[Bldg-rate] Bldg-rate Digest, Vol 18, Issue 3
Christina A. Snyder
CASnyder at ic.org
Tue May 4 00:26:24 PDT 2010
Wow, Nick, you're ahead of me on this one.
I didn't know that the multiplier on the lighting loads added to the
power density without adding to the heat loads. Not sure how that is
possible, except that one can opt to make a theoretical model not follow
the laws of physics if one wants to. I've used that multiplier as a way
to try to make the energy model we do as a part of a commercial energy
rating match the reality of the energy bills of the existing building.
My experience has been that Equest is consistantly way overestimating
the power consumption of a building (nearly a factor of 2 on the last
building I did), so I have to use that multiplier to try to rein it in,
and I wish there were multipliers on all the other electric input
fields, not just lighting.
I'm about to go tomorrow to my 1st Equest training (in Milwaukee) - I'm
jumping right in at the intermediate level of training after going about
as far as I can w/ beating my head against the brick wall of trying to
work with this energy DESIGN software to model existing buildings I have
to rate. I find the help files /documentation to be pathetic - tends to
tell me no more than I can read off the screens of the wizards. I'm
looking for info as to what Equest is assuming when you give it the
various inputs and why, as well as better descriptors of what the inputs
on the drop-down menus in the wizards are. This info you gave me on the
magical properties of the multiplier to vary power density without
varying internal heat gains is a good example of the kind of info I need
about Equest, and I'm going to check it out at the training. I may not
get many good answers though, as the trainers state that they are
focused on the use of the software for design, and that they aren't
going to get into HVAC equipment much - basically all of my problems are
areas they are planning to dodge.
Since you posted to the Bldg-rate list, I'm curious to know if you (and
others on this list) are also predominately doing simulations of
existing buildings, and if so, what your evaluation of the available
energy modeling software is for this purpose. I can see why one would
want to overestimate consumption in DESIGN software - then your
customers think you are wonderful when the buildings actually use less
energy then predicted. But its not very helpful when using the software
to RATE existing buildings - I have to struggle to tweak the model to
even come close to approximating the reality of the energy bills, else
the Energy Efficiency Measures I plan to recommend look laughable. I'd
love to find some easily used affordable energy modeling software that
actually does a good job of simulating existing buildings.
I can't answer as to the intent of USGBC or ASHRAE as to requirements
for LEED. It wouldn't surprise me if they were choosing to ad arbitrary
loads to buildings that would result in oversized equipment - that's the
old-school engineering mindset that is getting in our way now as we want
to move towards ultra-efficient building. I've also been trained by the
Passivhaus Institute to model with their PHPP software, and you can't
get to the Passivhaus Standard with oversized equipment. Sometimes it
seems change is glacially slow, but at least LEED is moving in the right
direction now with their latest release.
Thanks for a thought provoking query,
architect, Certified Passive House Consultant, and commercial energy
Clean Energy Coalition
On Fri, 30 Apr 2010 12:01:00 -0700,
bldg-rate-request at lists.onebuilding.org said:
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> Today's Topics:
> 1. LEED+90.1 Process/Plug Loads Conundrum (Nick Caton)
> Message: 1
> Date: Fri, 30 Apr 2010 12:54:39 -0500
> From: "Nick Caton" <ncaton at smithboucher.com>
> To: <bldg-rate at lists.onebuilding.org>
> Subject: [Bldg-rate] LEED+90.1 Process/Plug Loads Conundrum
> <FCEBC0C28321F7479789B25A13030F6901208708 at sandbinc2.sbi.smithboucher.com>
> Content-Type: text/plain; charset="us-ascii"
> 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)?
> NICK CATON, E.I.T.
> PROJECT ENGINEER
> 25501 west valley parkway
> olathe ks 66061
> direct 913 344.0036
> fax 913 345.0617
> Check out our new web-site @ www.smithboucher.com
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> End of Bldg-rate Digest, Vol 18, Issue 3
Christina A. Snyder
casnyder at ic.org
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