Page 145 - The Engineering Guide to LEED-New Construction Sustainable Construction for Engineers

LEED W ater Ef ficiency 125

The FTE is then determined using the following set of equations:
j
FTE = (worker i h)/8 h where 0 < FTE ≤ 1 (2.4.1)
j,i j,i
FTE = ∑ FTE for all employees in shift j (2.4.2)
j j,i
Then the full-time employee equivalents need to be subdivided by gender. For each
shift the numbers for male and female employees may not be equal. Let FTEM and
j
FTEF be the male full-time employee equivalent and the female full-time employee
j
equivalent for shift j, respectively. To be consistent throughout the LEED submittal, the
following equality must hold for all shifts j:
FTE = FTEM + FTEF for all shifts j (3.2.1)
j j j
In SS credit 4.2, the transient occupancies are estimated as average transient
occupancies at any one time over a shift, not as the total number of transient occupants
who may go in or out of the building during the shift. This is done to estimate the peak
number of bicycle rack spaces needed at any time. However, for WE prerequisite 1 and
credit 3, the LEED-NC 2009 Reference Guide bases transient uses on the total number of
transients, not the average over the shifts. To be consistent with this, let us define TOWM
and TOWF to be the estimated total number of male and female transients, respectively,
during a day. TOW, as previously described, would be the summation of TOWM and
TOWF.
As mentioned previously, LEED-NC 2009 recommends that the typical daily fixture
usage rates for water closets and urinals be separately analyzed for the different genders,
building usages, and occupancies. Let WCUM and WCUF be the male water closet and
i i
female water closet usage rates, respectively, for various types of buildings or
occupancies. Let UUM and UUF be the male and female urinal usage rates, respectively,
i i
for various building types and occupancies. Table 3.3.1 gives some typical default
values for these daily fixture usage rates. It is important to also analyze the building
usage on an annual basis. Let ND and ND be the number of days in a year that
FTE TOW
each type of occupancy (FTE or TOW) uses the building. Usually ND is 260 days for
FTE
office buildings and 365 days for residential or retail. For college buildings, ND may
FTE
be 260 days for staff and faculty, but ND may be much less for student occupancies.
TOW
Just as in WEc2, summing the fixture usage rates times the occupancies over the various
shifts as applicable for the entire year gives the total number of times water closets and
urinals are typically used in a year (TWCU and TUU, respectively). These were
previously given in Eqs. (3.2.2) and (3.2.3) and are reiterated here:
TWCU = ND × (∑ (FTEM × WCUM ) + ∑ (FTEF × WCUF ))
FTE j i j i
+ ND × [(TOWM × WCUM ) + (TOWF × WCUF )]
TOW i i
over all shifts j and for each type of use i (3.2.2)
TUU = ND × (∑ (FTEM × UUM ) + ∑ (FTEF × UUF ))
FTE j i j i
+ ND × [(TOWM × UUM ) + (TOWF × UUF )]
TOW i i
over all shifts j and for each type of use i (3.2.3)
Lavatory faucets, showers, prerinse spray, and kitchen sink usage rates are usually not
considered to be gender-specific. It is typically assumed that the lavatory faucet is used
for every use of a water closet and/or urinal, which combined should be the same for