Replies

1. 
   Piffin | Feb 12, 2004 03:17am | #1

   Sounds good if you be suyre to seall all joints in the foam board tight with spray and tape so no moisture can pass upward. You probably will eliminate dewpoint but you don't want a space full of damp cellulose either. That will supporet mold and will lose insulation value.

   Mike Smith might differ with me.

   BTW, I am out on Islesboro. Howdy neighbor

   bob pricce might have some advice for you too. He's the guy around here. RH Price Insulation Co

    

    

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   Taunton University of Knowledge FHB Campus at Breaktime.
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1. 
   xMikeSmith | Feb 12, 2004 04:48am | #2

   piffen ... that was my only concern... is the polyiso on the wrong side of the dew point....

    the denspak should be a good air retarder.. but any chimneys will put the warm moist house air in contact with the polyiso sheet... let's say it's a nice warm january night in Maine.... what ... - 15 deg F ?

   ok.. what's teh temp on the warm side of the polyiso?

   hmmmmm.... and it will make a pretty good condensing surface... it will be ok if the denspak has no voids... but any holes may become problem points...

   i like the polyiso, but i'd rather have it on the warm side of the roof rafters  with the denspak behind  and the baffles still in place... or not...

   ie:  air baffles or solid pak..... either way.. but keep the vapor retarder ( the polyiso ) on the warm sideMike Smith   Rhode Island : Design / Build / Repair / Restore

1. 
   Piffin | Feb 12, 2004 06:00am | #4

   Mike,

   He's not talking polyiso, but the blueboard, which I take to be extruded foam. I miss read the detail about placing it between the rafters though. I was seeing it across the bottom of the rafters with strapping holding it up and then blowing the cells above that. With it sealed to VB tight, that would be a good job if no penetrations leaking, right? 

    

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

2. 
   simonc | Feb 12, 2004 05:38am | #3

   piffin,

   i forgot to mention that i will be sealing the blueboard with spray foam and putting a vapor barrier so that should stop any moisture problems.

   simon.

1. 
   Piffin | Feb 12, 2004 06:08am | #5

   Read it all again then. You are on the right track but see the suggested improvement 

    

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

1. 
   simonc | Feb 12, 2004 04:04pm | #6

   Piffin,

   What suggested improvements are you talking about?

1. 
   xMikeSmith | Feb 12, 2004 04:34pm | #7

   i think he's saying the same thing i am... nail the blueboard to the bottom of the rafters .. no thermal break .. densest layer on the warm side..

    or he may mean something else... he is a MainerMike Smith   Rhode Island : Design / Build / Repair / Restore

2. 
   simonc | Feb 12, 2004 04:45pm | #8

   Mike,

   I plan to nail the blueboard to the underside then strap over it then blow in the cellulose into the rafter bay cavity through holes in the blueboard. Does this make sence?

   Edited 2/12/2004 12:12:38 PM ET by simonc

3. 
   xMikeSmith | Feb 12, 2004 08:15pm | #9

   ubetcha...Mike Smith   Rhode Island : Design / Build / Repair / Restore

4. 
   Piffin | Feb 13, 2004 12:52am | #10

   You got it right. The way it was first worded, it could be read that you were going to put the insaulation board between the rafters instead of across them. 

    

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

5. 
   simonc | Feb 13, 2004 08:23pm | #11

   Thankyou guys for the advise...... Simon

6. 
   rasconc | Feb 13, 2004 08:32pm | #12

   Sort of a hijack but an alternative I have not seen mentioned.  Has anyone use the recycled blue jean insulation?  I helped on a store that had the batts, they were heavy and a bit dusty.