Replies

1. 
   USAnigel | Mar 02, 2008 10:04pm | #1

   Fiber glass is the cheapest to buy and install but this also means its the weakest performer. My present house is "high speed builders cheapest guy" install and when the outdoor temp drops below 35f the feeling of warmth changes in the house to one of cool.

   Tight packed cellulose is a little more cost but has much lower convection currents than fiber glass. I just had this installed in a project and it gets in everywhere, behind all the electric boxes which does not happen with fiber glass.

   Sprayed foam is by far the best as it seals all the gaps and cracks from building. But the install price is the highest.

   What's picked comes down to who is paying for the install! Unless the buyer has some input they will get the cheapest stuff!

2. 
   Piffin | Mar 02, 2008 10:47pm | #2

   Denspak cells or Bibbs have almost no convection heat loss

    

    

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

1. 
   mmoogie | Mar 02, 2008 11:30pm | #3

   Piffin,Have you done much of the DP cells yourself? I love the end result, but cannot seem to get it done very quickly. Using insulmesh and a force2 blower, I can't seem to get more than about 40 bags a day into the structure. I just put 100 bags into a 14x20 room, and it took a day to get the web up, and three days to blow. I'm always thinking there's got to be a way to get it done a little faster.Steve

1. 
   Piffin | Mar 03, 2008 06:26am | #4

   I hire it done. I hate to be around the stuff.

   Mike Smith and others here do it themselves. 

    

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

1. 
   mmoogie | Mar 03, 2008 07:32am | #5

   How much does your sub charge (roughly, of course). Does he charge by the cubic foot? If foam is still about 1.20 cf (as it was around here last I checked) What do you think cells should cost in relation to that subbed out?Sorry for the hijack, BTW, I'll go away now.Steve

1. 
   Piffin | Mar 03, 2008 07:34am | #6

   a third of that 

    

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

2. 
   mmoogie | Mar 03, 2008 07:54am | #7

   Thanks.

3. 
   Riversong | Mar 03, 2008 10:28pm | #8

   Convective heat loss in blown insulation is a problem only with fiberglass.  Cellulose is so resistant to air movement that it is allowed in some areas as a firestop.

   Cellulose also has much better sound attenuation qualities, is insect-proof and resistant to rodents, and highly fire-resistant.

   It's not that it's "best" to blow open attics at lower density, it's that it's the only way to blow attics, as you're relying on gravity to settle the material.  Cellulose in an open attic will settle to approximately 1.4 lbs/cf, whereas dense-packed in a wall cavity should achieve 3.1 lbs/cf.

    

   Riversong HouseWright

   Design *  * Build *  * Renovate *  * Consult
   Solar & Super-Insulated Healthy Homes
4. 
   DanH | Mar 04, 2008 12:34am | #9

   Riversong gave a pretty good summary. Convection losses are related to how easily you can blow air through the material, and fiberglass is generally the worst in this regard. If the fiberglass is densely packed it helps, but that kind of density is really only achieved with high-density batts, and even the best are likely worse than cellulose.

   Re ceilings, convection isn't as much an issue for cooling as it is for heating, since with cooling the cold air will tend to fall and stay in the insulation.

   If your view never changes you're following the wrong leader
1. 
   cutdude | Mar 04, 2008 04:06am | #10

   Thanks to all who responded to my question. Sure sounds like cellulose is the way to go.  I did hear from an fiberglass installer that the fire-proofing treatment is lost over time, is there any truth to this or does he claim this because he doesn't work with it?

   Thanks again. Jim

1. 
   Riversong | Mar 04, 2008 06:50am | #11

   No truth to it. 

   Riversong HouseWright

   Design *  * Build *  * Renovate *  * ConsultSolar & Super-Insulated Healthy Homes

2. 
   DanH | Mar 04, 2008 02:29pm | #12

   Only if the stuff is repeatedly wet.
   If your view never changes you're following the wrong leader

5. 
   cargin | Mar 04, 2008 04:59pm | #13

   cutdude

   Just a thought.

   You could cover the whole ceiling with 2" EPS. Then fur out the ceiling with 2x4s.

   Run all your wiring along the the furring strips. Keep pentrations of the EPS to a minumum, like bathroom fans and plumbing vents.

   Then blow all the cellulose you want on top.

   I have been in too many attics with poor top plate to rafter detailing. I have see 6' to 8' of the attic sweep clear of insulation by strong winds.

   I was called in because of the extreme amount of mold growing in the corner and on the ceiling. 

   Piffin says he has done it and has posted pics but I have not found them. I have only done it on remodels.

   It would add about $1 SF material cost.

   Rich