Comparing Green Glue (GG) and Resilient Bar (RB)

This page is based on fully independent, 3rd party test data comparing Green Glue (a visco-elastic sound damping material) and Resilient Bars. Resilient bar is a well established and common sound isolation product and costs less than Green Glue. So Green Glue needs to demonstrate a considerable level of superiority in order to be a viable alternative. The Green Glue and resilient bar tests were performed in the same test lab so the data here is as reliable as it gets.

Is Green Glue Superior?

Once you’ve read to the bottom of this page you will have seen that Green Glue not only outperforms resilient channel is raw sound proofing performance, but also brings a number of other advantages to the table. For example, it is easy to ‘short circuit’ a resilient bar installation by accidentally bridging the plasterboard and stud-work. However if you use Green Glue and Resilient channel in combination you will not suffer a loss of sound proofing performance ever if it has been short circuited. The effects of a short-circuited Green Glue and resilient bar wall were tested. Even though the 64 square foot specimen contained no less tan 16 short circuited locations, the STC (Sound Transmission Coefficient) was a full 3 points higher than a correctly installed resilient bar wall without Green Glue!

The test were performed at Orfield Laboratories, an independent NVLAP accredited lab in Minneapolis, USA, during May and August 2005.

Part 1 – Test Description

The following test was employed to evaluate the performance of Green Glue in combination with resilient bar.

Wall construction details, from the source room to the receive room:

Resilient Bar Assembly	Resilient Bar Assembly with Green Glue
Double 12.5mm plasterboard	Double 12.5mm plasterboard with 2 tubes of Green Glue per 8’ x 4’ sheet (sandwiched between the layers)
25 gauge resilient bar, perpendicular to the studs and 600mm on centre	25 gauge resilient channel, perpendicular to the studs and 24″ on centre
2×4 single wood studs, 600mm on centre	2×4 single wood studs, 600mm on centre
R13 Fiberglass insulation	R13 Fiberglass insulation
Double 12.5mm plasterboard	Double 12.5mm plasterboard with 2 tubes of Green Glue per 8’ x 4’ sheet (sandwiched between the layers)
OL 05 1011 – proper installation	OL 05 0825 – Proper installation OL 05 0828 – 4 short circuits OL 05 0826 – 1 short circuit OL 05 0829 – 8 short circuits OL 05 0827 – 2 short circuit OL 05 0830 – 16 short circuits

Green Glue and Resilient Bar in Combination

A minimum sound proofing performance figure is a legal requirement in many cases such as when converting a single building into dwellings. Failed Part E sound tests can lead to very costly rebuilds and / or legal action. An STC of 50 or more is a minimum requirement in many locations and it is possible, with increasing attention being given to the negative effects of noise, that the regulations will become even more stringent with time.

Based on the following assumptions, Resilient Bar provides the most practical and cost effective way of achieving a high STC value:

(1) Flanking noise (noise travelling along air ducts, through doors, over the top of walls through a ceiling cavity – any noise which passes not through the wall itself, but via an alternative path) is not an issue.

(2) The resilient bars are installed correctly (without ‘short circuits’ – where the plasterboard screws go through the  plasterboard and resilient bar into a stud behind with considerable negative effects on the performance).

(3) The resilient bar is of an effective design and construction.

It is no lie that resilient bar systems can produce impressive STC’s. But in a real world scenario, incorrect installation through short circuits is worryingly common which in many cases completely negates the benefits of having the resilient bars at all.

Resilient Bar Walls can be short circuited in other ways once the construction is finished, especially if people are not aware of the internal wall construction. For example, shelves and flat screen televisions may be fitted at a later date and the weight can cause the resilient bars to sag and press against the stud-work.

The potential for short circuits to occur is high but by eliminating the effects of short circuiting, resilient bar provides a far more consistent approach to sound proofing.

The 16 short circuit positions are numbered in the photo above. At 8 short circuits per 8′ x 4′ plasterboard, the extent of the problem far greater than it is likely to be in a real world scenario.

