# Shake & Rake or Blown in???



## PoleCat (Sep 2, 2009)

I have a 144sqft addition that used to have a flat roof over it. A 5:12 pitch roof has been built over this area now but the original cavities between the joists are empty. The old decking is still in place so I need to get insulation in there the hard way. Can the blown in fiberglass bales be used like the shake and rake material? i.e. I don't want to rent the blower for just 60 cu. ft. of material.:huh:


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## oh'mike (Sep 18, 2009)

I've used the blown in cellulose and the machine rental was free----

I've never used the fiberglass---however in that awkward space--the blower would sure be the ticket-----That machine easily tosses the product 12 to 15 feet---


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## PoleCat (Sep 2, 2009)

The machine appears to be a two man act. I am flying solo. My thoughts were along the lines of cramming it through the cavity with a ram rod like they used to do wadding in the old cannons.


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## oh'mike (Sep 18, 2009)

You are right--you need a feed and a spreader---so the shake and rake method sounds like the best option----yucky job------


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## Gary in WA (Mar 11, 2009)

You probably will have condensation problems because of the old roofing (if still present) acting as a vapor barrier, limiting drying to only the interior....http://www.buildingscience.com/docu...archterm=attic+fiberglass+batts+in+flat+attic

Further; http://www.greenbuildingadvisor.com...joe-lstiburek-says-dont-dense-pack-unvented-c

Wet fiberglass lose 60-70% of R-value; http://archive.nrc-cnrc.gc.ca/eng/ibp/irc/bsi/90-controlling-heat.html

If asphalt sheet roofing, figure a Class 1 vapor barrier on the wrong side of roof cavity for your climate; http://www.buildingscience.com/documents/reports/rr-0410-vapor-barriers-and-wall-design

Need to insulate your "closed" roof system correctly; with foamboard under/over the decking then fiber below to move the dew-point to prevent condensation per location/climate zone- chart; http://www.buildingscience.com/docu.../irc-faq-conditioned-attics?searchterm=attic+

Basics; http://www.buildingscience.com/documents/digests/bsd-102-understanding-attic-ventilation?full_view=1

Gary


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## PoleCat (Sep 2, 2009)

The old roofing has been removed. The 1X8 decking is still there but has 1/4 to 1/2" gaps between boards and various other openings here and there. Of course the outside edges had to be cut back to accommodate the new rafters. It should vent OK. I found me a hillbilly insulation blower in the back yard yesterday - our old Eureka upright vacuum. I'll post a video if it works.


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