Replies

1. 
   Oak River Mike | Jun 13, 2009 08:22pm | #1

   I have that issue as well as I had just looked through it for something else about two days ago.

   I guess it depends on how "special" the size needs to be as to get either low E or tempered glass for a site built unit and mount it all properly could be a challenge in time.  I would prefer to pay extra for a factory built unit for the peace of mind to avoid call backs.

   But thats just me.

2. 
   Pelipeth | Jun 13, 2009 09:59pm | #2

   I did one many years ago using a patio door section 1/2 of an Anderson 6'0x6'8.

3. 
   WayneL5 | Jun 14, 2009 01:01am | #3

   The glass has to be tempered.  Using anything else would be against code and dangerous.

1. 
   oberon476 | Jun 14, 2009 03:42am | #4

   ...or laminated would be acceptable as well. 

    

1. 
   Dreamcatcher | Jun 15, 2009 02:27pm | #5

   .....wired too.

1. 
   oberon476 | Jun 16, 2009 03:02pm | #7

   Wired is tricky...

   It has never been a safety product, but it was exempted from safety codes because  it did a good job of staying in place during a fire. 

   Unfortunately, a number of people have been seriously hurt (a few killed) when having close encounters with wired glass over the years and many codes no longer allow wired glass to be used in any application (always with the odd exception of course).

   You may see wired glass in some older skylights, but not in any newer ones.

   Personally, I wouldn't want to be standing under the stuff.

    

    

1. 
   Dreamcatcher | Jun 16, 2009 03:40pm | #8

   I only mentioned wired because I saw recently in a book ["Concrete at Home" by Cheng / Taunton Press / pg. 111] and was curious about the legalities with it so I looked it up and it appeared to be acceptable. I see wired used here and there in other applications, mostly doors, sidelights, and transoms... you say not allowed in ANY application though. What are some examples of where it is and isn't allowed?DC

2. 
   oberon476 | Jun 17, 2009 04:09am | #9

   ANSI-Z97.1-2004, along with CPSC 16CFR1201, are the "bible" of basic safety glass application.The ANSI lists two classifications of safety glass - Class A for applications greater than 9 ft² and Class B for applications less than 9 ft².  In addition, it lists class C specifically for wired glass applications - and (as I recall) it does state that that wired glass is not considered to be a safety product.  Technically, ANSI Z97 only applies to doors and 16CFR1201 applies to windows, shower doors, oven doors, skylights, and pretty much anywhere else glass may be used; and while the ANSI does address wired glass specifically, that was a change that came in with the 2004 update.  The 1984 version did not have the special category.  The 16CFR1201 hasn't been updated for a good long time (20 years??) and to be honest I don't recall off-the-top-of-my-head the specifics of wired glass - but I know that it is addressed in there.  Wired glass is not as strong as ordinary annealed glass.  While the wires help the glass stay together if the glass is broken, the imbedded wires also weaken the glass as well.  When someone puts an arm or a leg, or a head into the stuff it breaks fairly easily and the appendage goes thru it.  Unfortunately, the glass remains in the frame due to the wires in the glass and someone has the possibilty of having a very serious injury - potentially worse than it would be if the glass had simply failed. But, that same glass does a good job of staying in place in case of a fire, so it is still used extensively for that application.IRC section 608 addresses the use of glazing products in overhead applications - skylights, green houses, sun rooms, etc. and as I recall (again without looking it up) that the IRC has no specific restrictions against using wired glass in that particular application.Wired glass usage really is dependent on local codes.  Some localities have virtually no restrictions while others don't allow its use at all.  I admit to a definite prejudice against the stuff in most applications - it isn't safety glass and it really is a product that kind of fell in between different codes simply because it does have a specific application where it works as required and sometimes that use conflicts with other code requirements. 

   Edited 6/17/2009 7:02 am ET by Oberon

3. 
   Dreamcatcher | Jun 17, 2009 05:11pm | #10

   Oberon,Thanks for all the information. You work in the glass research industry?What's new and exciting there?DC

4. 
   oberon476 | Jun 18, 2009 02:16pm | #11

   Yep, I do.

   I used to be a lot more hands-on, but now it seems that I spend way more time chained to a computer than I do actually getting involved with the fun stuff.

   What's new?  I would say that triple panes in various applications is getting a lot of attention with the new energy star requirements coming on line. 

   The newest, latest, most current, final version of energy star does include a trade-off between solar heat gain and U-factor for folks in the far north.  I would suggest that that change has some folks looking at some of their products.

