[Equest-users] building shade effect (UNCLASSIFIED)

[Joe Huang]

Bobby, others,

I beg to differ, but I find it hard to believe that a louver system with the density  
shown on your picture on a building with a WWR of 60 will have only a 1% impact on the 
building energy use.
What is the percent impact on the cooling energy use?  In an office building in a tropical 
climate, as implied in your post,  solar heat gain through windows can easily make up 
30-50% of the building's cooling load, so if the solar is reduced by 30-50% due to 
louvers, I would expect a cooling load reduction around 10-20%,  and maybe total building 
energy around 5-10%.

When you interpret the results from eQUEST, remember that the program doesn't model at all 
the UV or long-wave interactions, etc., that you've mentioned to explain why the savings are
so low.  If you are modeling the louvers as a BUILDING-SHADE, make sure that the shade is 
positioned correctly in front of the glazing, that the TRANSMITTANCE and SHADE-SCHEDULE are
appropriately defined, and that you also adjust the SKY-FORM-FACTOR and GND-FORM-FACTOR 
for the glazing, since the BUILDING-SHADE affects only the direct solar radiation and not 
the diffuse solar radiation. This is particularly important in a tropical location where 
there is a lot of diffuse radiation.  The form factors are meant to be the amount (solid 
angle) of sky or ground
that the glazing "sees".  The defaults are 0.50 and 0.50, i.e., half sky and half 
ground.   If you input only the SFF, DOE-2 would assume 1-SFF as the GFF.  I've had 
trouble with that recently,
so it's better to also input GFF at 0.50, or a little higher if you think there's 
reradiation due to the louvers.

Joe

Joe Huang
White Box Technologies, Inc.
346 Rheem Blvd., Suite 108D
Moraga CA 94556
yjhuang at whiteboxtechnologies.com
www.whiteboxtechnologies.com
(o) (925)388-0265
(c) (510)928-2683
"building energy simulations at your fingertips"


On 5/31/2012 11:53 AM, Eurek, John S NWO wrote:
> Classification: UNCLASSIFIED
> Caveats: NONE
>
> It is all up to interpretation.  The key to interpreting the information is to first know what you want the information to say, then find the data to back it up.
>
> If you want to sell the solar shades, focus on the reduction of solar radiation. (Truth: A small part of the whole)
> If you want to talk the architect out of it, highlight that it only saves 1%. (Truth: Energy savings comes from having many small energy savings methods working together.)
>
> 1 important question - How much does the architect like the solar shade?
>
> If the solar shades are just an option, the next step is to do a life cycle cost analysis.  You already have the energy model which is the hardest part.  If you can find the cost of the solar shades and energy costs you could do it in 20 minutes or less.
>
> If the solar shades are his pet, it won't be too hard to find numbers telling him how wonderful they are.
>
> *his/hers
> -----Original Message-----
> From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of R B
> Sent: Thursday, May 31, 2012 1:26 PM
> To: eQUEST Users List
> Subject: Re: [Equest-users] building shade effect
>
> Have not followed the thread in detail - but here are some things I have found about windows - first off not a whole lot of saving at the yearly-building level. If you look at the peak breakdown for a window - the U-value related conductance is 2/3rds vs the solar radiation (1/3rd) - atleast for the one model that I was looking at. As others have noted, almost 40-50% of the energy consumption is from lights/plug loads.
>
> You might want to look at just the perimeter zones and see what happens to the energy consumption reduction in just those zones?
>
> You can also look at just the LS-D reports to see what the % savings are. Sometimes it helps in saying that reductions are x% of the cooling load (without considering the HVAC inefficiencies) - which will be a higher number.
>
>
>
>
> On Thu, May 31, 2012 at 9:16 AM, Nick Caton<ncaton at smithboucher.com>  wrote:
>
>
> 	Feeling confident in your modeling approach is very much important, but before running deep into alternate methods, I would seek perspective on what % improvement is even feasible.  Perhaps a 1% net improvement is quite impressive, all things considered?  Considering static shades can be simultaneously helpful and harmful thermally over a year, a few iterations exploring different transmittance values may be enlightening.
>
> 	
>
> 	Doing so, you might be able to establish a ceiling for maximum possible improvement with such shades, and suggest a more optimized exoskeleton spacing or similar.
>
> 	
>
> 	There may also be a lesson in here about how to present results in a fashion that both informs and appeases the design team.  Perhaps the shades may not have an impressive net annual baseline % improvement, but significant thermal comfort and glare issues are averted, and cooling plant capacities can be lowered by slicing the summertime solar loads.... I would also caution to check the solar loads are indeed cutting down as anticipated if you aren't sure of your approach.
>
> 	
>
> 	Best of luck!
>
> 	
>
> 	~Nick
>
> 	
>
> 	cid:489575314 at 22072009-0ABB
>
> 	
>
> 	NICK CATON, P.E.
>
> 	SENIOR ENGINEER
>
> 	
>
> 	Smith&  Boucher Engineers
>
> 	25501 west valley parkway, suite 200
>
> 	olathe, ks 66061
>
> 	direct 913.344.0036
>
> 	fax 913.345.0617
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> 	www.smithboucher.com<http://www.smithboucher.com>
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> 	
>
> 	From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Umesh Atre
> 	Sent: Thursday, May 31, 2012 8:30 AM
> 	To: Bobby Sy; equest-users at lists.onebuilding.org
> 	Subject: Re: [Equest-users] building shade effect
>
> 	
>
> 	
>
> 	Bob,
>
> 	What is the project location and how is the building oriented? Do these louvers run across the entire height of the building?
>
> 	If you have a heavily internal load dominated (office) building, the building skin effect might be minimal, but then again the shading design
>
> 	you have in this project looks pretty dense and assuming you have a need for cooling, my gut feeling is that 1% is on the lower side.
>
> 	
>
> 	
>
> 	
>
> ________________________________
>
> 	From: equest-users-bounces at lists.onebuilding.org [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of Bobby Sy
> 	Sent: Wednesday, May 30, 2012 10:19 PM
> 	To: equest-users at lists.onebuilding.org
> 	Subject: [Equest-users] building shade effect
>
> 	Hello everyone!
>
> 	
>
> 	I am working on a project, a high rise office building. The architect added louvers as part of the design which I admire for sophistication. Attached is a picture that shows the louvers outside for shading. But, when I did the initial run, the effect of the louvers is only around 1% energy improvement from the baseline.
>
> 	
>
> 	Please let me know if there is a better way to do it in eQuest. What I did was to measure the louver thickness and proportioned it to the glass area that it covers. I put the fraction as "Transmittance:" in Building and Fixed Shades properties. Doe 2 help says:
>
>
> 	TRANSMITTANCE
>
>
> 	Fraction of incident solar radiation that is transmitted by the shading surface. The default value is 0.0, which means the surface is opaque. A value greater than 0.0 represents a device that passes some solar radiation, such as a tree, lattice, or fabric. Using SHADE-SCHEDULE allows seasonal variation in transmittance. Daylighting calculation assumes TRANSMITTANCE = 0.
>
> 	
>
> 	The design team quite find it hard to believe that the louvers have very minimal effect. I told them to consider the window to wall ratio (almost 60%) and that fact that they will be using a clear glass, even with these louvers partial UV rays still pass through the gaps that spreads allover the glass surface that adds to the heat load for air conditioning. Ive noticed to some of my other projects in tropical countries, building shades don't have much effect to energy efficiency. Did anyone encounter the same result with building shades?
>
> 	
>
> 	
>
> 	Thanks,
>
> 	
>
> 	Bob
>
>
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> Classification: UNCLASSIFIED
> Caveats: NONE
>
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