insulating 4" space with 2" insulation and airflow

[effi]

i'm looking for some 2" or thinner fiberglass insulation bats or blankets, preferably 24" wide and with aluminum foil facing on one side

where can i get 2" thick fiberglass insulation?

it doesn't look like the big manufacturers, owens-corning, johns mansville, etc. make any, based on their websites

[default]

You probably can't. Either use foam board, or squash 3.5" glass down with whatever you're using as ductwork.

--Goedjn

[William W. Plummer]

Compacting fiberglass insulation destroys its insulating properties. You can cut it with an electric carving knife to make it thinner.

[effi]

okay here's the rub, owens-corning makes it,

supposedly does not sell it retail, only available to contractors (whatever that means), and here i thought home depot and lowe's had everything...