[Bldg-sim] Update on Enerlogic VEP35 SR CDF

Graham Carter & Megan Lyall hamnmegs at ozemail.com.au
Tue Jan 22 11:40:07 PST 2013


NFRC ratings and the Window software historically use composite boundary conditions (convective and LW radiative).  I think they have them split now in the latest version of Window 6/7 though one would have to check the manuals etc.

Historically, an internal film coefficient of hi=8.3 W/m2 oK (sorry but I am Canadian, Australian) or so was assumed which when you do the back of the envelope is about half convective and half LW radiative.  So a lowE coat on the inner facing surface of a window (has to be exposed to air/gas to improve U-Value) would lower the radiative heat transfer coefficient leaving you with 4 or so for convection.  

Its the first time I have seen a lowE coating on a film that can be exposed to atmosphere.  I could be wrong but the Southwall XIR films use spectrally selective coatings or filters within the film raher than on the surface of the film.  We are used to seeing it on glass as a hard or pyrolytic coat on Pilkington k-glass - I am sitting next to a piece in our home study that definitely lowers the U-Value with no air gap … .  The truly spectrally selective coatings are soft and prone to oxidation if exposed to atmosphere thus why we see them in sealed air cavities.

So if Enerlogic have managed to coat a film that can be retrofitted onto a piece of glass then they have something.  I would be checking what warranty there is on the performance as it could be prone to oxidation or have UV stability issues (a historic problem with older generation retrofit films).

Regards,
Graham

On 16/01/2013, at 10:06 AM, John Aulbach wrote:

> 
> Update on Window Film Product:
> 
> I DID find the product listed in the NFRC Database. But, as you can see, it only lists one U-Value for each product. Not a Delta U. So I think the product is rated for Shading Coefficient and VT at that particular U-Value.
> 
> I also have an email into their Product rating director to confirm my suspicions.
> 
> Come, Watson, Come, The game is afoot..
> 
> John
> 
> 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 3:09 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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