I have a facility that will be LEED NCv2009 certified and is part existing and partly new. The existing fixtures include 2 showerheads, 10 WC, 2 Urinals, 8 Lavatories, however the new addition includes 6 showers, 4 lavatories and 4 WC. In the water efficiency calculation, should I set FTE to use existing fixtures and then FTE to use new fixtures? then set visitors to use existing fixtures and then visitors to use new fixtures? or should I set the calculation to adjust the usage proportional to the ratio of existing to new fixtures.?