5. 
   Dreamcatcher | Jun 18, 2009 07:20pm | #12

   I have been hearing a lot about the new triple pane windows; from my vantage point I half expect to see a "pane war" similar to what goes on in the razor market (I think they are up to 5 blades now). Nevertheless, I like the fact that energy star ratings are applied and that the gov is helping to get the word out.As far as trade-offs with heat gain and U-factor; I am no thermal engineer but when I bought windows for my house, I made the decision to not use Low-E glass against the recommendation of the window salesman. Although I don't claim to be an expert on glazing, from what I could tell I was not gaining enough insulating capabilities for what I would be loosing in winter heat gain for the price of the up charge. You see, I tried to PROPERLY design my windows to maximize efficiency based on their size, style, and placement. Whereas I see so many homes that just fill walls with glass, I used specifically placed but generally smaller awning, casement, and DH windows to catch heat in winter or cross ventilate in summer....or in other words maximize winter heat gain and not worry about loosing conditioned air in summer. Again, I am not an engineer but so far I have found that my decisions are working as expected. What is your opinion on low-e? DC

6. 
   oberon476 | Jun 19, 2009 05:18am | #15

   My son gave me one of those five blade razors - and I admit it gives an amazingly close and comfortable shave. But the replacement blades are freaking expensive at about $4.00 each. Still they last a long time and I think they are worth it. Unfortunately, I can't agree with your decision to install windows without LowE coating. Simply, a window with LowE coated glass will always outperform a window without LowE glass - no matter what the environment (north, south, hot, cold) where the window is installed. Dpending on climate and coating, the difference could be significant.LowE coatings affect glass performance both summer and winter. While the R-value difference between a dual pane clear glass window and a dual pane window with a LowE coating may not seem like that much, R-value only accounts for conductive gain or loss.And, that doesn't account for the 60% of heat gain and heat loss thru a window as radiant energy. LowE coatings do affect conductive thermal transfer, but much more so they affect radiant heat transfer.Consider winter conditions with ΔT at 70°F (0F outside and 70F inside). A clear dual pane IG is going to lose 13 Btu/hr/ft² to conductive heat loss. But the same IG is going to lose 21 Btu/hr/ft² radiant heat. The center-of-glass temperature of that IG unit is going to be 43°F - which can be an important consideration as well.A dual pane with a LowE3 coating (I use LowE3 because it is becoming a standard offering for many window companies in order to comply with the .30/.30 requirement of the $1500 tax credit), will have conductive heat transfer of 16 Btu/hr/ft². If you read back you might notice that the conductive heat transfer using clear/clear dual pane was 13 Btu/hr/ft²...the LowE coating actually increased conductive heat loss in this example, which is likely to surprise most folks, I suspect.However, the same IG with LowE3 coated glass is going to lose 1 Btu/hr/ft² in radiant heat versus 21 Btu/hr/ft² loss for the clear glass dual pane. The coated window blocks literally 20 times the radiant heat loss of the uncoated glass.So as a direct comparison a clear dual pane IG loses literally twice as much heat as does a LowE3 coated IG in this scenario.And the inside surface temperature of the glass is 56°F or 12° warmer than the uncoated glass. This increased glass surface temperature will affect the comfort level in the room (and potentially thermostat setting), as well it may also affect both convection currents resulting from a cooler glass surface (again affecting room comfort level) and condensation resistance on the window surface.In the summer, the same conditions apply, but obviously in reverse. At 90° outside and 75° inside, a dual pane IG will pass just about 186 Btu/hr/ft² into the home while in direct sunlight. A LowE3 coated IG will pass 66 Btu/hr/ft² in identical conditions.

4. 
   JeffinPA | Jun 16, 2009 04:40am | #6

   I'll install any skylight anywhere so long as it is a Velux.

   Never had a leak in one!

   Seen lots of others leak bad.  (both installation issues and manufacturer issues)

   Velux with their flashing kit is cats meow.

   I would custom order if I had to but would not go another route.

   That is just me.  I dont like roof penetrations and not willing to take the risk for a warranty call back on something I have no business messing with.

    

   Just my opinion obviously.

1. 
   cic317 | Jun 19, 2009 12:07am | #13

   I second for a Velux unit, Been using their electric venting unit for a few years REAL HAPPY w/ them. We have installed a few on flat roofs, usually build up 8" curbs pitch the top & used a torch applied roofing or modfied SBS to the curbs, never any problems.The same holds for pitched roofs, they have a real nice flashing system,add some ice shield under & your good to go!

1. 
   gusfhb | Jun 19, 2009 04:07am | #14

   Using a more energy efficient glass was my issue, skylights lose a tone of heat, and the velux have only a pretty standard glass.My thinking is that if I am already building the curb for the low pitch roof, why not just keep going....

5. 
   Hudson Valley Carpenter | Jun 19, 2009 06:37pm | #16

   I'll just add that many of the experimental skylights I've seen have been notorious leakers, including one of mine.  It was my first...and last. 

   So give the HO a five gallon bucket when you leave and expect to return, more than once. 

   Or call a couple of glass shops and ask their service rep how often they get calls to fix leaky experimental skylights.

   Not sayin' it can't be done successfully, just that the potential for problems is high.

   
   

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   Edited 6/19/2009 11:41 am by Hudson Valley Carpenter