Insulation width

[wilkrod]

HI all,
I want to start insulating my garage in the next few weeks.
Only need to do the overhead which is 2'X4' truss 24" o.c.
I already decided to use owens corning kraft faced with the paper wings to secure to the sides of the truss.
My silly question is : Would it be best to get the 24" wide rolls, or is the 23" width sufficient?
Thanks for the advice.
Jeff

 

[87jeepwrangler]

fiberglass insulation is only effective if it is touching along the length of the joists. if there is any space, you are loosing almost all of your insulation value in that bay.

 

[Muttly]

your joists are on 24" centers, the 2x4 is 1-1/2", 23" insulation is the correct product.

24" insulation is for steel studs.

Most important, how thick?

 

[Falcon67]

"24 inch on center" leaves 22 1/2" between the joists.

 

[brass89]

Ditto on the above posters, 23" will give 1/2" extra to ensure a complete coverage fit between the rafters/top cords. Part of the way fiberglass (fluffy) insulation works is utilizing trapped air spaces between the fibers, so you don't want too much extra overlap that would result in compressing it to fit. That would lower the insulation ability. When putting it up, just do your best to get it even between the rafters. Since it's a soft material it could get accidentally shoved too far to one rafter or the other and leave a gap along the edge. Good luck with your project.

 

[Nowater]

A layer of plastic or something else will help with air sealing. Air sealing is very important!