adding insulation

me again.
it gets cold here in philadelphia, and hot in summer.
i want more insulation.
my joists are 5 1/2" deep. my rafters are also 5 1/2" wide. if i put more loose fill between the joists, to the max of 5 1/2", and the max on the roof, which would be 3 1/2" batts (5 1/2 minus 2" for air space between roof and batt), will this increase my R value to whatever 9" equals?
alternatively, are there any secrets for applying 12" insulation to rafters only 5 1/2" deep?
hope my terms are understandable.
as always, thank you.

 

I think Im lost here. If this is all one attic why would you put insulation up there in the roof rafters??????????. For an attic you want to put the foam forms in the rafters by the plate so the air from the over hang vents can get into the attic and out. Then go for the 12" for sure all over the ceiling joist. Thats it ,make sure you have roof vent up there and open also. We like to think of the roof as something that keep the rain ,snow and sun off the insulation thats there for the home and thats all ED

 

sorry ed
i don't think i know the difference between a rafter and a joist.
but anyway, when i stand in the attic there is no insulation above my head, and about 3 1/2" of loose fill under the plywood under my feet. the space under my feet is only 5 1/2"deep, so unless i raise the plywood up another 7" i am limited by how much more loose fill i can blow under there.
when i look up at the naked inner surface of the roof, i can't see how a 12" thick batt would be attached. those beams or joists or rafters or whatever there called are, say 2"x5 1/2"x12 feet. so what do i attach the batt to? ( as 12" is fatter than 5 1/2").
thanks again

 

For get the roof rafters over your head . Dont think are look at the roof there over your head . It should just be wood there and that is all no no no insulation. Some holes for button vents up out side on the roof for vents. The only place you can put insulation is under what you are standing on and thats the only place.If you take the plywood up dig out the old you can put a paper side down
R 19 and that is it . Then put the plywood back. you cant put more insulation in there and compress it . If you do you will lose the R value of it. ED

 

thanks ED.
but now i'm so depressed that i can't have R38-R49 under my cold attic feet...

 

Hi wrightideas

I agree with Ed. By putting insulation on the roof sheathing between your rafters may look like the easy thing to do. But you will not only block off your ventilation (I hope you can see holes where the vents are from the attic) you will bake your shingles in the summer. You should have more than R-19 in your attic, So for that to be achieved you would have to remove the plywood and install more insulation to get to the desired R-38 to R-49.

 

okay. the ply wood goes.
this is such a neat website!
thanks