[Equest-users] building shade effect (UNCLASSIFIED)

Eurek, John S NWO John.S.Eurek at usace.army.mil
Thu May 31 08:16:52 PDT 2012

Classification: UNCLASSIFIED
Caveats: NONE

1% sounds about right.  

This is what we are here for!! Now you can walk back to the architect and let him understand that there louvers will look pretty, but only save 1%.  Maybe the money can be saved, or do the liberal things and just find another way to spend it.

If you can, run a quick model with 100% shading to see what a 'perfect' shading case would save.

Before you talk to the architect make sure you can explain why the louvers only save 1%.
1.  You are not receiving heat in the winter when you want it.
2.  The building energy use is mostly from computers, lights and outside air. Even with 100% shading you only save X%.
3.  The outside wall area to the volume of the building is small, so the skin load (insulation, shading) is less important. (Yes it is important but has a quicker diminishing return than a smaller building.  See elephant mouse analogy.)

Like I said, this is perfect use of energy modeling.  It will show if a 'good' idea is actually a good idea or a feel good idea.

[Now when you try to nail down every since variable and account for every hour of every day for LEED, the benefits of energy modeling get a little more sketchier.]

"Is Freedom a small price to pay to stop Global Warming?"

John Eurek

-----Original Message-----
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 9:19 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: 


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? 

Classification: UNCLASSIFIED
Caveats: NONE

More information about the Equest-users mailing list