Shredding fiberglass scraps
When installing bats of fiberglass insulation one usually ends up with scraps of various odd sizes, that cannot be cut and fit further. Rather than dispose of this material I have experimented with improvised hand tools to shred or chop it up and to use it as a loose or pour-in insulating material. I have had limited success but have found that shredding it into a uniform consistency with good R-value is possible.
Chopping it tends to make it clumpy, which decreases the ability of the material to hold small air cells.
I would like to know of any “mill” that would process such scraps in an efficient enough manner to make this feasible. I think that it would save much petroleum feedstock and energy if this recycling was available to home builders and DIY’ers.
Oldogwalker
Replies
I used my scraps for: filling/stuffing small gaps around doors, windows, and other odd places ... overstuffing ... as long as it FILLS the cavity is way OK (energy wise) and for sound insulation around bathrooms and such other areas you wish to reduce sound transfer. I threw nothing away at all. I wouldn't shred/chop it ... just use it ... no effort and no flying fiberglass in the air. Just one point of view.
I appreciate the uses of scraps for filling small and tight spaces, but I have bags of scraps left over from commercial construction. There are uses for pour in insulation, such as cavity walls in retro projects. I note that compressing fiberglass reduces is air-holding capacity and any cavity left unfilled across a temperature gradient will induce a (perhaps tiny) convective air current that pumps heat to the cold side. Cellulose loose insulation has less insulation value, absorbs water more and is denser, causing it to settle more, than the fiberglass we get in bat insulation. Thanks for the response.
I'd still use it to fill walls for sound batts. If nothing else cut narrow pieces the width of the stud and stack them up.
Don't understand your comment about compressing. If you take e.g. two R-11 batts and fill a 2x4 wall cavity ... You won't get R-22, but you will get a LOT more than R-11. If you take a batt and compress it, it gives you less R-value, but if you fill up a cavity, you will improve overall thermal value of that wall thickness. Compressing it gets rid of small cavities and makes even smaller air spaces ... and that is good ... as long as you fill the cavity.
If I were trying to make a shredder I'd attach several circular saw blades to a common shaft, make a "comb" to fit between the blades, and the feed in the fiberglass while turning slowly.