[Equest-users] Simplified Modeling

[Nick Caton]

Hi Matt,

First a suggestion to avoid steering the discussion into confusion: when I say "zone" or "space" I'm consciously speaking in eQuest/DOE2 terms.

For each terminal unit, I most commonly define a single space whose boundaries represent the net interior area the terminal unit serves.  Each zone may represent multiple rooms.  It's conceivable for large models this approach can become cumbersome, but for clarity this is not defining a space for each room.  For any size project I would start with this typical approach and consider simplification strategies from there as necessary.

There's a natural emphasis we modelers place on accuracy, but keep in mind LEED & 90.1 recognize and permit you, the modeler, a lot of leeway to build simplification strategies of your choosing into the model.  For a large school, perhaps you can delete all but one of a block of similar classrooms and assign a multiplier to the remaining space/zone.  90.1 and the 90.1 User's Manual include further simplification guidance (as well as the mailing list archives).  All that said, bigger projects ultimately result in bigger models with lots of inputs - additional time investment is to be expected.

A lot of things might have gone wrong with your 'quick comparison...'  Hard to do more than speculate, but if you didn't carefully consider system quantities to ensure a level playing field along the way that would be a place to start.

Hope some of this helps!

~Nick
[cid:489575314 at 22072009-0ABB]

NICK CATON, P.E.
SENIOR ENGINEER

Smith & Boucher Engineers
25501 west valley parkway, suite 200
olathe, ks 66061
direct 913.344.0036
fax 913.345.0617
www.smithboucher.com

From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Matt Clough
Sent: Wednesday, May 23, 2012 4:20 PM
To: equest-users at lists.onebuilding.org
Subject: [Equest-users] Simplified Modeling

Ok equesters,

I imagine my problem has something to do with my understanding of thermal blocks, so I wanted to get some feedback from other modelers.

Currently, I'm performing a LEED analysis of a 166,000 f^2 school building.  I have created a space for every terminal box to accurately represent that system.  Unfortunately, this works out to one or two hundred spaces (I haven't actually counted) and a very large model that takes a lot of time to simulate.

Is it possible for me to create a model that represents each HVAC zone?  I have created a quick set of shells and air-side systems and a preliminary simulation reports almost double the energy usage as the detailed model.

If I represent the entire HVAC zone as one space (one eQuest zone), what is the best approach to represent the terminal units?  It seems to me that using the PIU option would be like having one vav box serving an enormous room.  While that's not the reality of the situation, is that good enough for simulation?

I suppose I will report back after I tinker with this some more.

Regards,
Matt Clough
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