Chart 2 – Resilient Bar Short Circuit Test Results

As you can see, Green Glue demonstrates a remarkable ability to deal with resilient bar short circuits.

This table contains the RW and OITC averages for the tests performed.

Even when using timber furring strips, arguably equivalent to a completely short circuited resilient bar assembly Green Glue results in a higher STC result than a correctly installed resilient bar system. Bear in mind that STCs of 54 and higher may even be limited by flanking noise effects present in the lab. If you can’t find the test report you are looking for contact us. Green Glue could be just the product you need to prevent failure of your resilient bar walls or ceiling.

Green Glue (GG) as an alternative to Resilent Bar   (RB)

Let’s now look at the advantages of pure Green Glue systems in comparison to resilient bar systems where wide frequency band performance is a priority. In music rooms, home cinemas and rooms where traffic noise is a problem, low frequencies pose a considerable challenge. The STC system only accounts for frequencies about 125Hz and the OITC system only applies above 80Hz. Low frequencies are inherent to most sound proofing problems and by far represent the biggest challenge in any sound proofing project. Since STC overlooks low frequencies it is not a useful measure of performance in the majority cases.

Part 1 – Description of Test

In order to compare Green Glue and resilient bar, we once again tested equivalent walls in the same lab. We used the same acoustic insulation, stud spacing and gauge etc. The only differences were that one system used resilient bar and the other used Green Glue.

Wall configurations, from source room to receive room:

Resilient Bar Assembly	Green Glue Assembly II
Double 12.5mm plasterboard on 25 gauge resilient bar, perpendicular to the studs and 600mm on centre	Double 12.5mm plasterboard with 2 tubes of Green Glue per 8’ x 4’ sheet (sandwiched between the layers)
2×4 single wood studs, 600mm on centre	2×4 single wood studs, 600mm on centre
R13 fiberglass insulation	R13 fiberglass insulation
Double 12.5mm plasterboard	Double 12.5mm plasterboard with 2 tubes of Green Glue per 8’ x 4’ sheet (sandwiched between the layers)
OL 05 1011 – proper installation	OL 05 1035

Green Glue in combination with resilient bars

As previously stated, a minimum sound proofing performance figure is a legal requirement in many cases such as when converting a single building into dwellings. Failed Part E sound tests can lead to very costly rebuilds and / or legal action. An STC of 50 or more is a minimum requirement in many locations and it is possible, with increasing attention being given to the negative effects of noise, that the regulations will become even more stringent with time.

Chart 3 – Resilent Bar VS Green Glue

A comparison of Green Glue and resilient bar with 3 total layers of 12.5mm plasterboard.

The lab verified the resilient bar to be 25 gauge (as is most common), and that it had been installed correctly.

Note: whilst the resilient bar produces an excellent STC, the low frequency performance is vastly inferior to the Green Glue system. If the resilient bar had not been correctly installed, as is common, the difference would be even greater.

Summary of Performance	Reference I single 12.5mm sheet on both sides	Resilient Bar Assembly	GG Assembly I 1 Layer on Source Side	GG Assembly II 2 Layers on Both Sides
Rw	40	55	52	56
OITC	29	37	36	40
Flat Noise Reduction, dBA*	38	49	48	50.4
Test Number	OL 05-1003	OL 05 1011	OL 05 0416	OL 05 1035

* Whilst flat noise reduction, dBA is not an official standard, we regard it to be superior to STC and OITC for music and home cinema applications where a lot of low frequency control is required. The calculation is based on the ISO 226 Equal Loudness standard and draws on a frequency range of 31.5Hz – 5KHz.

* An assessment of wall performance that is not an of?cial standard, but is utilized by Green Glue Company as a superior method to STC or OITC for music and theater applications where low-frequency content is high. It calculates using the ISO 226 equal loudness standard, and using a bandwidth of 31.5-5000Hz.