Ooooh........THIS isn't too good...........:shrug:

[warthog]

Just the other day,I decided to take a hike into the upper abyss also known as the attic,to check things out.Looked good,actually:Nice and dry,not too messy-and not a drop of insulation in sight...Turns out the lovely Mrs. Phelps told me her last husband insulated the walls real good re-doing this house,but didn't get to the attic before he got sick.Explains the ice dams at the roof edge,not having enough ventilation up there,too(I found a big vent at one end of the house completely blocked off)......SO:being that this effectively is the fifth house I have owned,Warthog 'Bob Vila' Steve seized the opportunity,and immediately made plans to blow some insulation in this Spring.Called one guy,he uses that spray foam stuff,quoted me in the $2,000.00 range,then I called a blown in insulation guy,gave him my square footage,want it 6 inches deep.Total price for all of it,including the blower rental,other things needed up there and hiring two guys to do it,will be about $400 clams,and I get to play supervisor.Goodbye,ice dams....I told Marcia that next winter,we will be able to turn the furnace down to 40,and wear shorts all winter long.......SURE........

 

[Sandtick]

I would go deeper then that.
My family just had a cottage rebuilt and they blew in well over 20" of insulation.

 

[Steve O]

You have to keep the attic above the insulation, cold, so the roof snow doesn't melt, running down to the top of the colder overhang, then freezing...blocking (damming) the melt flow...then backing up under the shingles.....leaking into the living space.
Find out what the minimum 'R' value in your area for an attic floor should be....there are zone charts available on the net (make sure they are current), or, call your township for the min code requirements for your area.
Stay at or above the minimum thickness...above is better.
Ventilation is a must for the attic to breath out any vapor and to keep shingles cooler in the summertime.

 

[Ma Betty in MO]

You are so fuuunnny steve, putting your thermostat down to 40 and wearing shorts in the Winter weather of Michigan doesn't seem logical to me! Ma