How can I tell if I have UV protection?

I just moved into an apartment, and I would like to know if my windows have UV protection. I have various collectibles that contain plastic (and lots of white plastic) - I want to put these items on display and do not want them to yellow. Is there some sort of way I can tell if the windows have UV protection? Or even measure the amount of UV rays getting inside? I know that you can tell by looking at the window panes & looking for a logo - however I don't believe I have the logos. (I can check when I am home next)

but in any case - How can I tell, can I measure the UV rays somehow & what sort of things can i do to add protection? Thanks!

- Chris

 

Chris,

First, I am assuming that you have dual pane windows. If you have single pane, then you have no specific UV protection from the window.

There really is no way for you to measure the amount of UV energy coming in thru your windows. But you can tell if your windows have a LowE coating, which is what you need to help block the UV energy.
When it is dark, hold a lit match or a lighter close to the glass in your window.
Look at the reflection of the flame in the window and you should see either two or three flames in the reflection.
If you see two flames in reflection, then your windows don't have a LowE coating.
If you see three flames in reflection, and the "center" flame reflection is a different color than the other two, and the center reflection does not appear to be exactly centered between the two other flames then your windows do have a LowE coating.
If you see anything other than two or three, then post a message here and tell me what you are seeing.
The LowE is what gives you the UV protection.

I am going to include a bit of a primer on UV and LowE coatings, so bear with me. Hopefully, it will answer some questions that you might have.

Basic LowE coatings do two things. First, they block infrared radiation. Infrared radiation is heat. The warmth you feel when the sun is shining on you is infrared energy. LowE coatings block what is known as near or shortwave infrared. But in addition, LowE coatings are designed to block UV as well.
A quick look at the electromagntic spectrum shows that the visible light spectrum is bordered by the UV spectrum on one side and the infrared spectrum on the other. UV are short waves and infrared are longwaves (I hope this isn't confusing, but I mentioned that LowE blocks "shortwave" infrared - and then I said infrared was longwave energy - hmmmmmmmmmm. The part of the infrared spectrum that the LowE is designed to stop, the part that affects us, is the "shorter" infrared waves. They are still longwave radiation, but "short" for infrared - I KNOW how confusing that is if you are not familiar with it).

LowE coatings block UV and allow visible light thru and then block infrared as well.

On the UV side of the spectrum, we have three "designations" based on the frequency spectrum of the UV:
UVC, which is the really short range stuff (past UVC, you run into microwaves).
UVB, which is the middle range stuff.
UVA, which is the "longwave" UV radiation.

UVC is nasty. At this frequency range the UV is blocked by the atmosphere, especially the ozone layer, but "artifically generated" UVC is also used here on the ground in medical applications to sterilize wounds and to kill bacteria. UVC is used in some swimming pool and hot tub applications (rather than chlorine) to sanitize and to kill bacteria and other organics.
Unfiltered UVC can blind you, and causes burns. Nasty!

The mid range UVB is causes sunburn (and tanning) and is the primary cause of skin cancer.
UVB is also nasty stuff that is mostly blocked by the atmosphere; but enough of it gets thru to the ground to cause a bit of problem. Of course the sun tan crowd would miss UVB, because it is this particular version that causes your skin to brown.

Ordinary glass blocks UVC and UVB. If you are lying in the sun, but under a clear piece of ordinary glass, you will not burn and you will not tan.

Finally, we get UVA. UVA is about 95% of all UV energy that gets to the ground.
UVA does not cause sunburn and it does not cause you to tan. But, UVA goes deep into your skin and causes wrinkles and it also goes into your home and causes your furnishings to fade. There is some controversy about how UVA affects skin cancer...but best to be careful.
Ordinary glass is transparent to UVA. In other words, UVA passes right thru glass.

LowE coatings inhibit UVA. Unfortunately, the fading factor in light does happen to reach into the visible spectrum as well. A tinted LowE coating will help stop even more fading of your furnishings by blocking some of the fading factor in the visible spectrum as well as the UVA.
A good softcoat LoE will decrease fading by about 75% or a bit better.

Laminated glass (which we have not mentioned yet) will protect from fading at something better than 99%....with laminated glass it doesn't matter if you have LowE or tinting - but only for fading. Laminated has no effect on the infrared or any energy advantage.
If you (or anyone) wants to know more about laminated glass, please ask, otherwise I will include no more about it here.

Now we come after-market window films.
Most of the readily available window films are made of Mylar which is a DuPont trade name for a polycarbonate film. Polycarbonates (like most plastics) are inherently unstable when exposed to UV light, so the manufacturer's add a UV retardant into the formula and it makes the film resistant to damge by UV raditaion, but which also makes it a pretty good UV blocker.
I would say to anyone who has windows without a LowE coating and who wants to block UV light, then the addition of a UV blocking film on the inner surface of your windows is not a bad idea.

