Skylights? Or stick with windows?

I am planning room-within-room assembly of the sort described in Rod Gervais' book on the topic. You can find a thorough layout of my scheme if you to "Berkeley Garage..." I will be using 2 layers of rock for the internal space with Green Glue between the layers. A friend in Albany, Ca. did a similar job a few years ago & got a great result. My question: I am trying to decide between windows and skylights. Unlike many studio designs, I want to get some light in from the outside world! Do you know of a good source of info as to best means of construction for SKYLIGHTS with a room-within-room assembly. Gervais' book does not address this (though he has plans for windows). This site & acoustics.com similarly have little info on builiding skylights while maintaining isolation. Just I was close to a decision on windows, a fellow on acoustics.com suggested my worries about isolation would be minimized if I went with a skylight instead. Is this true? I'm going to have an 8 foot internal ceiling, then a vaulted roof above. I cannot imagine how to create a skylight without connecting the two structures in an undesirable way, unless I have skylight / airspace / skylight, with no enclosed conduit for the light. And that sounds like a dim solution, if you'll pardon the pun. Does anyone else out there have good things to say about skylights? Could you guide me to some plans for building a skylight with sound isolation qualities?

Skylights are windows on their side. Same principles. Just have a break in the tunnel to prevent flanking. Andre

AVare wrote:

Skylights are windows on their side. Same principles. Just have a break in the tunnel to prevent flanking. Andre

Hi, Andre - Thanks. Duly noted about the break in the tunnel. Someone over at recording.org posted this: "If you use a skylight any noise you transmit will go up, annoying only birds." Would you agree? It sounds from your post that you take another view: You consider skylights & windows more or less equal, and that I should base my decision on aesthetics. I'm thinking there are some structural considerations, here. If I hack through two layers of 5/8" sheetrock & Green Glue to put in a skylight in the ceiling of my internal assembly, that window needs to have at least 1/2 " of glass, preferably laminate, according to what I've been hearing. That's a hell of a heavy window to install in one's ceiling. Has anyone out there done this?

quiet wrote:

Someone over at recording.org posted this: "If you use a skylight any noise you transmit will go up, annoying only birds."

Do you have airplanes, helicopters, rain showers, and/or thunderstorms above your roof? Do your neighbours not care about low frequency noise from your music? If you are near a freeway, truck route, and/or train tracs, do they in your neighborhood make no low frequency noise?

I'm thinking there are some structural considerations, here. If I hack through two layers of 5/8" sheetrock & Green Glue to put in a skylight in the ceiling of my internal assembly, that window needs to have at least 1/2 " of glass, preferably laminate, according to what I've been hearing. That's a hell of a heavy window to install in one's ceiling.

The thickness of the glass is based on having the same mass as the partition material it is replacing. The glass weighs the same as the drywall. Andre

The thickness of the glass is based on having the same mass as the partition material it is replacing. The glass weighs the same as the drywall. Andre

From Wikipedia (just to make sure we're using words the same way): "In everyday usage, mass is more commonly referred to as weight." I'm trying to square your statement with this post from another Forum user:

The general rule of thumb around here, is to use glass 1/3 the thickness of your plasterboard walls. That's based purely on mass, with the density of glass being roughly 3 times that of plasterboard. Using Green Glue changes that relationship in favour of the plasterboard, especially for lower frequencies. You'll have to make a judgement call on that yourself, and price will certainly be a factor at those thicknesses! You'll probably want to have a look at the Knightfly's handy Material Densities post.

Unfortunately, the Knightfly post does not give specs for glass. I keep running into the advice to use glass 1/3 the thickness of my sheetrock (the fellow posting above says plasterboard, but I assume we dealing with semantics again, here). Are we all in agreement that that glass 1/3 the thickness of the sheetrock is an effective guideline -- rounding up, if one is using Green Glue? And what sort of glass are we talking about. Rod Gervais book lists glass in ascending order of effectiveness as: float, tempered, laminate. Final note (maybe not everyone knows this?): The Green Glue website says laminate glass loses its superior abilities in cold weather, though it is not specific about temperature.

quiet, Kinda' like I said over in another forum... The mass of an opening "should" be equal to or greater than that of the rest of the surrounding surface. A rule of thumb is just a general rule. Anything specific should be checked and verified with measurements and calculations. Just because someone says that a piece of glass should be 1/3 the thickness of the wall, doesn't literally mean just the thickness of the gypsum. It really means the density of the wall as a system... trifling again... but a potentially HUGE difference. Case in point... a wall that is of 2x4 construction with 2 layers of gypsum (with or without green glue) would require the same thickness of glass as a 2x8 stud wall with 3/4" MDF and 2 layers of gypsum with green glue? Not hardly... There is at least 50% more mass in the 2x8 wall. How much more... I honestly don't know. But before I'd go slapping any old piece of glass in there, I'd be finding out how much mass that glass should really have. Make sense? Max

Sorry Quiet, I just got in from a festival I worked all day. Yes I meant that the glass is the same as drywall in weight. One of Knightfly's stickies shows the DENSITY of glass and drywall 2.5 and .8 lb/ft^2/inch). The one third for guideline actually slightly conservative. Glass is the density tempered or float. Laminate is slightly lightly due to the lighter plastic in between. I hope this helps somewhat from a sunburnt exhausted festival nut. Andre

... before I'd go slapping any old piece of glass in there, I'd be finding out how much mass that glass should really have. Make sense? Max

Yes ! Makes sense.

Yes I meant that the glass is the same as drywall in weight. One of Knightfly's stickies shows the DENSITY of glass and drywall 2.5 and .8 lb/ft^2/inch). The one third for guideline actually slightly conservative. Glass is the density tempered or float. Laminate is slightly lightly due to the lighter plastic in between. I hope this helps somewhat from a sunburnt exhausted festival nut. Andre

Yes! It helps ! If either if you guys want to weigh in with a follow-up, here's the deal. As soon as I get this rotten siding off my garage, my external wall is going up, and the single-pane window that will go in that wall. Its sister window will go in when I build the internal room. Pdf's are here. http://home.pacbell.net/needhame/clark.pdf The plans are accurate except that the external wall will be 1/2" plywood with 7/8 " stucco over that. Inside: Fiberglass insulation. The smallest airspace between that wall and the inside assembly will be 2 inches. Let's assume that we caulk obsessively & build our doors right, so we don't have a weak link anywhere else. My question is about the external wall only: Am I good to go with a 1/2" pane of glass in a wooden frame on neoprene setting blocks (i.e. a Rod Gervais-style window)? As per Andre's note, I am speaking of float or tempered glass, though Rod says in his book that tempered glass is superior to float glass for these applications. Alternatively - and at greater expense - the specs for glass bocks correctly installed seem to meet or exceed my needs as far as letting light in through thie external wall. Is this a legit alternative? I don't mean to beat an end-run around Max's advice to get an engineer on the phone & pay him some green to check the math. I'm just getting some mixed messages about how straightforward this is. If a 1/2 " pane of float glass will get the job done with this outer wall assembly, I can deal with what the inner wall needs another day.

By the way, that external wall is on 2 x 4 wooden studs.