The top and bottom components of a truss rafter are called the top and bottom CHORDS. The connecting pieces that attach the top and bottom CHORDS are called webs. Trusses are engineered to perform dead load support and have not been engineered to support additional loads of " storage items" that a home owner may want to add. If excessive weight is added to an existing truss structure that has not been engineered for the load, problems MAY occur. Good luck.
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Originally Posted by tooski
Just a diy'er. I insulated two new builds I've lived in, a couple of garages, and renos on rental properties. I've only ever used batt insulation. My place in AZ has blown in the attic. I hate it when I have to go up there. I can't move around without fibers floating around. Once installed, it's not a problem with the batts. Rolls are basically the same, just one long roll cut to length as opposed packaged bats with a specific length and width. Easier to handle than cutting up a long roll. Generally speaking a 6" bat is R20. Put them in a 2 x 6 (5 1/2) wall stud space and it's R19. You can buy a R20 or R22 for that 5 1/2" but a bit more expensive. In the ceiling, you are not governed by lumber width. 8' thick bat is about R30, 11" is R40. Code in my area requires R40 minimum. Bats usually come in either 15"or 23" widths. If you live in a older house with constructed rafters they may be 2 x 6. I've not seen more than 2 x6 rafters. Modern manufactured and engineered trusses are usually made with all 2 x 4's. Any truss company will use the dimensional lumber you request. I've had a couple built with the horizontal piece built with 2 x 8 so I can put install an 8" bat (garage) and put an osb 'floor' on top and not crush the bat to a thinner (ie less R value) thickness. Btw all the lumber sections in a manufactured truss are called 'cords'. I have seen trusses with some of the cords made with 2 x 3's, obviously to save money.
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