Hope this helps, Chris.
Please feel free to ask if you have other questions about any of the information that I dropped in this post.

 

Oberon -

Thank you so much for taking the time to reply to this. That was a lengthy post which was well worth the read. I am a technical guy, so I enjoy getting in-depth responses like this one.

My apartment sees quite a bit of sunlight and heats up fairly quick (and it is winter!). I am probably going to get curtains to put on the windows because I have a CRT projection television and the glare makes a mirror out of the TV. The ceilings are vaulted, so it is harder to keep the temperature regulated.

With all of this + my plastic concern, I am interested in doing what I can to help improve energy costs and such in my apt. How much does the UV blocking film run? Do I just roll it out, cut it to match the window panes and stick it on?

Gosh - thanks again for your reply. I just joined the board and was wondering if my message would become one of those "abandoned newbie" threads.

 

CkRtech,

Chris's explaination enlightened me too. (Not sure I followed it all, but at least I'm "enlightened"!!!) LOL!!

As far as "I just joined the board and was wondering if my message would become one of those "abandoned newbie" threads..." Now, that might happen in other sites, but it's never been the case around here. Speaking just for me, and most of the other old timers around here, we ain't prejudiced -- we answer them all!!!

WELCOME!!

 

sorry but I beg to differ. Putting a film coat on the inside of an existing "clear" IG unit can cause heat cracks or make the unit fail. If you want to add a film, do it on the outside.

 

I am not sure I understand. What do you mean "existing 'clear' IG unit?"

I bought some of the Gila Heat Control film and started putting some on my windows today. I didn't see anything on there that said it could potentially cause problems.

 

CkRtech,

Glasman did make a valid point, and one that I failed to address in my earlier post simply because I was thinking in terms of UV protection and not energy efficiency considerations, also I had the impression that you were in a moderate climate.

This is a bit complicated, so I will do my best to explain it clearly.

Every window installed anywhere has a potential for failure due to thermal stress, film or no film, IG or not IG, coated or not coated. Thermal stress in glass is associated with the difference between the temperature in the center of a glass pane versus the temperature of the glass at the edge of the pane. These temperature differences between the edge and the center induce stress into the glass, measured in PSI, and if the difference in temperature induces enough stress the glass will fail. An edge chip, or deep scratch already in the glass can acerbate the problem as well.

As a rule of thumb, 1 degree difference in temperature within the glass area increases stress in the glass by 50psi. Ordinary annealed glass will fail with about 6000psi of induced stress….but, at 2500psi there is an approximate 1% chance of failure due to stress and as the stress level increases, the potential for failure increases as well, exponentially. Note that a 50 degree difference between the center of the lite and the edge is equivalent to 2500psi of thermal stress.
At 3000psi, for example, the chance for failure reaches 10%...and so on. Again, we are talking increased potential and not saying that anything is definite. The statistics are saying that there is an increased risk of failure and NOT that a certain percentage will fail. I hope that that it makes sense how I explained it.
If a window is manufactured using tempered or heat strengthened glass, the potential for a thermal stress failure is virtually zero because of stresses induced during the heat strengthening process are greater than those caused by the temperature variations that the window will actually be subject to in the field..

When using window films, there is an increased potential of the glass in a window failing because the normal thermal stresses are accentuated by the use of the film.
All windows have a temperature variation between the center of the glass and the edge of the glass, but because of the nature of the films, the center of glass temperature can increase at a rate greater than at the edges of the glass – more so than would be normal when not using films. This affects both dual pane and monolithic, or single pane, windows.

Using a clear film causes the least amount of increased variation. The darker the film, the more pronounced the difference. Using a dark film in a very cold climate when the sun is shining brightly can be a problem. The darker film would warm up the center of the glass significantly while the edges of the glass would be subject to a certain amount of thermal conduction where the spacer bar joined the two lites of the dual pane window.
Also, using a film on an IGU or dual pane window that has a LowE coating or on a window with tinted glass may also cause even more problems because they both contribute to additional warmth in the center of the glass.

I will disagree with one thing Glasman said, however. There is no advantage to putting the film on the outside surface of the window versus installing it on the inside. Putting a solar reflective film on the outside of the window would block a certain amount of direct solar radiation, but a dark film would still be prone to heat absorption and the edges of the outer lite would still tend to be colder than the center of the lite. The primary difference would be that the outer lite would now be the one having problems rather than the inner lite.

The original question concerned blocking UV light and also a certain amount of energy savings as well. In my original answer my intent was to offer suggestions for blocking UV energy, and the right film will do so, but there can be a certain amount of risk involved.
I think the risk is minimal, but I apologize for not making that clear in the first post…and while it does happen, these films are used rather extensively all across the country and I might suggest that if window damage caused by applications of the films was really a problem and really widespread, wouldn’t it be more well known?

