[Bldg-rate] LEED+90.1 Process/Plug Loads Conundrum

Nick Caton ncaton at smithboucher.com
Fri Apr 30 10:54:39 PDT 2010

Something new occurred to me this week and I'd love to hear others'


LEED prescribes baseline/proposed energy models to follow ASHRAE 90.1
with a caveat:  the "process energy costs" must total 25% of the
baseline energy costs.  By extension, 90.1 requires the same
loads/schedules be applied to the proposed model as they have to match.
As an aside, the LEED EAc1 templates appear to calculate/check this
using process energy consumption (not cost), but that's not what I'm
getting at...


I just had a typical case where I had to inflate the baseline internal
miscellaneous equipment loads to get to 25%.  These additional loads
were substantial enough that when applied to the proposed model/design,
I ran into many unmet cooling hours for the equipment capacities


Then I realized:  We can define additional equipment electricity loads
but simultaneously apply a multiplier (in eQuest anyway - I expect this
is feasible other programs also) to reduce/negate the corresponding heat
load contributions.  This results in the energy consumption/costs
showing up correctly in the final results/reports, but does not
artificially inflate the internal loads that the baseline/proposed
systems must handle.


Would this practice (which incidentally can be a time saver) of
accounting for extra process/miscellaneous loads without extra thermal
contributions be in line with the intent of ASHRAE/USGBC?  It would
still normalize the otherwise unstandardized process consumption/costs
of the baseline/proposed models between different building types...


On the other hand, if it really is the intent of USGBC to add arbitrary
additional internal heat loads to our models that our actual designs
were not designed and sized for, does it follow that we should allow the
proposed models to autosize cooling equipment/fan capacities and not
specify them (this would seem incongruous with 90.1 to me)?









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