Would IGU windows using laminated glass be the preferred choice to eliminate UV?
I am considering the use of an Insulating Glass unit (IGU) using laminated glass. I assume the laminated glass will be on the interior side. I live in Seattle so air conditioning is needed only 3 months/year. I want low U-factor and high light transmittance (70% is ideal). Also want to kill UV as much as possible. Laminated glass will kill 99% of the UV while some LoE coatings can give 95% but reduces the transmittance to 66%.
Here is a possible configuration using Cardinal Glass:
a) Outboad lite is 3mm glass with LoE270 on surface #2 (and perhaps LoE-x89 on surface #1)
Not user if this needs to be increased in thickness to match the thickness of the laminated glass.
b) Air space: 1/2″ filled with Argon
c) Lamainated glass = 2.7 mm glass + 0.03″ PVB + 2.7 mm glass
with inboard surface (#6) coated with LoE i89 preferably.
d) Spacer System: Endur IG
My understanding is that laminated glass can deteriorate which is why the max warranty is only 5 years. Nevertheless, laminated glass with modern PVB and construction methods seem to have solved most of the delam issues.
Pros:
1) Kills UV and has good U-factor. Not sure what the transmittance is. Trying to find out.
Cons:
1) Warranty only 5 years instead of 20 years w/o delaminated glass.
2) extra cost
3) IGU thickness is greater.
So the trade becomes light transmitance vs UV protection.
Any insights or recommendations appreciated.
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Replies
since 270 and i89 give a VT of 69 percent, I cannot see how the laminated can be above that
I think with a COG U value of .20 the 270/i89 is pretty good for the VT
for the UV 366/i89 seems to be the killer combo , 63% VT, 5%UV and .2 COG U value
It is my thinking you are overstressing VT, you will not see the difference in small differences.
Lower Vt glass starts to be a little more mirror like, meaning at dusk you start seeing your reflection sooner.
unless there is a piece of clear glass next to it you will not notice
http://www.cardinalcorp.com/source/pdf/Technical_Glass_Guide_Web.pdf
Thanks
I know that laminated glass kills 99% of UV all by itself. I'm just trying to get it into the IGU without much loss of VT. Otherwise, the LoE366/i89 is the answer.
I'm happy with the 270/i89 combo but thought having laminated glass instead of a clear inner lite I could kill the UT to 99% w/o much hit on VT.
I have no VT numbers with the laminated glass so I looked at VT reductions for 3 pane glass. It appeared to me that adding one more 1/8" lite (as the laminated glass would require) the VT only drops by .03 ( say from 0.69 to 0.66, but I'm guessing here). If so, have the same VT as LoE366 but now kill 99% UV.
I wish I had a program that would allow me to calculate the VT for the IGU with LoE270 and laminated glass.
plastic is not as clear as glass
http://www.commercialwindows.org/laminates.php
single laminated pane .84
if a clear pane is .9 then a clear then laminated out be about .75
your specified glass would probably be 58% vt [.85x.69]
all this for 4 percent on UV?
Is the Mona Lisa on the other side of the window?
Point taken.
But just adding films to widows kills UV by 99%. The bad news here, however, is that it can cause the IGU to fail. So I thought laminated windows could solve this problem.
The real issue is that I have no real handle on how much UV reduction is necessary. 95% reduction probably is adequate but 99% is certainly better. So, does this 4% save my carpets, floors, and furniture from fading sooner? It will of course, but is it just a few extra years?
Will see if I can find some data on this.
Thanks again.
BTW, unless I can get to 99% UV reduction, I will need to return the Mona Lisa to Paris. Oh well.
What I was trying to point out is that you can usually get one thing that is important to you, but then you start to make tradeoffs.
If a couch fades in 5 years in front of a clear glass window, how long before it fades in front of a 95 percent window? 50 years? and what would be the improvement at 99 percent? How long do you keep your couches?
Personally I am a fan of overhangs, which also help water control, which seems a bigger deal in Seattle.
Plus by the time the carpet fades, you wanted a new carpet anyway.................
What about Alpen windows that use a suspended plastic film for the middle pane(s)? That might be a way to get the UV blocking at little to no added cost.
Response to Charlie SULLIVAN (Comment #6)
I’m glad to see an engineering solution exists to reduce UV by 99% or more other than laminated glass. The thermal and optical numbers for the Alpen 525-S series appear to be a good fit for me in Seattle. For a low profile picture window, the Alpenglass 5H has 99.9% reduction on UV and has the following values.
U-Factor: 0.17; SGHC: 0.48; VT: 0.62; CRF (condensation resistance): 68
See: http://thinkalpen.com/wp-content/uploads/2014/02/525-S-Series-Datasheet-20140203-web.pdf
On Comments #4 and #5
In addition to VT, it appears I’m overemphasizing UV protection as well. See:
http://www.showcasewindows.com/wp-content/uploads/2015/03/Shedding-New-Light-on-UV-and-Fading.pdf
This data shows that even with 100% reduction of UV, fading will still occur due to light in the visible range. Moreover, Low E coatings are important to reduce fading in the visible range.
So, what does this all mean to me?
UV reduction is certainly important but overall reduction to fading also requires a good low E coating on an IGU. It appears, to properly assess fading, the Tdw-ISO number needs to calculated and evaluated.