EXPRESS FILMS EXPERT QUIZ #1 - OCTOBER 2011

[Guest VOLTRON]

I was kidding about the ice cube method being scientific, I dont think that is a true measure of testing a product because there are some many differnt factors involved. SHGC and SC are the ways to go about checking performance of films. I think there have been many discussions on how some manu's tested thier films on different parameters then most others and showed better performance. I think it is best that all manu's are playing from the same ballfield so to speak and having a uniform testing criteria. IR while doesnt show true performance and is not really a way of measureing performace will still remain in the industry and be a question that will be asked by consumers. Only thing you can do is tell them how much IR is blocked and explain to them that its only a portion of the light spectrum that causes heat and that the real ways of telling perfomance of a film is SHGC and SC.

[EWF]

I am thoroughly confused where you are going. Below is one of your first posts and you seem to be in favor of SHGC, SC, and NFRC methodology.

• I do favor NRFC published SHGC/SC over IR (as you do).
  
• I do not believe that the EDTM BTU meter is a substitute for quantitative NFRC testing
  
• I do believe that the EDTM BTU meter will provide accurate and reliable relative (Film A. vs. B) testing in the field
  
• I do believe that field testing does address the concerns of those who are skeptical of published manufacturer data
  

-Howard

[flat rock stan]

Who's on first

I don't know but I would say vquest is batting cleanup and just hit a grand slam!

[TintJunkie]

I am thoroughly confused where you are going. Below is one of your first posts and you seem to be in favor of SHGC, SC, and NFRC methodology.

• I do favor NRFC published SHGC/SC over IR (as you do).
  
• I do not believe that the EDTM BTU meter is a substitute for quantitative NFRC testing
  
• I do believe that the EDTM BTU meter will provide accurate and reliable relative (Film A. vs. B) testing in the field
  
• I do believe that field testing does address the concerns of those who are skeptical of published manufacturer data
  

-Howard

I feel there are other factors involved that the BTU meter cant offer to show which film will perform better. For instance, if one film that has a higher absorption shows to perform better than a film with a lower absorption, how can it be accurate that a BTU meter shows the higher absorbing film performs better when it will most likely radiate more heat, thus potentially be less efficient?

[EWF]

This is an excellent question. Here is the answer.

Whether you are dealing with a $199 hand-held unit or a $20k benchtop model, the meters are reading the energy that reaches the probe (or sensor). There are two sources of this energy. The first is the energy that is directly transmitted thru the glazing. The second source is the energy that is absorbed by the glazing and re-radiated toward the probe. Both will register.

The primary difference (advantage) of the more expensive units is their response range (as Vq correctly points out). Due to constraints (imposed mostly by cost) the hand held units top out at about 1,100. Hand helds that go up to 1,300 are in the works. Lab models typically go higher (up to 1,400+).

Let me try to anticipate your next question: If the hand held units top out at 1,100-1,300 and the spectrum goes all the way up to 2,500 - what good are they?

The answer can be found in the graph shown in this string. Although the spectrum does go higher, you can see that a large drop off in intensity occurs above 1100-1300. Hence, although the meter can only read roughly half the spectrum, they can detect 90% or more of the total volume. As you can see in the graph, there are sections of the spectrum where 0% of energy at that wavelength reaches the earth's surface due to water & CO2 absorption.

I had reached this conclusion before I spoke with EDTM and specifically asked if my understanding was correct. Their response was that I was correct.

Although I am a very "science and math" oriented person, I do not have a college degree in physics. I do not want to go further than this for fear of rehashing this entire dust up. Let EDTM weigh in here and hopefully explain/confirm this better than I can.

-Howard

[Guest tinthoss]

Who's on first

I don't know but I would say vquest is batting cleanup and just hit a grand slam!

You dont think vquest provide a "grand slam" of knowledge on this thread? Maybe you missed the pun but there is a wealth of learning and knowledge to be had here

[EWF]

I think Vq's knowledge is a grand slam wealth of wisdom, irrespective of all other factors.

There is a controversy over my suggested use/application of the meter. Vq and I differ over the extent to which it is providing useful, accurate and reliable information upon which a Film vs. Film decision can be made in the field. It is a spirited professional disagreement.

I will now defer to the engineering team at EDTM to weigh in. I do not make a living selling their meters. I sell window film and rely upon their equipment to make sales presentations. To the extent that I am correctly using their equipment and correctly relying upon and interpreting the results, I will accept their explanation.

-Howard

[vquestfilms.com]

Howard,

If you are going to speak for me then I am obligated to jump back in and make sure I am represented accurately.

I think Vq's knowledge is a grand slam wealth of wisdom, irrespective of all other factors.

There is a controversy over my suggested use/application of the meter. Vq and I differ over the extent to which it is providing useful, accurate and reliable information upon which a Film vs. Film decision can be made in the field. It is a spirited professional disagreement.

I will now defer to the engineering team at EDTM to weigh in. I do not make a living selling their meters. I sell window film and rely upon their equipment to make sales presentations. To the extent that I am correctly using their equipment and correctly relying upon and interpreting the results, I will accept their explanation.

-Howard

Correction...

My difference with you is regarding the most accurate and recognized methodology when it comes to analyzing a film's performance and the effect that the film's performance will have on a fenestration system and the building envelope. You have added product comparison which can already be done with either NFRC film to film comparisons or IGDB records which is the accepted method in the energy professional's community.

[vquestfilms.com]

The second source is the energy that is absorbed by the glazing and re-radiated toward the probe. Both will register.

-Howard

Not so, this re-radiated energy is a much longer wavelength >2500nm so the BTU meter equipment will not pick it up. Your non-contact thermometer will pick up temperature but as we all should know there is a massive difference between measuring temperature and energy.

Let me try to anticipate your next question: If the hand held units top out at 1,100-1,300 and the spectrum goes all the way up to 2,500 - what good are they?

The answer can be found in the graph shown in this string. Although the spectrum does go higher, you can see that a large drop off in intensity occurs above 1100-1300. Hence, although the meter can only read roughly half the spectrum, they can detect 90% or more of the total volume. As you can see in the graph, there are sections of the spectrum where 0% of energy at that wavelength reaches the earth's surface due to water & CO2 absorption.

Howard,

You cannot just ignore energy that exists in the further reaches of the solar spectrum. That would be contrary to yours and my whole belief that selective measurements are an inaccurate way to determine total performance. If it exists, then you have to account for it and there are methods that do account for the spectrum 300-2500nm. It all adds up and makes a difference.

edit spelling...

[EWF]

No, you are missing a couple of important factors.

1. You are still not measuring the entire solar spectrum up too 2500nm. By measuring 300-1100nm you are only covering about 50% no matter what the intensity is.
   
2. And of that 50% that you are measuring, the crystalline silicone cell in your meter can only measure up too about .09 W/m2/nm which leaves the rest of the energy >.09 to 1.4 W/m2/nm as unmeasurable. So you are missing a good chunk of energy in the 400-750nm range.
   

Your method is selective and limited... still not very accurate.

Hi Vq,

You opined on my method. You have every right to do so. I am not an expert on metrology. I have reached out to EDTM and am awaiting their response.

-Howard