[Bldg-sim] Window Film Product Claims

Nick Caton ncaton at smithboucher.com
Tue Jan 15 13:15:39 PST 2013


Hi John,

As I understand the topic (at a baser level than others on these lists), R-values / U-values are a kind of flawed metric in and of themselves when discussing window films.  Films can perform magical feats when it comes to cutting solar loads (perhaps turning your building into a 2-way mirror in the process), but quantifying that result into a U-value is a loopy path at best, as no thin/transparent coating prevents heat transfer by conduction in the same sense typical insulation does.

Regardless of manufacturer claims, I would be averse to modeling the effects of such films as a "u-factor factor" if charged with determining ROI.  Also keep in mind solar loads aren't always a bad thing if we're talking annual energy bills.

See also:

The_limitations_of_R-values_in_evaluating_radiant_barriers<http://en.wikipedia.org/wiki/R-value_(insulation)#The_limitations_of_R-values_in_evaluating_radiant_barriers>

Here's a (for cost?) paper that appears to be evaluating this exact sort of issue utilizing eQuest/WINDOW.  Abstract/highlights there are intriguing.  Possibly includes procedure you could draw from?  I recognize Rongxin from the mailing lists here - perhaps he could fill you in further?

http://www.sciencedirect.com/science/article/pii/S0378778811005251

Regards,

~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
www.smithboucher.com

From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of John Aulbach
Sent: Tuesday, January 15, 2013 2:10 PM
To: bldg-sim at lists.onebuilding.org
Subject: [Bldg-sim] Window Film Product Claims


Hi Folks:

This has to do with modeling in general.

I have a Window Film manufacturer with a product called Enerlogic VEP35 window film. It is apparently applied to the inside of a window.

The manufacturer claims that this product lowers the U-Value of single pane glass (1/4" or 6 mm) from 1.109 to 0.6. And with no air space between the film and the glass. "Revolutionary new technology"

Has anyone ever run into this product before? Why does this claim sound "too good to be true" ??

Thanks.

John Aulbach
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