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[eggdog23]

I want to try a window plug before putting in a window with 1/2 inch laminated glass.  Any idea on the thickness of soundproof foam that would equate to that type of glass?

Thanks!

Aaron

[johnbergstromslc]

If you have a double glazed unit, then add 1/2 thick glass with an airspace, your STC rating could be as high as 50.  There isn't a reasonable thickness of foam that can get you that - we're talking feet, not inches here...

The foam isn't what blocks the sound, it's the mass of the window plug.  The more, the better.

[eggdog23]

Thanks.  That is helpful--I wanted to make sure that if a window plug solved our noise problem that we would not end up being disappointed by a window insert that did not perform as well.

Great site by the way.  I have been searching for a few weeks and there is not a lot of information out there about residential noise abatement.

We have Pella windows, which according to their website have STC ratings of 27 for the venting and 28 for the fixed.  Pella also makes a laminated glass window with an STC of 34.  To equate that to a window plug, would you figure the different weight between the glass and then get the same weight for foam?  I did not think that difference was great enough to put money into changing out the glass, but I would be curious in seeing the difference that would make.

[johnbergstromslc]

Honestly, ditch the foam.  If you're going to replace the window and think the laminated glass is a good investment for the price, do that first.  A 34 STC is still not too shabby.  If you need more noise reduction, I suggest you make a plug, not out of foam, but plexiglass.  A 4' X 8' sheet of 1/2" thick runs about $250.  If you have some good sealing and a couple inches of airspace, you can expect an STC in the mid-40's, maybe more. 

By using plexiglass, you'll retain the view, too...

[bjnash]

I want to try a window plug before putting in a window with 1/2 inch laminated glass.  Any idea on the thickness of soundproof foam that would equate to that type of glass?

Thanks!

Aaron

The window plug needs to be as thick as possible and yet not take up all the space in the window frame, leaving an air gap between it and the window glass.  This dead air space really works for you as sound does not pass through it very well.  It's the dead air space and the sound blocking/absorbsion qualities of the foam that together are responsible for the sound reduction.

If the existing window has any sound blocking qualities at all and is sound without air leaks, noise reductions of over 50% can usually be attained.

See
http://www.soundproofing.org/infopages/windowplug.htm

We have found that if you wish to use plexiglass as a secondary window instead of a plug, the law of diminishing returns starts at 3/8".  That is anything thicker than 3/8" is a waste of money as the results are so small that it's not worth the extra cost.

Around here in San Diego, plastics places quote $12 a sqare foot for it and if you want non-yellowing it's more....
2" thick closed cell foam is about $8 a sq. ft. here at the Super SOundproofing Co.

Contrary to popular belief, the glass of a window is only part of the story.  The frame and framing are equally important.

BJ Nash

Super Soundproofing co.

[eggdog23]

Is there a difference between plexiglass and polycarbonate (Lexan), in terms of which is better for a sound window.

[bjnash]

I assume you are querying regarding our article on secondary windows at
http://www.soundproofing.org/sales/magnetseal_windows.htm

Do not use Lexan as it is almost unbreakable.  This would be a saftey factor to escape out a window.  Otherwise, ordinary "Lucite", "Plexiglass", etc works just fine.  If you are concerned with yellowing over time, you can buy "Museum" quality clear plastic that will not do so.

Do not use real glass because of the breakage factor or "Home Depot" plastic as it's too thin to be effective.

BJ Nash - Senior Soundproofing Technical Specialist
Super Soundproofing Co
www.soundproofing.org
888-942-7723