So what's the deal with loose vs. tight insulation? - AVS Forum
Forum Jump: 
 
Thread Tools
post #1 of 7 Old 05-05-2013, 12:28 AM - Thread Starter
Senior Member
 
danielrg's Avatar
 
Join Date: Jul 2011
Location: Salt Lake City, UT
Posts: 217
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Liked: 16
I have been reading a number of build threads lately. Generally, people talk of "loosely" packing this or that soffit with insulation. Almost never does anyone just say they put insulation in it, they make sure to note that it was loosely packed.

So what's the big deal? Why make sure it's loose? Why not pack it in tight? Why care either way?

I did some searching around - and maybe I'm not the best searcher - but didn't find a thread where this specific topic was discussed - loose vs tight fill vs who cares.

Thanks!

Electrical engineer by education. Currently a system engineer. I like home automation, theaters, and blinking lights.
Someday it'll be more of an actual hobby - if my employer would ever let me go home!
"The Escape Pod" - My First Theater Build
danielrg is offline  
Sponsored Links
Advertisement
 
post #2 of 7 Old 05-05-2013, 04:18 AM
AVS Special Member
 
Johnsteph10's Avatar
 
Join Date: Aug 2004
Location: GA
Posts: 4,254
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 5 Post(s)
Liked: 18
It all has to do with air pockets in/around the insulation (for sound isolation, it is literally more on a molecular level). Packing the insulation simply removes that quality and increases the sound transference.

John

Loganed...finally. 6/6/08
My 3.0 HT Build Thread
Johnsteph10 is offline  
post #3 of 7 Old 05-05-2013, 04:37 AM
AVS Special Member
 
Pugnax555's Avatar
 
Join Date: Nov 2007
Posts: 1,817
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
Yep, basic physics. The tighter it's packed, the more solid the surface, the more it'll reflect sound. The looser it's packed, the more it will dampen/absorb sound.
Pugnax555 is offline  
post #4 of 7 Old 05-05-2013, 08:27 AM
AVS Special Member
 
jautor's Avatar
 
Join Date: Jun 2001
Location: Houston, TX
Posts: 7,606
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 46 Post(s)
Liked: 335
It's also a general installation comment about fiberglass insulation. Tightly packing (squishing, crushing) fiberglass batts ruins the insulation "R value". Since that's somewhat counter-intuitive, you almost always see the phrase "loosely packed" in this context - even outside of the theater / soundproofing conversations...

Rock Creek Theater -- CIH, Panamorph, Martin Logan, SVS PB2000, Carada Masquerade, Grafik Eye, Bar table, Green Glue, JVC RS50 
Theater build photos: http://photobucket.com/autor-ht

jautor is offline  
post #5 of 7 Old 05-05-2013, 08:51 AM
Member
 
brucebell's Avatar
 
Join Date: Mar 2013
Location: Near Atlanta
Posts: 15
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 10
The best insulator is a vacuum. The next best insulator is dead air space. Anything that can be done to prevent air molecules from bumping into each other improves both thermal and acoustic insulation. Fiberglass works by creating small air pockets in which the air molecules are relatively unable to move within and against/through the glass fibers. Compressing the fiber glass reduces the number and size of dead air spaces, allowing the glass to transmit thermal and acoustic energy.
brucebell is offline  
post #6 of 7 Old 05-05-2013, 01:39 PM
AVS Club Gold
 
warrenP's Avatar
 
Join Date: Jul 2005
Location: Now in Colorado!
Posts: 1,800
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Liked: 52
Yep, it is all about air movement. While some of the foam and solid insulation is excellent for dealing with temperature issues, those same insulation are usually ineffective for sound isolation. The key are the tiny little air pockets made between the fibers of the loose insulation. Each time the sound crosses an air pocket, hits the next fiber, and then goes through that fiber to the next air pocket, the sound levels decrease. When you "eliminate" those air pockets with dense/rigid/solid insulation you actually increase the amount of sound that is transmitted through the insulation.
warrenP is offline  
post #7 of 7 Old 05-05-2013, 10:35 PM - Thread Starter
Senior Member
 
danielrg's Avatar
 
Join Date: Jul 2011
Location: Salt Lake City, UT
Posts: 217
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Liked: 16
I knew I'd get great answers out of everyone. Many thanks! The only place where I have packed my insulation has been where I needed to fireblock. Of course I haven't really put any other insulation in than that yet. But this helps me to know how to fill my soffits. I have to admit - it's hard not to cram too much insulation into a space, you kind of have to hold back.

Funny Johnsteph10 - I've been reading your build thread on and off the last week - about 300 posts in. Going back in time to June '09 - almost 4 years ago now!

Electrical engineer by education. Currently a system engineer. I like home automation, theaters, and blinking lights.
Someday it'll be more of an actual hobby - if my employer would ever let me go home!
"The Escape Pod" - My First Theater Build
danielrg is offline  
Reply Dedicated Theater Design & Construction

User Tag List

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page


Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off