Part G - Water Supply
Since the introduction of SAP 2009, Part G water efficiency calculations are now required for all_new dwellings under the new Part L1a 2010. It has not yet been determined who is responsible for these calculations, but it is epect that energy assessors will be able to complete the calculations under a competant persons scheme.
The calculation has been devised to limit water consumption in new dwellings by setting an upper usage limit in litres per person per day. The calculation method is straightforword and takes into account the flow rates of each water consuming/providing part of a dwelling. A standard usage time has also been set for each peice of equipment and so a total usage in litres can be determined. Sould the calculated target be above that specified in Part G for each code* level, the building will fail a SAP assessment. Aerating taps, showers and water efficient w/c's will be essential.
* The code for sustainable homes
Information required for Part G calculations
Manufacturer information of the flow rate of tap, shower, bath, toilet, washing machine and dishwasher is required for all Part G water efficiency calculations.
The limits of the calculated consumption are,
| Performance Target* | Maximum consumption of potable water (litres/person/day |
| Compliance level | 125 |
| Code for sustainable homes 1 and 2 | 120 |
| Code for sustainable homes 3 and 4 | 105 |
| Code for sustainable homes 5 and 6 | 80 |