[Bldg-sim] Window Film and Building heating

Joe Huang yjhuang at whiteboxtechnologies.com
Tue Nov 4 14:12:08 PST 2014


This question has been raised in the bulletin boards on several occasions, and is also 
something that I saw in a project for the Pacific Northwest about 10 years ago.

I believe the answer has to do with the HVAC sizing.  In a temperate climate, such as So 
CA, HVAC sizing is driven by the cooling load that's in turn dominated by solar gain 
through the windows.  When window film is applied, the peak cooling loads will decrease, 
resulting in smaller supply CFMs, which can also result in heating energy savings.

Joe

Joe Huang
White Box Technologies, Inc.
346 Rheem Blvd., Suite 205A
Moraga CA 94556
yjhuang at whiteboxtechnologies.com
http://weather.whiteboxtechnologies.com for simulation-ready weather data
(o) (925)388-0265
(c) (510)928-2683
"building energy simulations at your fingertips"


On 11/4/2014 8:32 AM, John Aulbach wrote:
> I have several projects coming up dealing with window film savings on large glass area 
> buildings. I need a primer to some of the results i am seeing.
>
> Logically, if you install window film on glass, you will reduce the cooling load in that 
> space, but would expect the heating load to rise. This, by the way, is in the temperate 
> So Ca climate.
>
> In BOTH cases, my improvement with window film does a killer job in reducing cooling. 
> But is also saves about 7% heating  !! I am going from a Shading Coefficient (SC) of 
> 0.75 to an SC of 0.36.
>
> Experiment. I reduced the SC to 0.01. AS boatload of cooling, but a 22% INCREASE in heating.
>
> Then I tried a SC of 0.18.  A median between the other two runs in space cooling 
> savings, but now virtually NO change in space heating.
>
> Why is there a balance point in heating? System is VAV w/RH.
>
> This BTW was double glass.
>
> I tried another building with single glass curtain wall. SC = 0.29. 3% reduction in 
> cooling.  Tried SC = 0.14. -1$ in heating. System is DDVAV.
>
> Can ANYONE enlighten me as to what is going on?
>
> John R. Aulbach, PE
>
>
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