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-   -   Rigid foam for window plug (http://www.avsforum.com/forum/19-dedicated-theater-design-construction/1616426-rigid-foam-window-plug.html)

LeChuck 07-24-2014 07:07 PM

Rigid foam for window plug
Hi folks,

I am currently setting up my home theater room. It's in a half sunk basement, which procures some decent insulation (to the outside) but has a large window (72*35). The window has dual pane glass but it is still the weak point. I'm building a frame for it and will install some removable window plugs. They'll be about 3 inches thick, including the 2 wood faces.

I'm wondering what would be the best insulation material to use between those faces in order to get the best soundproofing for the window.

I've used rigid foam insulation from R-Tech on my garage door (that was for heat protection), it's available at the local HD, in 1.5 inch thick boards. I also have a roll of R13 pink insulation, which could fit, compressed to 1.5 inches or 2 inch, depending on the thickness of the wood.

So, rigid foam vs pink R13, would it make any difference?


LeChuck 07-25-2014 07:35 AM

Another quick question: what about the plug being made *only* with something like a 2 inch thickness of rigid foam (plus a board of wood at the front)? Would that be efficient for the purpose of insulating the window (for minimal sound to be heard from outside)? 3 inches is possible as well. This would be simply quicker and easier to build and fit tight. The foam would be glued to boards as a front face, which would then be covered in fabric, with a lip to fit around the window opening (which was not created straight at all). This would also make it a lot lighter to put up and down when needed. Perhaps velcro would be the only thing needed to keep it secure. There would be an air gap between the back of the foam and the window.

BIGmouthinDC 07-25-2014 09:09 AM

damped mass usually trumps insulation when it comes to blocking sound. I would use a couple layers of 1/2 inch MDF with Green Glue between layers and at least an inch of a sound insulation product like OC703 or OC705. IMHO rigid foam doesn't offer much in the way of sound attenuation.

LeChuck 07-25-2014 09:12 AM

Thanks. Understood about the MDF. The sound insulation products are not available locally and all I can get is pink insulation or rigid foam, nothing else...It doesn't look like Green Glue is available locally either...

BIGmouthinDC 07-25-2014 09:21 AM

define locally

LeChuck 07-25-2014 09:25 AM

At any Home Depot or Lowes, or hardware stores in town...

I don't want to order any of this stuff online, especially since I do not need it in any large quantity. MDF, pink insulation, rigid foam, all of this is readily available, so I'm trying to see how best to insulate the window (or in other words more insulation than just the glass) with readily available materials. Local stores don't even carry rockwool or denim insulation.

LeChuck 07-25-2014 10:28 AM

After researching a bit more and reading another thread, I'm going to try a simple plug with 2 layers of 3/4 MDF glued together with wood glue, and felt around the perimeter for a tight fit and see how that works out first...

That might be a bit heavy but still manageable for the occasional opening.

BIGmouthinDC 07-25-2014 11:26 AM

you can buy individual tubes of Green Glue on line and local commercial building suppliers will have insulation alternatives.

LeChuck 07-25-2014 12:08 PM

Is the Titebond acoustical sealant similar to Green Glue?

BIGmouthinDC 07-25-2014 02:40 PM

no, there are several brands on acoustical sealant on the market that all function about the same basically heavy bodied stays flexible caulk that you use to fill gaps.

Then there is material used for viscoelastic dampening between two sheets of material. Green Glue is one of those products.

Cthanatos 07-25-2014 07:40 PM


Originally Posted by LeChuck (Post 26038834)
Is the Titebond acoustical sealant similar to Green Glue?

The answer to that would be a no. Green glue is used as a damping agent, something you spread between the layers you're using (like the meat on a sandwich), like between two layers of drywall. The acoustical sealant isn't a damping agent, it's used to seal the cracks and spaces where two places meet, as stated on the website "The sealant is used for unexposed applications at perimeter joints, floor and ceiling runners "

sheesh, I started this response 5 and half hours ago, at work and forgot to submit... XD

LeChuck 07-26-2014 08:16 AM

Makes sense, thanks :)

TMcG 07-26-2014 05:05 PM

If I may....why would you worry about sound escaping into the open world through a basement window? I understand using a plug for light control while still being removable, but I guess I don't understand what the big deal would be if some low frequency sound passed through a foam plug and made it to the outside.

If you are not planning on removing this plug very often (or at all), then I would be a bit concerned about the potential for mold growth. Mold needs air, water and a food source to grow. Assuming the window has a vinyl casing, making a foam plug and sealing with an antimicrobial caulking will completely eliminate any food source and severely limit the amount of air and water - both of which would be dependent on the quality of your window more than anything else. With MDF or any wood-based product, you've now provided a food source. Yes, you can seal it, prime it, paint it, etc., but the felt boundary on the edges would not be as air tight.

LeChuck 07-26-2014 06:40 PM

I'm just trying to limit the amount of sound reaching the neighbor's house. Peace of mind for when I'm watching Saving Private Ryan :) I honestly can't tell how much extra insulation will do the trick and perhaps it won't take much.

I won't touch it every day but I expect that I will open up regularly to let light in and air it out, especially if I know that I won't be in there every day.

I am not too concerned about mold and water, though, out here in Tucson, AZ.

The good thing is that as long as I can block out the light, for a start, and put up *some* insulation, it's not set in stone and there is more time to experiment with the window plug itself. I've been working on a casing for it because neither the window nor its framing were built straight. I'll shim that and seal the gaps then work on the actual plugs.

TMcG 07-27-2014 03:13 AM

A car driving by on the street will provide far more noise energy into your neighbor's house than your theater system ever would...even during "Saving Private Ryan".

A few years ago I had my Revel Ultimas set up, along with FOUR Revel B15 subwoofers. Our exterior walls are (unfortunately) standard 2x4 construction with pink fluffy insulation, OSB exterior cladding and Hardiplank and has 8 large double-pane windows. I played some heavy Metallica with the volume turned up way beyond reference and went outside. I could hear it quite clearly, but as I walked toward my neighbor's driveway 20 feet away, what was clear to hear turned into a low rumble. By the time I reached his open garage, I could only hear the faintest rumble. When the garage door (uninsulated aluminum, fyi) was closed....nothing....absolutely nothing could be heard.

If this same system dropped straight down into my walk-out basement, the effect would be greatly diminished, especially with a single high-mounted and much smaller window.

LeChuck 07-27-2014 06:27 AM

You may be right. Although when the neighbors are outside talking out loud, I can hear them through the window and this is what I'm basing this on. It's possible that what I'll put up for light blocking will be enough added insulation or that foam will do the trick.

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