/day and m³/person/year) and their impact on the building's overall water efficiency. Due to the impacts and differences of actual user behaviour and occupancy rates, the results of the method will not reflect directly the actual water use during building operation. The results from the methodology should, therefore, not be used for the purpose of comparison with, or prediction of, actual water consumption from a non-domestic building.
- Domestic-scale components
- Domestic-scale components include water consumed (potable and non-potable) by internal building components including kitchen taps, wash hand basin taps, baths, showers and dishwashers, WCs, urinals, washing machines and waste disposal units.
- Effective flush volume
- The effective flush volume of a single flush WC is the volume of water used for one flush. The effective flush volume of a dual flush WC is the ratio of full flush to reduced flush. This is taken to be one full flush for every three reduced flushes for non-domestic buildings and one full flush for every two reduced flushes in domestic (residential) buildings or areas. The effective flush volume can therefore be calculated as follows, using a 6/4 litre dual flush volume WC as an example:
- Non-domestic: {(6 litre x 1) + (4 litre x 3)}/4 = 4.5 litre effective flushing volume (for a 6/4 dual flush WC)
- Domestic: {(6 litre x 1) + (4 litre x 2)}/3 = 4.67 litre effective flushing volume (for a 6/4 dual flush WC).
- Greywater recycling
- The appropriate collection, treatment and storage of domestic wastewater (which is defined as that discharged from kitchens, baths or showers, laundry rooms and similar) to meet a non-potable water demand in the building, e.g. WC flushing, or other permissible non-potable use on the site of the assessed building.
- Potable water
- Drinking quality water that is taken from a connection to the main water supply to the building, which may be from the public water supply or from a private supply such as from groundwater via a borehole.
- Non-potable water
- Any water other than potable water, also referred to as unwholesome water.
- Rainwater recycling
- The appropriate collection and storage of rainwater run-off from hard outdoor surfaces to meet a non-potable water demand in the building, e.g. WC flushing, or other permissible non-potable use on the site of the assessed building.
Other information
