EXPRESS FILMS EXPERT QUIZ #1 - OCTOBER 2011

[EWF]

Does the NFRC ignore the 1200-2500nm range?

Definitely not. They have to be measuring ALL of the energy that comes within the entire range.

But I am sure they are aware how much it tapers off once you get north of 1100-1200 as well as the big gaps where it drops to zero on the way up to 2500.

-Howard

[EWF]

ATTN anyone reading this thread.

There may be more to be learned here about this subject than perhaps anywhere on the internet. You certainly will not read information like this on a manufacturer's website. Mr. Vq is tremendously knowledgeable and has expanded my understanding of this subject.

Thank you Vq.

-Howard

[vquestfilms.com]

ATTN anyone reading this thread.

There may be more to be learned here than perhaps anywhere on the internet. You certainly will not read information like this on a manufacturer's website. Mr. Vq is tremendously knowledgeable and had expanded my understanding of this subject.

Thank you Vq.

-Howard

Howard,

My name is "Rob" and I do look forward to meeting you in person. I'm not trying to win a discussion here, I'm just going through my process of reasoning to get down to the facts. I truly enjoy discussing with one's like yourself the technical side of our industry. Thank you for your comments.

We can all work to elevate the window film industry by unifying our message and processes so that they agree with other professional industries such as ASHRAE, and the glazing industry. We have at our fingertips one of the best products next to lighting that can increase building efficiency and return on investment. Solar cannot touch our return, wind cannot touch it either, and we are far cheaper and environmentally friendly than glass replacement... we have a good thing here, let's not squander it by arguing.

[EWF]

I'm not trying to win a discussion here.

Well Rob - you have won me over. I can't not say that I have interacted with anyone that knows this subject better than you obviously do.

I probably have more questions now than we began, but I understand it better than before. Thank you.

I wish you a safe journey to SEMA. I am headed there tomorrow.

-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!

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

I didn't miss anything. There is a wealth of knowledge in the thread but I didn't see a grand slam as you did.

[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

I didn't miss anything. There is a wealth of knowledge in the thread but I didn't see a grand slam as you did.

Yeah but you are top notch in my book and been around alot longer, you probably knew most of this. For those of us that didnt its great reading. Have a safe trip to SEMA

[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!

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

I didn't miss anything. There is a wealth of knowledge in the thread but I didn't see a grand slam as you did.

Yeah but you are top notch in my book and been around alot longer, you probably knew most of this. For those of us that didnt its great reading. Have a safe trip to SEMA

Just a misunderstanding Tinthoss. Dang English language has still got me guessing! I wish I knew half of what Howard or Rob knows on the subject!! I think the discussion would be better in the general forum. Howard started this thread in his own section as a quiz with prizes I look forward to seeing them both at SEMA...................... THoss you have a safe one, I have to finish getting ready for the show so I can watch the game tonight. You da mang!

[Guest Pacific Islander]

WOW!

One of the very best threads I've read to date in tintdude. At times, I couldn't tell the difference between Howard or Rob. Guys...please don't take that as any type of insult.

I've learned a lot from this post. I don't think any other rep. from any other company can "hang" besides company engineers and scientists. If you two were ever to start a company together, OUCH...factories all over the world would have a problem.

With all that you both have gone back and forth on...I have a question for both of you;

If it were ONE "formula", "measurement" or whatever you want to call it, what would you use? Please...just name one. IR?, TSER?, SHGC?, SC?, etc...?

Cheers to both of you!

Pacific Islander

[Tinitman]

SHGC

Interesting read and I agree with most said.

[EWF]

For those who have been monitoring this thread, it's about to get turned on it's head as some new very interesting information has just come to light (pun intended).

A great deal of focus has been concentrated on the fact that the EDTM BTU meters top out at 1,100nm. While this is absolutely true, as it turns out - it does not matter.

Here is the reason why as well as a few examples to help us understand it:

Although glass does transmit IR, it only does so within the lower end of the NIR spectrum. We can see a practical example of this by using a TV remote control thru a glass cabinet door. The remote emits a red light within the range of 800-900nm and the TV will respond to the commands.

But when you start get above this range, the glass itself attenuates the wavelengths. Here are three practical examples of how we can demonstrate this in everyday life. I am going to use examples in 3 different spectral ranges above 800-900.

Example #1.

Many of us are familiar with Inrfa-Red motion sensors, which are attached to alarm systems. Imagine such a sensor inside a building and just two feet from a window (for example). A person on the inside standing 25 feet (or more) from the sensor can and will trip it. But a person walking outside the building and just 2 feet from the sensor will not. The glass will completely attenuate those wavelengths.

