ok.....here is what you do.
step 1 - go to the dollar store and pick up either a measuring cup that will measure a litre, or a pail that has litre measurements on it
step 2 - go to walmart and pick up a bigass box (or several) of cheap cat litter. In my case, I get the normal cat litter that we usually get to avoid having to buy it later.
step 3 - measure out a litre at a time (or several litres if you have a big enough acturate container like a water pail) and keep track of how many litres you have.
step 4 - go to
http://www.onlineconversion.com/volume.htm and convert to cubic feet.
step 5 - dump cat litter back into bag or another container and use it to help clean up all that left over fiberglass resin (or beer) that has spilled on the garage floor
note - another great reason to use cat litter instead of packing peanuts is if you have to go tinkle, you wont have to go far, and it almost cleans itself up.
I did this recently for an enclosure and it works great because since it is fairly uniform in size and fits in all areas and crevises extremely well. Plus if you push on it once its in the enclosure it wont compress down like packing peanuts.
Hope this helps