Now, let’s move on to the Space‐by‐Space Method (our alternative to the Building Area Method).
===========================================================
In this method, our lighting watts allowance for the building is the sum of the calculated allowance for each space.
===========================================================
For each space, we look up the allowance for that space type and multiply it by the LPD we will see in the example table on the next page.
===========================================================
Please note we are allowed to trade off watts between spaces; if I don’t use all the watts I’m allowed in the high bay manufacturing area, I can use those watts somewhere else such as in the offices.
51
Here we see a small part of the space‐by‐space table.
======================================================================
As an example, if our building had a private office that measured 10’ by 14’, we would then be allowed 154 watts for that office (10 x 14 x 1.1). We then add up the individual allowances for each space to arrive at our total interior lighting power allowance for the building … well, almost.
52
Here we see that the allowance for sales area has a footnote.
This footnote states “Where lighting equipment is specified to be installed to highlight specific merchandise in addition to lighting equipment specified for general lighting and is switched or dimmed on circuits different from the circuits for general lighting, the smaller of the actual wattage of the lighting equipment installed specifically for merchandise, or additional lighting power as determined shall be added to the interior lighting power determined in accordance with this line item.” This gives us additional lighting power allowance in retail spaces with which to highlight product as long as this additional lighting is on separate circuit from the general lighting.
53
The product areas over which the calculation may be made have been divided up into 4 different types and the allowance is based on what kind of product is displayed in each area. To accommodate smaller spaces, the project gets a one time base allowance of 500 watts besides the calculated allowances.
54
Here we see what kinds of products determine the different sales area types.
=============================================================
It should be noted that the authority having jurisdiction can approve the ‘move’ of product to a higher retail area type when provided with documentation showing that it is justified based on requirements for visual inspection, contrast or other critical display issues.
55
Let’s take our earlier retail example. If 40000 sq.ft of the space is dedication to furniture sales (which is type 3) then we get 500 + 1.4 times 40,000 for a total of 56,500 watts available to us to provide accent display lighting on the furniture as long as that lighting is circuited separate from the general lighting. This additional allowance is ‘use‐it‐or‐lose‐it’. If we only use 40,000 watts to provide our product accent lighting, we do NOT get to use the remaining 16,500 watts anywhere else.
56