Now stand on the outside and aim a powerful IR bulb at the sensor and move it around as much as you wish. Or you can even place your entire body up against the glass. Although you are just 2 feet away, you can't trip that sensor from the outside. Although your body and the bulb is emitting IR, the example illustrates the ability of glass to attenuate IR energy.

Example #2.

Many of us are also familiar with InfraRed night vision goggles. For this example let's imagine that you are in your home at night looking out a 3 cars in your driveway. Two of the three cars have been sitting there for days and one was just parked there a minute ago. The engine block of the car which was just driven is close to 195F and emitting a very large amount of IR. The other two are cold. You step outside momentarily and observe the 3 cars with your night vision IR equipment. The car with the hot engine is clearly and easily visible since it is emitting a lot of heat energy. Now go inside your home and repeat the same procedure thru the glass. The night vision goggles no longer reveal which car has the hot engine. The glass is attenuating all of the energy at those wavelengths.

Example #3.

This example moves higher up the spectrum (1550-1650)nm and deals with fiber optic cables, which are actually bundled strands of thousands of hair thin hollow glass tubes which carry light. Typically, 1550-1650nm wavelengths are used in the communication industry. Each of those individual glass strands carries the pulsating beams.

Obviously, it is critical that each strand be able to transmit the energy without interfering with the thousands of other adjacent strands, which are bundled together in the same fiber optic cable. If the 1550-1650 wavelength energy were able to jump outside of each glass strand, the cable would be nothing more than a giant short circuit. But it is not. It works perfectly well because the energy is enclosed within a glass strand that does not transmit the energy to an adjacent strand.

Fiber optic cables work because light at that wavelength is not transmitted thru the glass walls which make up each strand in the cable.

Getting back to the EDTM BTU Meter:

Because the glass itself will attenuate the wavelengths once you get above 900-1,000nm and the meter goes all the way up to 1,100, it is therefore measuring the energy that counts. Above 1,100nm, glass attenuation becomes the controlling factor.

Now you know why window film manufacturers quote IR data generally in the 1,000-1,075nm range. Once you get above that, the glass itself attenuates the wavelength. Any performance they quote above that range is attributable to the glass, not the window film.

More on using the meters: A full-scale analysis vs. taking a reading in the field:

Rob is correct in his statements that a full-scale energy analysis and audit is superior to a hand-held meter to demonstrate how a window film installation will impact a building. But such an analysis takes into account a multitude of factors, only one of which is the window film.

The question then becomes, if all other factors are equal, how do we know which of several films we are considering is best suited for our objective? Can we really rely upon a BTU meter for this critical information? The answer is yes and here is why:

Rob points out that we should use energy and not temperature. He also contends that SHGC is what really counts. Rob is 100% correct on both statements.

But, although these measurements are not the same and should not be confused, they are directly related. Films with higher IR transmission (within the ranges that matter) will have a higher SHGC. Films with lower IR transmissions will have a lower SHGC.

Please see the following excerpt from EDTM's website:

The ability of a window to reject infrared energy will be directly related to a windows Solar Heat Gain Coefficient (SHGC). The lower the Infrared Transmission Value, the lower the corresponding Solar Heat Gain Coefficient. BE CAREFUL! Do not confuse Infrared Transmission with SHGC. These values are not the same. For instance, one cannot correctly state that a window that has an Infrared Transmission value of 20% will also have a SHGC value of 0.20. This is not correct. However it is safe to say that as the infrared transmission value of a window decreases, then so does the SHGC. Windows with high Infrared Transmission values will typically have high center-of-glass SHGC values as well. (This was my point and EDTM agrees.)

Hence, the simple question of which film is doing a better job can accurately be answered by the meter. Using the meter will not give you the precise SHGC value, but it will tell you which film does have a lower SHGC than another.

Conclusions:

#1 - The hand held meters top out at 1,100nm but the glass itself attenuates wavelengths above that. In this respect, they are reading the energy "that counts".

#2 - Although SHGC is what really matters and the meters do not give you SHGC, the film that does better with the meter will have a better SHGC value. The film that does worse on the meter will have a worse SHGC value. It is energy, not temperature that counts - but since they are directly related, knowing one value provides accurate and reliable information about the other.

#3 - For anyone that is skeptical or doubtful of manufacturer's performance claims (who can blame you) you can rely upon the meter to make a selection between films A & B. In the field, on the glass measurements will also take into account the "normal variances" that each manufacturer refers to in their disclaimers. The film that does better with the BTU meter, will do better in the full scale analysis (if all other factors are equal) and you were to actually do it.

Anyone who wants to improve their odds of being selected above their local competitors for a particular job should know their product inside and out, know the competitor's products equally well and use a BTU meter as part of a comprehensive sales presentation. It is providing useful and accurate information upon which you and the client can base a film-vs.-film decision.

-Howard