Green Glue walls, and glass thickness

After reading Rod's book and researching here for a while I understand the equation of 1/3rd thickness of gypsum wall to figure out glass thickness for a studio window. I'm wondering how green glue changes the equation (if it does). For instance my instrument rooms have 2 layers 5/8 plus 1/2 homosote all with green glue between (2 gg layers). The other side of that wall has 1 layer 5/8 with 1 layer homo with green glue in between. I can easily and quickly buy laminated glass up to 1/2 inch thick, but once I get to 5/8 inch glass I run into a 4-8 week wait and a $75 crating charge. Plus the glass is much more expensive ($100 per sheet per 1/8 inch thicker). I will do one side 1/2 for temporary purposes and wait for the 5/8 or even 3/4 for the other side of the window if I have to, but if 1/2 inch and 3/8 inch glass will do the trick I would rather save the time and money. Of course, I don't want to go 99 yards and kick a field goal either. thoughts?

Answering what I think your question is, Homasote does not significant improvements in isolation. If you calculate on the drywall layers, 1/2" glass will be fine. Transparently, Andre

8) as Andre points out, the homasote probably doesn't do much but the green glue will add quite a bit to the equation since it is not a glue as its name implies, but rather a viscous constraint layer damping mechanism - it never really hardens and allows the two layers of drywall to move independently while being dampened. don't put the green glue between the homasote and the drywall, but between 2 drywall layers.

Thanks for the help guys, The walls are already built, I know what green glue (hopefully) does and what the homosote does etc, I'm just curious about how it changes the formula for glass thickness. I read another poster here that said green glue effectively doubles your wall mass. So for the double 5/8 wall that would have an effective mass of a 2.5 inch wall, and the other wall would have an effective mass of 1.25 inches. Seems far fetched to me, and in that case to match the wall I would need about a 7/8 piece of glass and about a 1/2 piece of glass. A 7/8 inch piece of laminate glass seems nuts (and expensive). I'm interested how other people with green glue walls approached this.

Actualsizeaudio wrote:

I read another poster here that said green glue effectively doubles your wall mass. So for the double 5/8 wall that would have an effective mass of a 2.5 inch wall, and the other wall would have an effective mass of 1.25 inches. Seems far fetched to me, and in that case to match the wall I would need about a 7/8 piece of glass and about a 1/2 piece of glass. A 7/8 inch piece of laminate glass seems nuts (and expensive).

Asa, you should read the book again - especially the pages on glass....... The thicknesses you're quoting are corrct for annealed (not lami) glass......... for laminated glass I generally thin out the glass by 1/3 or so - 3/4" would be 1/2" = And I agree with the idea of double sheets of 5/8 GDW wit green glue would be about equivilent with 4 layers of 5/8" alone. Rod

Thanks Rod! I missed the part in the book about lami glass not needing to be as thick as other types of glass. I did look again and didn't see anything on matching green glue walls.....so thanks for the clarification on that. So you think 1/2 inch lami glass and 3/8 lami glass will suffice? That is good news for sure! I just need to make sure my supplier really is getting me laminated glass. Also, does a pice of laminated glass need to be tempered if it is installed in a door, or does the sandwich in between the 2 layers of a laminated piece of glass make it shatter proof? Thanks again.

Actualsizeaudio wrote:

Also, does a pice of laminated glass need to be tempered if it is installed in a door, or does the sandwich in between the 2 layers of a laminated piece of glass make it shatter proof?

Asa, it is not phyaically possible to temper lami glass......... Laminated glass is already a safety plate - which is why it's used to make auto windshields (whereas the remainder og the glass in an auto is made from tempered glass). You should check with your local building official to verify what they will require to prove the indentity of the glazing in the door - some might accept a manufacturer's certificate certifying that they processed that particular glass for that particular door opening - and the tracking of ownership (manufacturer to wholesaler to retailer to your project) in order to meet the code. Other's might require the acid etching similar to what you see on typical windows in door openings. On another note - make sure that you require the acid etching for tempered glass if using it people - it is not always automatic for the maufacturer to put that on a piece of tempered glass - and it is specifically required where tempered glass is used in a required safety plate. BTW, sure I gave you the info on the green glue - there is a greaph in thr book in that section that indicates performance for green glue and standard wall construction up through 4 sheets...... besides which - I explained that you can extrapolate and comple pretty close to on the money if you just use mass law calculations........... Sincrely, Rod

Actualsizeaudio wrote:

Also, does a pice of laminated glass need to be tempered if it is installed in a door, or does the sandwich in between the 2 layers of a laminated piece of glass make it shatter proof?