I hope this helps a bit.

 

Ahh okay.

Well I live in Texas (Houston) - so I rarely see extremely cold temperatures. The weathermen here are saying that it could potentially snow during Christmas, and I will believe it when I see it. I don't think you are going to see much below 30 degrees.

In the summertime, it can get pretty hot. Nothing like Arizona weather - the heat here seems amplified because it is a pretty humid state. It barely ever gets up to 100s, but 80s and 90s are pretty common.

The apartment was built in 1994. I assume that the windows are in pretty good shape and were made well. I didn't see any major "caution" warnings on the product - it is taking me forever to do each pane, so I hope everything goes well because this is taking time!

 

wrong.....
By putting film on the inside of the window, you cause heat build up thus heat cracks in the glass or making the unit fail. If you want to put any kind of film on your window, it should always be on the outside.


This is 1 reason why when you install tented glass, the tent is always on the outside ( keeps it cooler in the summer between panes ) If you install even a tinted ( ie bronze glass or gray glass ) with the tint in, your taking a big chance on a failed unit, or heat crack. I don't care what part of the country you live in, it's the same.

You void your warranty of the window by putting tent on the inside also.

I've been arguing this point with people that install tent for a living for over 20 yrs, and have gone back to houses and offices that had it installed ( on the inside ) replacing the units because it failed or cracked.

Sorry Oberon your dead wrong on this one.

This is something that happened at our shop 1 time.
A coworker put a tinted window on his truck. he went out and did a few small jobs that morning. By noon it was 100 degrees outside. When he got to his job to install the tented window it was broke ( heat cracks ) He asked me what happened when he returned to the shop, saying " I didn't do anything to break it" when I looked at it, it was on the truck clear side out. I told him he put it on the truck backwards , it should have been tent side out, that he got a heat crack.

I understand what your trying to say Oberon, but with having experience with this problem in the past, I think I know what I'm talking about.

 

I don't understand the arrogance, glasman2. You are obviously wrong in this case or are misinformed as to the exact material we are talking about because the stuff that I bought is meant to be installed on the inside. It seems to me the that if the item was not supposed to be installed on the inside, that they would either mention this or have a bunch of lawsuits on their hands.

I mean I came here not knowing anything about this stuff except the fact it existed and was looking for a little advice - but now I have a scientific semi-debate going on and don't know what to believe. lol

 

arrogance? Fine... it's your window, I'll keep my 2 cents out of it.

 

Wait. Wait. Let me rephrase this in the form of a question-

Why would a company release an item that could easily break the glass as you have described? It seems to me the that if the item was not supposed to be installed on the inside, that they would either say it must be installed on the outside or they would have a bunch of lawsuits on their hands.

- Thanks.

 

CkRtech,

I have no idea why the tint mfgr. would tell you to put it on the inside. Like glasman2 said, at the very least it will void the warranty of the window, and there's a good chance that it will indeed cause the glass to crack.

 

Huh. This is interesting.

Well, it isn't really a tint. Well...I guess it is, but it ..

Haha. Here - http://www.gilafilms.com/home/instructions.html

Maybe we are thinking of different things?

 

look at the heat control page. That is what I'm talking about. They prove what I said was true. It says it blocks out %70 of the heat... Now think about this..... heat goes through the outer pane of glass, hits the film on the inside glass and bounces back to the outside glass, Thus building up heat between the 2 pieces of glass. THAT is how you cause heat cracks and seal fail in the unit. I've argued with these stupid tinting people for over 20 yrs. They are out to make a buck just like anyone else. They are hoping that a heat crack doesn't happen and that the unit only fails, so they can say it was the unit , not the tint, when infact it was the tinting that caused it.


Look .... like I said before, it's your window, believe who you want to believe.
I've been glazing since 1977 and ran across this for many yrs. So it's your choice to believe who is lieing.... me or them...I'm not trying to sell you anything, just trying to save you a buck or 2. I wonder if Oberon works for a tinting Co, thus the long "it's ok to use tint on the inside" replies.

 

Hi, glasman2. Merry Christmas, everyone.

Is there glass that is made to withstand the heat? Would the age of the glass (or in other words - when the apartment was built) have anything to do with how well it can withstand the heat?

If there essentially is a "gamble" involved by the film companies when this film is used on glass...I just wonder what my chances are. I wonder what kind of percentage chance I have of the windows cracking.

Is there some sort of alternative form of UV protection? I am on the second story and cannot easily apply an external film to the windows.

What sort of difference would adding curtains over the blinds make? Is UV only a threat when items are in direct sunlight, or do UV rays fill the room and still cause problems?

 

Time out one second.

First, in my first post I recommended a UV blocking film - i.e CLEAR Mylar film - as the best available solution to blocking UV light in this particular instance.

