[Bldg-sim] Is there a quick model for double skins facades?
Marques da Silva
fms at lnec.pt
Fri Nov 12 01:32:01 PST 2010
Hi Peter
I think you are only considering DSF gap forced ventilation (/when the
air system was switched off after occupation?/). This not an issue is
it's naturally ventilated. My opinion, and I am not a designer but I've
been monitoring a few occupied DSF façades in the warm climate of
Lisbon, is that as for any other building system it has to be properly
designed having in mind location and use. I monitored really bad façades
but also façades that behave quite well allowing the interior
temperature to remain within comfort levels during weekends when HVAC is
switched off.
I don't know ROOM but TRNSYS is a good option for modelling DSF (see the
work of Haase et al).
I agree that cold climates are preferable when considering a DSF option,
but there are other issues like, for example, tall and wind exposed
façades, specially if glazzed, where inside shading is thermally a bad
option and for outside positioning fast damage is certain. Anyway owners
may allways impose a look for their building...
>
> Nick and Vikram, double skin facades or climate walls or windows have
> been around for many years now. Vikram's question is really how do you
> produce a back of the envelope calculation to see if a double skin
> façade is a viable option. Well here goes, the basic improvement by
> using a double façade is the improvement of the U value decreasing
> energy loss. Take a look around the world and the successful
> applications of double facades is mostly in regions where heating is
> the dominant energy consumer. One of the first things were learnt more
> than 30 years ago was the U value was improved so long as air was
> ventilated through the cavity, but what happened to the U value when
> the air system was switched off after occupation? which consumed more
> energy, the energy loss of the building without the function of the
> double façade or the energy consumption of the air system to maintain
> the functionality of the double façade. Beyond the improvement of the
> U value we can then start looking at improved shading coefficients and
> surface temperature control of the inside surface of the double
> façade. For these different aspects of double façade design I believe
> the design criteria was simplified in a series of tables issued in a
> couple of ISSO publications in the 80's. These documents will get you
> rough data to be able to assess whether or not the double façade is
> feasible. As far as deluxe simulation tools probably the best is the
> ROOM program by Mike Holmes and Andrew White and then there is also
> TRNSYS.
>
> Getting back to Nick's comments, I have found over the years that the
> most comments regarding double facades come from people that have
> never designed them, here I am referring to the article and not you Nick.
>
> I first started designing double facades in the late 70's in the
> Netherlands and over the years have designed quite few and completed
> quite a few repair jobs on attempted double facades. One thing I have
> learned is that if it isn't cold then the double façade is there for
> show only!
>
>
>
> *Peter Simmonds, Ph.D. *
> *Senior Associate
> Head of the Advanced Technology Group
> **IBE Consulting Engineers*
> *14130 Riverside Drive, Suite 201*
> *Sherman Oaks, CA 91423
> p: (818) 377-8220 **x246** m: (818) 219-1284 f: (818) 377-8230
>
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> *From:* Nick Caton [mailto:ncaton at smithboucher.com]
> *Sent:* Thursday, November 11, 2010 8:11 AM
> *To:* Sami, Vikram; bldg-sim at lists.onebuilding.org
> *Subject:* Re: [Bldg-sim] Is there a quick model for double skins
> facades?
>
>
>
> Hi Vik,
>
>
>
> I hate to trample over anyone's little flower patch, but I've read
> some scathing assessments of double-facades as an energy-saving
> strategy. You might want to check this and the associated references
> out:
> http://www.buildingscience.com/documents/insights/bsi-007-prioritizing-green-it-s-the-energy-stupid.
>
>
>
>
> That said you might not be satisfied until you develop your own
> conclusions. Proponents of this approach repeatedly cite benefits of
> CFD, so to give a "fair/proper" assessment any tool you work with
> would probably need to be modeling convective airflows between floors.
>
>
>
> ~Nick
>
>
>
> cid:489575314 at 22072009-0ABB* *
>
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>
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>
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>
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>
>
> *From:* bldg-sim-bounces at lists.onebuilding.org
> [mailto:bldg-sim-bounces at lists.onebuilding.org] *On Behalf Of *Sami,
> Vikram
> *Sent:* Thursday, November 11, 2010 8:59 AM
> *To:* bldg-sim at lists.onebuilding.org
> *Subject:* [Bldg-sim] Is there a quick model for double skins facades?
>
>
>
> We are doing a project in a pretty cold climate. The project design
> has a really big glass façade facing south. One of the ideas to reduce
> conductive heat loss is to create a double skin façade on the south side.
>
>
>
> Now I realize that this is going to take a fair amount of analysis
> work to design it properly. What I was wondering is if there is a
> quick analysis tool/methodology to tell if this is even feasible to go
> into more detailed analysis.
>
>
>
> Any help would be much appreciated
>
>
>
> *Vikram Sami*, LEED AP
>
> Sustainable Design Analyst
>
> 1382 Peachtree St. NE, Atlanta, GA 30309
>
> t: 404-443-7462 f: 404.892.5823 e:
> vikram.sami at perkinswill.com www.perkinswill.com
> <http://www.perkinswill.com/>
>
> *Perkins+Will.* Ideas + buildings that honor the broader goals of
> society
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