[Bldg-sim] Fwd: Re: RE: Voodoo Engineering

Fri May 21 08:22:53 PDT 2010

Chris,

You make a good point, and it also can apply to centrifugal chillers,
which are sometimes most efficient at 60-80% loaded.  But you still have
to remember that the client has to pay for the larger equipment, which
costs more, plus larger system components (which cost more) and more
space (which costs more).

You also maake a good point about the system loads 90% of the time,
which raises an interesting question regarding sizing for optimum
operating efficiency.  What if we sized certain types of equipment to
meet the most predominant loads within their most efficient capacity
ranges?  That is not difficult when using hourly simulation software.
Of course, you have to keep an eye on peak loads and capacities.  I
haven't thought this through yet, but I'll bet someone else has.

Thanks,
Glenn

-----Original Message-----
From: "Chris" [mailto:chris at zed-uk.com] 
Sent: Thursday, May 20, 2010 7:13 PM
To: Haynes, Glenn; backer at uidaho.edu; paul at zed-uk.com; thomasv at iit.edu
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Fwd: Re: RE: Voodoo Engineering

Glenn,

Oversize isn't always bad! A condensing boiler is generally at its most
efficient at < 20% of its capacity.

All the same, the mid-season is largely ignored when it comes to sizing.
Ridiculous really, when you think this is where the plant will be 90% of
the time.

Perhaps this is more of an issue when you are shifting large amounts of
chilled water to various pieces of zone equipment but has anybody
considered Valve Authority? Unfortunately my experience is limited when
it comes to the nitty gritty of piping networks. But, I do know one
thing: valve response is not linear, especially if there is a
substantial head in the system. My hunch is mid season control could get
really messed up if plant has spare capacity but designers haven't been
quite as generous with pipe sizes.

Such questions should be in the domain of simulation in the next few
years.

Chris

on 20/5/10 8:15 PM, "Haynes, Glenn" <Glenn.Haynes at kema.com> wrote:

> Brad,
>
> I did HVAC design consulting for 14 years, and I used to oversize 
> systems just like everyone else.  Now I am an energy conservation 
> programs evaluator, and have discovered the extent and negative 
> impacts of over sizing.  Not speaking for all designers who oversize, 
> I did it mainly out of willful ignorance.  It was easier for me to 
> loosely calculate the peak loads and then beef those estimates up 
> enough to safely cover and mistakes or false assumptions than it was 
> to calculate the loads with enough confidence to properly size the 
> systems.  I believed in the old adage that too much is just right from

> my perspective, because it minimized risk.
>
> But now I have to measure the effects of excessive over sizing and see

> the results, some of which are poor humidity control, short cycling, 
> reduced system operating efficiency and higher first cost to the
owner.
> My DOE2 models usually indicate peak (I mean absolute hourly peak 
> loads) at about 20% less than Manual J loads, on average, for 
> residential applications.  But even Manual J allows up to 20% above 
> their calculated loads, which have already been calculated using 
> conservative estimates for most inputs that are not explicitly 
> defined.  The observed
> (measured) field results have proven the average residential AC system

> to be about 70% to 75% oversized, with some as high as 200% (that's 3 
> times the peak load).  20% to 25% over ASHRAE's 2.5% design standard 
> is acceptable to me now, but anything above 25% without some 
> overriding owner requirement (plans to add on to the current building,

> etc.) begins to waste the owner's resources (from first cost to energy

> and maintenance costs) and reduce the lifetime of the equipment while 
> at the same time decreasing his overall level of comfort through 
> limited latent performance.
>
> There!  You obviously rubbed a sore spot in my emotional make-up, but 
> I appreciate the opportunity to make a point.  And the point is this: 
> no matter how good your modeling software is, the outcome is still in 
> the hands of the user.
>
> Glenn
>
> -----Original Message-----
> From: bldg-sim-bounces at lists.onebuilding.org
> [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Acker, 
> Brad
> Sent: Thursday, May 20, 2010 1:45 PM
> To: Paul Carey; Chris Yates; Varkie C Thomas
> Cc: bldg-sim at lists.onebuilding.org
> Subject: Re: [Bldg-sim] Fwd: Re: RE: Voodoo Engineering
>
> I do not do modeling on a daily basis so I'm not as experience as many

> other here. I do agree modeling just for LEED is silly. I have seen 
> modeling inform designs, reduce loads, and SIZE SYSTEMS. This last 
> part is what most bugs me. Why do people put so much effort into 
> models and then not use them to size the systems? Preventing over 
> sizing is a great benefit of modeling. What is your experience with 
> using models to size systems? Why do engineers fall back on the vendor

> based programs and 9 out of 10 times end up over sizing systems?
>
> Brad Acker, P.E.
>
> -----Original Message-----
> From: bldg-sim-bounces at lists.onebuilding.org
> [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Paul 
> Carey
> Sent: Thursday, May 20, 2010 3:42 AM
> To: 'Chris Yates'; 'Varkie C Thomas'
> Cc: bldg-sim at lists.onebuilding.org
> Subject: Re: [Bldg-sim] Fwd: Re: RE: Voodoo Engineering
>
> Just to add a couple of points to this interesting debate.
>
> I see the problem being that, as we increasingly set more defined 
> limits regarding energy modelling and its role in building regulation,

> we are seeing buildings that are being built and designed to purely 
> meet compliance.  This is in some part is useful as it brings all 
> buildings up to a minimum standard, the flip side of that problem is 
> that it also means, that to many developers this means there is no 
> incentive to strive for alternatives or innovative solutions.  It can 
> also allow therefore lead to the use of simpler tools that meet those 
> prescribed limits, but really don't push the boundaries of engineering

