[Bldg-sim] Window Film and Building heating

Duggin, Cory Cory.Duggin at tlc-eng.com
Tue Nov 4 09:02:20 PST 2014


I agree with Bill.  It sounds like you are losing the passive reheat of the solar gain when you decrease the shading coefficient.  We see this a lot in hospitals.

Cory Duggin, EI, LEED AP BD+C
Associate/Energy Engineer
TLC Engineering for Architecture
direct:

615-346-1939



From: Bldg-sim [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of Bishop, Bill
Sent: Tuesday, November 04, 2014 10:40 AM
To: John Aulbach; bldg-sim at onebuilding.org
Subject: Re: [Bldg-sim] Window Film and Building heating

John,
One idea is to check the timing of your heating savings. Maybe you are saving reheat energy?
~Bill

William Bishop, PE, BEMP, BEAP, CEM, LEED AP | Pathfinder Engineers & Architects LLP
Senior Energy Engineer

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From: Bldg-sim [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of John Aulbach
Sent: Tuesday, November 04, 2014 11:33 AM
To: bldg-sim at onebuilding.org<mailto:bldg-sim at onebuilding.org>
Subject: [Bldg-sim] Window Film and Building heating

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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