Green Glue Between Two Layers of Drywall vs. Factory Damped Gypsum
Posted by BIP on 23rd May 2016
When a soundproof room design is executed, one question always arises by the contractor hired to do the build:
"Why should we use Green Glue Noiseproofing Compound and TWO layers of drywall when we can simply put up only ONE layer of Factory Damped Gypsum board?"
This sounds like a reasonable question because one layer would be half the work with similar results. The issue is not with the half the work argument, but rather the "similar results" part we need to explore further. This blog post is to analyze how these two construction methods add up when compared back to back.
PRODUCT INFO AND INSTALLATION What is Green Glue Noiseproofing Compound? Installation: Green Glue Noiseproofing Compound must be "sandwiched" between two rigid layers of building materials which in this post we will use two layers of drywall. Two 28oz tubes of Green Glue Compound are randomly applied to the back of the second layer of drywall. The second layer of drywall is then screwed onto the wall already with the first layer of drywall which squeezes the liquid based Green Glue compound into a very thin layer between the two sheets. The second layer of drywall should be installed so that no joints from the first layer of drywall lines up with the joints of the second layer (prevents air gaps). After about a month or so the water from the compound will evaporate and leave a thin layer of a sponge like "goo" which dampens the layers of drywall and absorbs vibration.
What are Factory Damped Gypsum Panels? Installation: QuietRock is installed the same way you would install any single layer of drywall without any mess from applying the damping compound. |
| Installation Summary: The contractor was asking to substitute Green Glue and two layers of drywall for one layer of QuietRock because its about half the amount of labor. One forgotten benefit of double layer drywall is the ability to stagger the drywall joints between layers which makes for a more airtight wall. Also keep in mind that the first layer of drywall does not need to be finished so the labor cost for the first layer of dyrwall should be less than the second finished layer. |
MATERIAL COSTS: Green Glue: Pricing for Green Glue Noiseproofing Compound from Buy Insulation Products (w/ Free Shipping) is currently the following: Using Pails ($252/pail = 365sf at 2 dispenses per 4x8 drywall) $22/sheet Cost of 5/8" Drywall (non-lite) $11.50/sheet
Total Cost = 2 x $11.50 = $23 + $22 = $45 per 4x8 QuietRock: At local lumber yards QuietRock 510 (1/2" thick) is $50 to $55 per 4x8 QuietRock: Hard to find but out there, the QuietRock 530 (5/8" thick) is $105 per 4x8 PRODUCT WASTE: When installing Green Glue and drywall there is bound to be a decent amount of drywall scrap that is thrown away after the project is over. When installing a factory damped panel the cost per square foot of scrap is much more expensive than that of regular drywall. The QR 510 is over $1.50/sf when normal 5/8" drywall is only 36 cents/sf. Also none of the Green Glue Noiseproofing Compound is scrap because what is applied to the second layer is used.
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| Material Cost Summary: The cheapest variation of factory damped gypsum on the market is the 510 (1/2") which is still $5 per 4x8 section more expensive than the Green Glue wall with two layers of drywall. The QuietRock 530 (5/8") can be found for a little over $100 per sheet. The clear winner in this category is Green Glue. |
STRUCTURE MEASURMENTS: ADDED MASS: Green Glue: 5/8" Drywall weighs approx 72lbs per 4 x 8 sheet. So using two layers will be approximately 144 lbs of mass per 4 x 8 section of wall.
QuietRock 510: (1/2" panel) weighs 68 lbs per 4 x 8 sheet THICKNESS: Green Glue: 2 layers of 5/8" drywall and a layer of Green Glue in between = 1-1/4"
QuietRock 510: 1/2" |
| Measurements Summary: If losing space is an issue, then going with Green Glue and two layers of drywall will subtract out 1-1/4 inches of room space or ceiling height. Factory damped drywall is thin and lowers that amount to 1/2"-5/8" depending on the panel you choose. In regards to added mass, Green Glue is the clear cut winner by adding a whopping144 lbs of mass compared to a measly 68 lbs for QR510 or 106 lbs for QR530. Mass plays a big part in lowering the resonance point of a structure, so the heavier the wall/ceiling the better it is for lower frequencies. These low frequencies are not fully represented in just an STC rating. |
ACOUSTIC TEST RESULTS: Standard 2 x 4 wood stud wall with each product on both sides.
GG: STC 55 (Test OL 05 1049) Standard metal stud wall with each product on both sides.
GG: STC 61 (Test OL 06 0942) | |
| Test Results Summary: The STC ratings for Green Glue Noiseproofing Compound and two layers of drywall are higher than factory damped panels. The Green Glue walls also have much more mass so resonance from low frequencies are also more controlled than the lighter factory damped panels. | |
OVERALL COMPARISON: GREEN GLUE NOISEPROOFING AND TWO LAYERS OF DRYWALL: PROS: Lower Material Costs Less Expensive Scrap Material Air-tight Seal (Staggered Joints) Control of Amount of Damping Compound Used Superior Acoustic Testing (STC Ratings) Much Larger Mass Addition to Structure (4.5 lbs /sf) FACTORY DAMPED GYPSUM BOARD: PROS: Lower Labor Costs (1 Layer compared to 2) Less Mess During Install Saves Room Space (1/2" or 5/8" compared to 1-1/4") As you can see, for superior soundproofing results you will be better off going with the Green Glue option, however Factory Damped Gypsum Board like QuietRock does offer a faster install with less mess. Both products have their places in the soundproofing market and its up to the end user to decide what fits their specific application.
ADDITIONAL BLOG POSTS RELATED TO THIS ONE: Keys To Wall Soundproofing: Lesson 1 Decoupling Green Glue Can Help You Easily Noiseproof Your Apartment Walls Should I Use Green Glue Tubes or Pails? What is Green Glue Noiseproofing Compound and How Does It Work? Size of Hat Channel For Use With Green Glue Noiseproofing Whisper Clips How to Properly Install Green Glue Noiseproofing Whisper Clips Best Soundproof Ceiling Options with Green Glue
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