Replies

1. 
   Clewless1 | Feb 07, 2009 08:35am | #1

   Blowing a pitched roof/ceiling can end up with insulation that settles into the eave. You need baffles at the intersection of the eave/wall to prevent this w/ blown. This will depend a lttle in part on the slope that you are talking about; you might get away with it at a lower slope. Open eaves, though will never really allow you to insulate properly, I think. What is the distance of the sloped area ... wall to flat attic?

1. 
   Tuna1 | Feb 07, 2009 06:14pm | #3

   thanx for you help.. I do in fact have baffles.. here in Tucson the roofs are framed with 24 OC rafters (we don't get snow), the ridge is about 5 feet, attic ceiling to top and the run out is about 18 feet, rafters are separated at outer wall edge by baffles with 3 or 4 inch bored out holes, screened to keep critters out. Baffles are just under 24 inch wide and maybe 8 inches tall. You think blown in will be a problem with my set up?? The appeal, I understand, is that blown in makes a much better seal around everything that passes through the ceiling into the attic (vents, etc.) than simply laying out rolled insulation. Thanks again

1. 
   Clewless1 | Feb 07, 2009 09:51pm | #4

   I don't hear you describing baffles ... only blocking between the rafters w/ vent holes in them. A baffle is like a cardboard item that will prevent the blocking of those vent holes with insulation blown in. They also maintain that 1 inch air space above the insulation for like the first couple of feet in from the exterior wall.

   Conceivably you could go in your attic and shove the blow hose down the rafter bay and blow it ... but then you plug/block your vent hole and fill the entire cavity up to the roof deck ... entirely eliminating the attic venting that is important.

   If you could fabricate a baffle that slides down the rafter bay and sits at the bottom that will 1) maintain clearance for the vent hole and 2) provide a 1 inch air space above for the 1-2 ft perimeter above the exterior wall, .... you would be in good shape.

   This is a typical situation found frequently in existing/older construction. Maybe they make such a beast that you can simply slide into place and then shove down the bay. Maybe an insulator can answer that question. Other option would be to design such a thing and fabricate them out of cardboard or other material. When you shove the hose down there, you would have to make sure it is under the 1 inch vent space else you blow where you don't want.

   Someone else must have some solid experience with this kind of thing to take the edge off my grey areas, here.

2. 
   Clewless1 | Feb 07, 2009 10:07pm | #5

   This video shows the baffles ... behind the blocking (he calls it 'bird board'). Not a very good explanation ... but you get the idea.

   http://www.expertvillage.com/video/59990_inspecting-insulation-baffles.htm

   also try this ... gives you a few more hints.

   http://www.energy.wsu.edu/documents/code/bfg/2006/Chapter_04-2006A.pdf

   I was looking for a good general baffle detail, but couldn't find one easily. You have 18 ft attic edge to the outside wall running along the rafter? No knee walls? Got a pic?

1. 
   Tuna1 | Feb 08, 2009 12:35am | #6

   thanx again for your help... yes, total span is 36 ft bout... ridge line to outside wall is about 18... framing is a system of trusses with rafters 24 inch on cntr., rolled insulation laid out in bays... rafters sit on beam/top plates at outside wall with baffles(with bird holes) between... obviously this limits my ability to crawl outward with rolled insulation of a higher r value to lay on top of existing insulation... was suggested to blow it in... am wondering if this is the way to go.. thanx again. Tuna

2. 
   Tuna1 | Feb 08, 2009 12:54am | #7

   hold the phone... I got up into attic crawl space and sighted out to roof/wall junction... just like in the video you referred me to I do not, repeat, do not have an underside of plywood paneling fastened to roof sheathing that serves to permit air flow through bird hole, so I would risk blocking that flow entirely if I put in blown insulation.. looks like I'll have to roll it out,,, but that's ok... need air flow big time in hot AZ... when the house was built they rolled it out almost to the roof/wall... as the roof pitches downward there's less and less room to roll in insulation but they did leave space for air passage through the bird holes.. thanx again, tuna

2. 
   allaroundcobber | Feb 07, 2009 05:55pm | #2

   If your house is 1oo years old or so the rafters probably sit on the outside beam with no air space. chances of filling soffit are unlikely.

   Moe