> design enhancement of buildings.
>
> The correct implementation and use of energy modelling need not be a 
> hindrance to projects nor be seen as a necessary "extra" or evil if 
> you consider the design process as a whole.  If you use the tools at 
> the concept or schematic design phases, this can quantitatively 
> confirm an engineer's instinct or gained experience in way that will 
> enable them to show compliance later on. It will then allow the team 
> to come to a decision on the most energy efficient but also compliant 
> route of design earlier on in the design stage and should stop the 
> repeat iteration of designs as the building design progresses and 
> therefore reduce design costs and with luck increase productivity and
profit accordingly.
> Fanciful dream perhaps, but it does work.
>
> I visited an architect a while back and he said to me "Why do I need 
> to do modelling, I know the principles of good low energy design, I 
> can read books
> and learn more if I need to".   To which I replied, "Well every time
you
> send me a job to check for building regulation compliance 3 weeks 
> before it goes before a planning team, I normally have to tell you 
> what you need to do in terms of meeting compliance as your buildings 
> are consistently failing and you then have to rush to make those 
> changes.  I am effectively designing your buildings for you, so if you

> want to continue without using energy modelling then please carry on, 
> and I'll continue to design your buildings."
> As you can imagine this was one of those Eureka moments for this 
> Architect, as I waved my red rag in front of his face.
>
> My tuppence worth.
>
> Paul
>
> -----Original Message-----
> From: bldg-sim-bounces at lists.onebuilding.org
> [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Chris 
> Yates
> Sent: 20 May 2010 07:55
> To: Varkie C Thomas
> Cc: bldg-sim at lists.onebuilding.org
> Subject: Re: [Bldg-sim] Fwd: Re: RE: Voodoo Engineering
>
> Varkie
>
> Vast subject. Kudos for condensing it whilst conveying all the 
> necessary meaning.
>
> We are now at a point where Energy Modellers are at the very least 
> specialist engineers. In fact, you could say the best are indeed 
> "wizards"!
>
> Chris
>
> Sent from my iPhone
>
> On 19 May 2010, at 21:35, Varkie C Thomas <thomasv at iit.edu> wrote:
>
>> Since my response has ended up on Bldg-Sim, I might as well include 
>> the attachment with the response which gave my views 
>> <Building-Energy-Programs-VCT.doc>
>> I am including the attachment that I included with my earlier 
>> response
>
>> to John Eurek. Using energy programs is like voodoo engineering if 
>> you
>
>> don't understand its engineering basis.  It analyzes the various 
>> options quantitatively.  It cannot be used as a magic black box.
>> Experience and judgement have to applied to the results.
>>
>> ----- Original Message -----
>> From: Eric O'Neill <elo at MichaelsEngineering.com>
>> Date: Wednesday, May 19, 2010 12:03 pm
>> Subject: RE: Voodoo Engineering
>>
>>> John,
>>>
>>> The purpose of energy modeling is to identify differences between 
>>> two
>
>>> energy related setups. The idea is to tell you how much you could 
>>> conceivably save by switching from one design to another. This is 
>>> usefulfor a payback analysis or life cycle cost analysis.
>>>
>>> Hope this helps, (I'm really not trying to be inflammatory :) )
>>>
>>> Eric
>>>
>>> -----Original Message-----
>>> From: Eurek, John S NWO [mailto:John.S.Eurek at usace.army.mil]
>>> Sent: Wednesday, May 19, 2010 11:19 AM
>>> To: Varkie C Thomas
>>> Cc: Eric O'Neill; cmg750 at gmail.com
>>> Subject: RE: Voodoo Engineering
>>>
>>> Varkie, I read your attached paper.
>>>
>>> "Energy programs are external to the design process. The results are

>>> not used to generate construction drawings."  This may be my #1 beef

>>> with energymodeling.  What is the purpose?
>>>
>>> If you say, to save energy...  It does not.
>>>
>>>
>>> John Eurek
>>> LEEP AP
>>>
>>>
>>> -----Original Message-----
>>> From: Varkie C Thomas [mailto:thomasv at iit.edu]
>>> Sent: Wednesday, May 19, 2010 10:08 AM
>>> To: Eurek, John S NWO
>>> Subject: Voodoo Engineering
>>>
>>> Academia institutions and research centers tend to attach 
>>> disproportionate amount of importance to energy modeling.  Most them

>>> have not dealt withreal buildings.  Attached are my views on energy 
>>> modeling.
>>>
>>> ----- Original Message -----
>>> From: "Eurek, John S NWO" <John.S.Eurek at usace.army.mil>
>>> Date: Wednesday, May 19, 2010 8:14 am
>>> Subject: Re: [Equest-users] Compliance rule set for Oregon
>>>
>>>>
>>>> I would prefer Lynn work to ban/destroy/do-away-with energy
>>> modeling.>
>>>> Any chance this voo-doo engineering will go away any time soon?
>>>> It is only
>>>> statistical analysis with no meaningful/useful results for anyone.
>>>>
>>>> As a community I think we are going in the wrong direction for
>>> the
>>>> rightgoals.
>>>>
>>>> -----Original Message-----
>>>> From: equest-users-bounces at lists.onebuilding.org
>>>> [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of
>>> Carol
>>>> Gardner
>>>> Sent: Wednesday, May 19, 2010 12:30 AM
>>>> To: Scott Criswell
>>>> Cc: equest-users at lists.onebuilding.org; curt.strobehn at eesinet.com
>>>> Subject: Re: [Equest-users] Compliance rule set for Oregon
>>>>
>>>> All,
>>>>
>>>> Lynn Bellenger will soon be the first female president of ASHRAE..
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