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

Thu May 20 12:57:32 PDT 2010

That is a good point. It is almost impossible to not oversize the HVAC system from the prospective of designing heating and cooling equiplment.  No one can really know what will really happen after the building is built.  Actual use in buildings are alwasy different from the design intent as there are big uncertainties for real buildings. Of course it is very important to try to get accurate information during the design phase. But we may more focus on three things,
1: Continue to monior the actual building energy use and equipment efficiency in buildings.  These measurements should be very helpful to find some ways to save energy for the newly finished buildings.  
2: Improving part load performance in HVAC equipment may be more important than not oversizing HVAC equipment.  It seems there is no way to design the very appropriate systems to suit the actual use in buildings.  For example, the building loads may be changed a lot from year to year, day to day, hour to hour.  
3: For HVAC designer,  maybe it is necessary to understand which factors are key variables to size the HVAC system. Maybe for some buildings, the weather conditions (99% or 99.5%) will make big differences in sizing HVAC equipment. But for other buildings, the building use, like internal heat gains, is more important. This can help us which factors we should focus on. 

Terry

________________________________
From: "Haynes, Glenn" <Glenn.Haynes at kema.com>
To: "Acker, Brad" <backer at uidaho.edu>; Paul Carey <paul at zed-uk.com>; Chris Yates <chris at zed-uk.com>; Varkie C Thomas <thomasv at iit.edu>
Cc: bldg-sim at lists.onebuilding.org
Sent: Thu, 20 May, 2010 20:12:09
Subject: Re: [Bldg-sim] Fwd: Re: RE: Voodoo Engineering

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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