Replies

1. 
   BillHartmann | Mar 22, 2009 10:57pm | #1

   Try doing a search on my name and fiberglass and attic

   I had several different reports that I had found from Oakridge (DOE energy labs).

   They have chambers that can test whole assemblies and not just the individual materials that give the R values.

   The main problem that they found with FG was LOOSE FILL in attics where air could move across them. And the performance was much less than expected by the

   Many people extended those finding to applications of FG. But later studies show that is not true.

   However, FG does not reduce the amount of air leakage like cels can. And even without air movement FG does show a decrease in R value when tested at lower temps. Although there is a good chance that an attic would not get cold enough to make a significant difference.

   And the new chopped fiberglass, which is a soft cottony materail is much different. But I have not seen any studies that get into specific details.

   .
   William the Geezer, the sequel to Billy the Kid - Shoe
2. 
   USAnigel | Mar 23, 2009 12:30am | #2

   Think of it this way. Blown cells fills the space and drops in to every nook and cranny.

   A batt is way to straight and stiff and will span over areas leaving a gap. Some framing is straight and a good fit, but most is warped and the space to be insulated varies. 

   Cells is also much easier to "install" is most attics. Just push the hose out where you need it and shoot it in to depth.

   Fiber glass works as a filter as soon as the air starts to move. This is just what your trying to stop with insulation. Air will move through cells but you need much more pressure to do so.

1. 
   madmadscientist | Mar 24, 2009 02:12am | #4

   Ya I know that but the FIL is going to take some convincing....

   Daniel Neumansky

   Restoring our second Victorian home this time in Alamdea CA.  Check out the blog http://www.chezneumansky.blogspot.com/ 

   Oakland CA 

   Crazy Homeowner-Victorian Restorer

3. 
   Piffin | Mar 23, 2009 01:05am | #3

   You have only been married for a couple years so you have not yet learnt not to argue with your FIL, right?

   LOL

    

    

   Welcome to the
   Taunton University of Knowledge FHB Campus at Breaktime.
    where ...
   Excellence is its own reward!

1. 
   madmadscientist | Mar 24, 2009 02:13am | #5

   Not arguing with just don't want to see someone on a fixed income waste money...

   Something about putting lipstick on a pig?? Wastes your time and just annoys the pig?? How does that saying go?

    

   Daniel Neumansky

   Restoring our second Victorian home this time in Alamdea CA.  Check out the blog http://www.chezneumansky.blogspot.com/ 

   Oakland CA 

   Crazy Homeowner-Victorian Restorer

4. 
   Clewless1 | Mar 24, 2009 03:32pm | #6

   I'm used to seeing cellulose less expensive in an attic ... and logically more effective ... it is difficult at best to have fiberglass fill all gaps ... particularly in an attic ... assuming it is more 'truss like' than old fashioned ceiling joists only. But even then ... cellulose just gets better coverage ... it doesn't take no studies and rocket science to tell you that.

   Blown fiberglass I think has shown to be substantially less affective than cellulose because it lacks the density to resist air flow ... even though in a static conditioin (e.g. hot box test), it shows an R-value that is 'good'. Attics have MUCH more air flow than in an enclosed wall.

   Cellulose ... recycles paper and does a better job and usually for the same or lower cost. It doesn't take much to figure out what is best to use.  JUST DO IT.

5. 
   Danno | Mar 24, 2009 03:40pm | #7

   One of the most convincing arguments I heard was--"What is your furnace filter made out of?" Fiberglass. Air travels pretty handily through fiberglass. If you want to filter the cold air coming into your house through the walls or attic, it's great (or to filter the hot, moist air traveling the other direction).

1. 
   BillHartmann | Mar 24, 2009 04:07pm | #8

   That is one of the most unconvincing arguments that I have ever heard.Corvettes are also made out of fiberglass.Composition floor tiles, electrical wire insulation, and cheap blow up pool toys are all made from vinyl. But they all have very, very different characteristics..
   William the Geezer, the sequel to Billy the Kid - Shoe

1. 
   Danno | Mar 25, 2009 02:34am | #9

   Corvettes usually have some resin added to the fiberglass, but I get your meaning.

2. 
   EricPaulson | Mar 25, 2009 03:51am | #10

   If air movement is properly restricted fiberglass is a decent insulation. It's all in the details. 

1. 
   Danno | Mar 25, 2009 02:29pm | #11

   I agree--but lots of people install f.g. expecting that it, by itself, will stop air flow--and it won't (well, kraft faced if stapled well is okay--but does not seem to stop convection currents in the stud bay, for instance).

1. 
   EricPaulson | Mar 25, 2009 02:46pm | #12

   agreed 

6. 
   GaryGary | Mar 29, 2009 02:05am | #13

   Hi,

   Here are a couple:
   http://www.homeenergy.org/archive/hem.dis.anl.gov/eehem/92/920510.html

   http://www.foam-tech.com/theory/rvaluedrift.htm

   Gary