Asa, it is not phyaically possible to temper lami glass......... Laminated glass is already a safety plate - which is why it's used to make auto windshields (whereas the remainder og the glass in an auto is made from tempered glass). You should check with your local building official to verify what they will require to prove the indentity of the glazing in the door - some might accept a manufacturer's certificate certifying that they processed that particular glass for that particular door opening - and the tracking of ownership (manufacturer to wholesaler to retailer to your project) in order to meet the code. Other's might require the acid etching similar to what you see on typical windows in door openings. On another note - make sure that you require the acid etching for tempered glass if using it people - it is not always automatic for the maufacturer to put that on a piece of tempered glass - and it is specifically required where tempered glass is used in a required safety plate. BTW, sure I gave you the info on the green glue - there is a greaph in thr book in that section that indicates performance for green glue and standard wall construction up through 4 sheets...... besides which - I explained that you can extrapolate and comple pretty close to on the money if you just use mass law calculations........... Sincrely, Rod

rod gervais wrote:

Actualsizeaudio wrote:

Also, does a pice of laminated glass need to be tempered if it is installed in a door, or does the sandwich in between the 2 layers of a laminated piece of glass make it shatter proof?

Asa, it is not phyaically possible to temper lami glass......... Laminated glass is already a safety plate - which is why it's used to make auto windshields (whereas the remainder og the glass in an auto is made from tempered glass).

Rod, It's correct that you can't temper laminated glass (that foil should just burn away causing whatever effects). Hence one uses tempered glass which is then laminated. But there is laminated glass made from standard floatglass as well. I think it's even more standard. In car's one uses both safeties. Warm regards Eric

Eric_Desart wrote:

It's correct that you can't temper laminated glass (that foil should just burn away causing whatever effects). Hence one uses tempered glass which is then laminated. But there is laminated glass made from standard floatglass as well. I think it's even more standard. In car's one uses both safeties. Warm regards Eric

Eric, until now I was not aware of the fact that yopu could manufacture lami glass using tempered materials....... Thanks for the education. Rod

Rod, Thanks again, and happy Easter. I'm going to call my building official tomorrow and ask him about what he needs to see in regards to the glass I'm putting in the door. I'm thinking my receipt for laminated glass will suffice. When he came to inspect the framing of my house he never even pulled out his tape measure. He is, to put it mildly, laid back (and reasonable). I'm going to check first to make sure though. If I understand Eric, the laminated glass can be made with glass that is first tempered before it is glued together. Would there be any advantage to this for a door window? From reading the glass section of the book it seems clear to me that lami glass is all you need for safety reasons. I just want to make sure it doesn't need to be lami glass made with tempered glass pieces. I'll also ask my glass supplier if this is something they do. I'll post my findings tomorrow. Also, I'm not trying to be argumentative, just helpful. I re-read the glass section of the book and it does not mention the 1/3rd reduction in glass thickness for the lami glass. It talks about the benefit of laminate in controlling transmission around the critical frequency range vs. float glass, but not that a 1/2" lami = 3/4 float in transmission loss. I apologize if I'm still missing it.

Rod, You're welcome ..... For one or the other reason I missed a past post (in some heated thread I disagreed with you and vice versa) in which you stated that we weren' t bashing, but you considered me a friend. My not replying there could be wrongly interpreted as I kept my distance from that comment. I consider you a friend as well, always did. That doesn't mean we always should have to agree.

Actualsizeaudio wrote:

If I understand Eric, the laminated glass can be made with glass that is first tempered before it is glued together. Would there be any advantage to this for a door window? From reading the glass section of the book it seems clear to me that lami glass is all you need for safety reasons. I just want to make sure it doesn't need to be lami glass made with tempered glass pieces.

To temper glass one need to heathen it. This PVB foil couldn't withstand this temperature, hence you understood right: http://en.wikipedia.org/wiki/Toughened_glass Last year I did a studio where standard laminated glass was used for the normal windows, but laminated tempered glass was used for 100% glassdoors without wooden (or whatever frame). Laminated glass, keeps all peaces together, when glass breaks. This extremely thin foil is unbelievably strong. In fact laminated glass was designed for the safety world. The acoustics proved a useful side effect. Tempered glass is better impact resistant (small stones or whatever flying against the screen of your car window). Tempered glass when it breaks (if it happens as supposed to) breaks in a million pieces without these very sharp edges typical for standard glass acting as knives when it breaks. Tempered glass is also used for doors or whatever where the hinges and other accessories are directly mounted on the glass. It's a matter of money: Combining both properties is expensive, and these panes have to be made on size in the factory because you can't cut them afterwards (grinding could possibly be an option, anyhow it's expensive). Standard laminated glass (2 layers of glass) can still be cut with standard means (is difficult, you have to cut it in both sides, hence it asks some practice). Such panes are produced in large sizes. For normal situations (unless you have an enormous amount of people passing through) standard laminated glass will do. If you have such a 100 % glass door, you better use it tempered to mount these accessories on/through that glass. Acoustically there is no significant difference. Hence the choice is mechanical or increased impact resistance. I'm just speaking of my own experience. I've no idea what standards worldwide have to say about all this. :) If you have unlimited budgets you can go for the best. But whether that's sensible is a very open question mark. Note that in laminated glass there are differences. The last +/- 15 years (can't remember exactly) there are special versions of laminated glass where the foil is specific designed for acoustic purposes. But the effect is mainly to be found in the coincidence area. Hence it has mainly sense when you go to thick panes where this coincidence falls within a dominant/defining frequency range. Stadip silence from Saint-Gobain is such a type (rouglhy price ca 135% of normal laminated, but depends)

Eric_Desart wrote:

Rod, You're welcome ..... For one or the other reason I missed a past post (in some heated thread I disagreed with you and vice versa) in which you stated that we weren' t bashing, but you considered me a friend. My not replying there could be wrongly interpreted as I kept my distance from that comment. I consider you a friend as well, always did. That doesn't mean we always should have to agree.

