Blowing in more attic insulation?

I want to add a layer of cellulose insulation over the 8″ of fiberglass bats over 6″ of vermiculite in the attic of a 1960 rambler in Minnesota, there are foam vents between some of the rafters for soft ventilation and i was wondering how much I could put in without restricting the soft ventilation and if i filled it up to the roof boards if the insulation would settle enough to allow some air to get to the softs. How deep would you go with the cellulose?
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>>How deep would you go with the cellulose?
Density is an important measure,as well.
How much depends on your location/climate.
I don't know about yours, but my church isn't a hotel for the holy, it's a hospital for sinners
Sojourners: Christians for Justice and Peace
Put as much R value in as you want, (the more the better )without blocking off any of the incoming soffit air.
Just make sure there is an adequate ventilation path from the soffit to the high roof (ridge) vents
If the foam vent channels are in place properly, that should be sufficient to prevent the soffit vents from being blocked.
But it doesn't hurt to double-check. The vent channel should "communicate" with the soffit vent below and come out above the level of the insulation on top. Should not be significantly crushed by the insulation. Every soffit vent should have a channel.
You can blow in as much insulation as you want, so long as you don't block the vents. The more the merrier.