Is there a good way to cut foam insulation? (Pink Owens-Corning type)

I need to cut some to install a portable AC. Every time I do it, no matter if I use a bread knife, butcher knife, hack saw, whatever, I always end up with pink foam everywhere. Any tips for this?

I've done some work with a hot knife that has gone well, but the blades tend to be on the short side, so a little tedious.  Last time I had to cut large sections out, I used a brand-new razor knife like the big one in this picture:

You'll get some shavings, but it's usually not too bad.

(Oh, and using a torch to heat the blade in the plastic razor knife might seem like a flash of brilliance but that feeling will only last until the handle of the blade starts to melt...)

I can't find it online, but I have a simple plastic sheath of sorts that fits standard utility knives. It's hard to describe, but the sheath compresses the batting so that you get a nice, clean cut every time. It's simple and cheap, and I found it in the insulation aisle at Lowes Depot many years ago.

Score it with a razor blade and snap it. 

You're talking about the hard foam? How thick?

I'd probably just use a hacksaw but I'd do it outside over the trash can.

I always use a utility knife. It'll cut through the 1" thick stuff ok, if it doesn't make it all the way through just snap the board at the line.

The pink rigid foam stuff. I haven't decided how thick I'll be using. I did this once before where I  used whatever the thickest we could get--I want to say it was over 2 inches--because it was going in a sliding door and needed to be really strong. This stuff is just going in a casement window, so I'll probably use 1 inch or less. 

Ah, I missed the "foam" part. Yeah, I usually score and snap with that. You get a little debris, but it's not too bad.

Hot wire? 

Tom_Spangler said:

Ah, I missed the "foam" part. Yeah, I usually score and snap with that. You get a little debris, but it's not too bad.

This. I’ve had the best luck with scoring and snapping

I used a razor blade and snapped it when I trimmed panels to fit the garage door.