[Bldg-sim] Energy Models for Existing Buildings

[JP Beaulieu]

Hi Jim,
Here are my thoughts on the subject. That'll help me sort things out as
well.

I don't do an audit without a full year hour by hour simulation. Why?
Because we offer E Audits as a means to optimise a client's building and to
give all the details to the client in order for him to make a good
decision. BTW, we do small and large commercial and institutionnal bldg
simulations and have been using EnergyPlus for some time now.

I must say that the solutions we are proposing call for something flexible
like EnergyPlus. I was using other softwares before but I must admit that
there where times when there was little advantage of using simulation
because we had to do the savings calculations on the side using much
guessing or assumptions. Now I can make any system I like. Using bldg
exhaust air or outdoor air or a mix of the two to feed the garage
ventilation system would be easy and take out a lot of uncertainties.
I think that other softwares are fine if you just want to compare two
systemes performances in a real life bldg in a specific climate and with
specific uses. When I think of e-sim as a set of equipement (HVAC) for a
specific bldg (walls and windows, etc.) used in a specific way by the
occupants (schedules, plug loads, etc.) I realise that there is much more
interpretation and uncertainties in the latter anyway. So why bother with
hour by hour e-sim if you are not looking at what's happening every hour.
In optimisation however, I need to look at what's happening every hour.
While most other softwares are running 8760 hours most do not give you a
good visualisation of the results on that scale (i.e. hour by hour). I want
to be able to graph a pumps runtime with a room's exess heat, concurrent
cooling and heating loads, exhaust air of one room compared to the intake
of another... This is why I use hour by hour e-sim.

You mention that you are looking for the big picture. I agree but...I tend
to be carefull at not adding (and often multiplying) uncertainties.  you
know what I'm talking about. I think I change my strategy depending on the
type of building use or construction. I won't be looking too much at the
pumps if there are only a few. I might consider more the wall construction
of an older bldg, But bottom line, why bother with a pump's specifications
if you're not even sure of its runtime. What do you think?

Also, matching the bldg's energy bills helps me to validate some schedules
and HVAC operations mainly. I don't really want to be close to the bills
each time. 30% can be acceptable if you have some explanations. I look at
the patterns of real vs simulation data : monthly energy use distribution
by source and by end use, peak power demand monthly. I would like to use
benchmarking more but I didn't find much valuable information for canadian
bldgs yet.

Anyone has good BENCHMARKING data for canada? by end use mainly.
Energy Portfolio Manager (EPM) will now collaborate with Canada gov. I hope
that is good. I used it once and had a major issue with source energy since
the bldg was 100% electric. Electricity is 90+% hydro here in Montreal.

"How carefully must the energy model match define ECMs?"
I'd say how important are the results in making the right decision? also,
what does it take to have more precise information? It's a tradeoff between
the two.
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