[BLDG-SIM] eQuest Dbl Skin Sim

[Callan, David]

There are no commercially available energy simulation tools, I am aware of,
that will simulate the complexity of a double skin façade.  The performance
of these systems varies dramatically with the type of façade and its
interaction with the building's HVAC system.  At best, I would suggest you
dig into the research and publications to determine what kind of system you
wish to model, then begin to develop a set of assumptions you can use in the
analysis. When modeling an advanced façade, one should go back to first
principles.  Best of luck!


David P. Callan, MS, PE, CEM
Senior Associate
LEEDTM Accredited Professional
Syska Hennessy Group, Inc.
Email:dcallan at syska.com 
http://www.syska.com 


-----Original Message-----
From: stvgates at pacbell.net [mailto:stvgates at pacbell.net] 
Sent: Tuesday, January 27, 2004 8:36 PM
To: BLDG-SIM at GARD.COM
Subject: [BLDG-SIM] eQuest Dbl Skin Sim

See comments imbedded below ........

----- Original Message ----- 
From: "Kevin Krudwig" <kdk_71 at yahoo.com>
To: <BLDG-SIM at GARD.COM>
Sent: Saturday, January 24, 2004 8:26 PM
Subject: [BLDG-SIM] eQuest Dbl Skin Sim


> Hello,
> Can anyone tell me:
>
> Is it possible to simulate a double skin façade with
> eQuest?
> If so, how to?

I am not aware of an accurate way to simulate a double skin facade in
eQUEST, but a quick back-of-the-envelope analysis may suffice to draw
conclusions about this concept:

1.  Assume your building costs $150/sq.ft. to build, and that the
double-skin is 10% of that cost, or $15.
2.  Assume that energy for the building costs $1.25/sq.ft./year, and that
the double-skin saves 25% of the total energy budget, or $0.31/sq.ft./year.
(In many buildings, lights and plug loads comprise about half the energy
cost, and this analysis assumes the double-skin has no impact on either.  So
this guestimate is based on the double skin saving 50% of the HVAC costs,
which seems quite optimistic.)
3.  The simple payback is then $15/$0.31 = 48 years.  This assumes an
opportunity cost of 0%, and no additional operating and/or maintenance
costs. If the actual interest rate is 5%,
the annual interest cost is $15*0.05 = $0.75/year; or more than twice the
energy savings.  Given the interest cost, the double-skin would have to
eliminate ALL of the HVAC energy, and a portion of the lighting as well.

So, is a double-skin facade worthwhile?  Unless the assumed cost of the
double skin is high by a factor of at least 3, this concept does not appear
worth considering.

Does anyone have any better information on construction costs and energy
savings of an actual building using a double-skin facade?  To me, this
concept is so far out in left field that I don't understand why there is so
much interest in it.

>
> Is it possible to simulate a dynamic façade with
> eQuest?

I'm not sure what you mean by a dynamic facade.  In regards to dynamic
shading in eQUEST, you can define a schedule that modifies the transmittance
of a building shade.

> One that incorporates Photovoltaics?

Yes, eQUEST simulates photovoltaics.  The PV modules can be mounted
stand-alone, or incorporated as part of a building shade.  Be sure to use a
recent version, as the photovoltaic algorithms were upgraded last fall.
Study the PV-MODULE and ELEC-GENERATOR sections in the DOE-2.2 Dictionary.
>
> Thanks
> Kevin K.
>
>
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