Glasman, if you actually READ my posts you will notice that I NEVER suggested a tinted film, and in fact what I said was putting a film on the outside was not better than putting it on the inside simply because tinted films are not a particularly good idea. I would not suggest a tinted film on the inside or on the outside. As to warranty issues, if the film is inside or outside will not affect the warranty if the window breaks.

Also, I fully agree that tinted glass belongs on the exterior of an IGU, and never on the interior. Please tell me where I suggested tinted glass on the inside of an IGU???

I will go even further and suggest that tinted glass isn't really a very good idea in the first place. Tinted glass, whether on the inside or outside absorbs heat. When tinted glass absorbs heat, the glass warms up and that heat is then radiated...tinted glass will block a certain amount of visible light, but it does very little for energy efficiency, at least when compared with a LowE coating....and as I said, when tinted glass is used it should always be to the outside.

Now a tinted LowE is a totally different thing, and a tinted LowE is actually more efficent than a conventional LowE, but it is DESIGNED to be such.
And, like Lefty said, using a film will void the glass warranty - IF there is a glass breakage warranty in the first place; which is often not the case if they are a generic brand window. And, you will also find that using so-called insulated curtains may also void glass breakage warranties.

Also, glasman mentioned the possibility of seal failure due to increased heat inside the IGU. I know of several studies that do support that possibility with one particular spacer system, but I very much doubt that your windows use that particular system. The three most widely used spacer systems in North America do not have a warranty exemption for seal failure when using films. The manufacturers are comfortable that their seal systems will not fail due to possible excess heat build up. However, the largest of the three, Cardinal IG, does have a warranty exemption for glass breakage if you are using a film. The other two do not because of manufacturing differences. Cardinal makes completed IG's for sale to various window companies. The other two systems - Intercept and Super Spacer - sell the spacer materials to the window companies to make their own IG's in house.

Glass can break due to heat stress whether you use a film or not.
Window companies know this and the warranty issues in relation to using films and other "insulation" products with windows affect primarily warranties because there is no way to tell once the glass breaks if it was caused by the use of the film or whether it was a spontaneous break. The glass companies know that there is an increased occurance of heat stress breakage when using films, but they also know that that sort of breakage is not exclusive to using films. They also know that heat stress breakage is more likely when the glass edge is flawed. As I mentioned in an earlier post, the POSSIBILITY of a higher occurance of heat stress breakage does increase with the use of an after market film. And, IF a pane of glass in a window has a flawed edge, that possibility increases even more. An edge flaw that might not have caused a problem otherwise, CAN break when exposed to the aditional stress of a heat film, insulated curtain, or other "energy saving" ad on.

CkRtech, you asked if there is glass made to withstand breakage due to heat stress - yep, there is. I mentioned earlier that both tempered and heat strengthened glass will withstand heat stress and if someone wants to use the most darkly tinted film they can find with tempered, go ahead, because you won't break the glass. Also, thinner glass is more prone to heat related stress fractures than is thicker glass. Also, if the IGU uses an aluminum spacer between the panes there is an increased risk of stress cracks.

Some window manufactures use heat strengthened glass in certain of their
units because it allows them to use a thinner glass without risk of breakage due to heat stress. Thinner glass is used for several manufacturing reasons, but one advantage relates to the width of the space between the glass panes in an IGU.

Finally, while I may disagree with ideas, but when I do so I READ what the other person has actually said and at least try to understand what the other person is saying before I attack them and call them a liar. In fact, I never have said someone else is a liar because they had an opinion different than mine.

Glasman, as to your suggestion that I work for a tint manufacturer, I don't. As a matter of fact, I work in the glass industry in a research and development area, involved with certification, testing, and analysis of new products and procedures. I have worked very closely with product development and research folks of some 35 window companies over the past 14 years that I have been doing this.

Glasman, I have enjoyed reading your posts since I came to this site, and 99% of the time I totally agreed with what you said on those replies. I think that you give very good advice.
I also understand that your initial concern on this thread was for CkRtech and the possibility that he was making a mistake using a film. But, my whole point was to offer an idea, a possible suggestion for a UV problem. I should have mentioned more about the risks associated with using a film in my first post, but I tend to make very long and technical inputs and my first post was rather long and technical already. I really like to explain all options and also WHY something is someway and not simply to give my thoughts and no reasons for them; and to be honest, it simply never occured to me on the first post to mention possible risks due to film use...although it should have and I did apologize to CkRtech for that oversite. Again, I was NOT thinking of a tinted film, simply a clear mylar for UV protection.

Agree with me or disagree with me, I don't care, but don't ever call me a liar and don't ever accuse me of trying to suggest something to someone because there is ultimately some sort of gain in it for me.

And, as usual this thing is longer than hell.

 

CKRtech
Oberon

glasman2

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