Eric, don't worry - I only took it to mean that you had moved on to another thread somewhere (damn if you could figure out how to charge a fee, someone could make a decent living here - certainly keep busy enough). Anyway - as always tis nice to "see you" again....... I hope life is treating you well. Sincerely, Rod

rod gervais wrote:

Actualsizeaudio wrote:

I read another poster here that said green glue effectively doubles your wall mass. So for the double 5/8 wall that would have an effective mass of a 2.5 inch wall, and the other wall would have an effective mass of 1.25 inches. Seems far fetched to me, and in that case to match the wall I would need about a 7/8 piece of glass and about a 1/2 piece of glass. A 7/8 inch piece of laminate glass seems nuts (and expensive).

Asa, you should read the book again - especially the pages on glass....... The thicknesses you're quoting are corrct for annealed (not lami) glass......... for laminated glass I generally thin out the glass by 1/3 or so - 3/4" would be 1/2" = And I agree with the idea of double sheets of 5/8 GDW wit green glue would be about equivilent with 4 layers of 5/8" alone. Rod

The Green Glue site says laminate glass loses its advantage (via a vis sound isolation) in cold weather. I am trying to get specs for an external window. If you want all the gory details I have plans posted under "Berkeley Garage ..." So - my question - I will have an external wall of 1/2" CDX ply and 7/8" stucco applied as siding. Does it seem that 3/4 " tempered glass should match that wall? (Gervais in his book prefers tempered glass to float, but as this lengthy post indicates there's also laminate glass options). Keep reading. It gets worse. I have been planning for a 4 x 5 foot window ...external window, I mean. To allow light into my room-within-a-room assembly. As the writer of this post notes, things get a bit crazy in terms of availability & price when you get into glass 3/4 " and more thick. So, what do you think of this ? Anybody out there who's done something like this? My concern, if it's not obvious, is that I don't want to undermine the benefits of building a room-within-a-room using double ply and Green Glue. That (internal) room needs its window & the external wall needs its window.

I will have an external wall of 1/2" CDX ply and 7/8" stucco applied as siding. Does it seem that 3/4 " tempered glass should match that wall?

A good match would be 1/2". Andre

Thanks for the clarification.

Folks, I do prefer tempered glass to float - and also to laminated glass. My only reason for this is due to the fact that you can scratch or pit float and standard laminated glass - while this is not the case with tempered. With tempered - either it is unmarred - or it is broken - it's just that simple. I think I shall revisit this issue and make it a one of chapters I expand when I prepare to publish the 2nd edition of the book. Sincerely, Rod

rod gervais wrote:

You can scratch or pit float and standard laminated glass - while this is not the case with tempered. With tempered - either it is unmarred - or it is broken - it's just that simple. Rod

I don't believe that's correct Rod 8) I bought some large sheets of tempered glass on eBay last year, 15mm thick. My pal, who happens to be a gardener, helped me collect with the aid of his van. Which had loads of garden cuttings in the back. We didn't bother wrapping the glass, and just laid it out on the large 'cushion' of twigs and thin branches. The journey home was rather noisy, *screech screech* When we got home, the perfect pane of glass was covered in unsightly scratches :cry: Some areas were ok, but it will transpire that my 3-years-in-the-planning-but-not-yet-off-the-ground studio will have scratched windows :x I'm gonna have to bury part of the glass in the walls to hide the worst of it. :x From what I remember reading on a construction forum somewhere, tempered glass is actually easier to scratch as the surface is slightly softer than regular stuff, even though the inner core is much much stronger.

Deluks wrote:

rod gervais wrote:

You can scratch or pit float and standard laminated glass - while this is not the case with tempered. With tempered - either it is unmarred - or it is broken - it's just that simple. Rod

I don't believe that's correct Rod 8) I bought some large sheets of tempered glass on eBay last year, 15mm thick. My pal, who happens to be a gardener, helped me collect with the aid of his van. Which had loads of garden cuttings in the back. We didn't bother wrapping the glass, and just laid it out on the large 'cushion' of twigs and thin branches. The journey home was rather noisy, *screech screech* When we got home, the perfect pane of glass was covered in unsightly scratches :cry: Some areas were ok, but it will transpire that my 3-years-in-the-planning-but-not-yet-off-the-ground studio will have scratched windows :x I'm gonna have to bury part of the glass in the walls to hide the worst of it. :x From what I remember reading on a construction forum somewhere, tempered glass is actually easier to scratch as the surface is slightly softer than regular stuff, even though the inner core is much much stronger.

I believe you were informed incorrectly. According to the IWCA (International Window Cleaning Association) if your tempered glass develops scratches - that is most proably due to a microscopic defect called fabricating debris. Especially if the scratches were caused by tigs and branches (which are MUCH softer than glass itself). Do the scratches appear to have a definate beginning? Does the scratch look something like a comet? Rod