What I was trying to remember is a product called Icynene. It's much more expensive than fibreglass but not so bad as spray-in systems go. It's more effective than most spray-in systems - it's possible to retrofit an old house to be as airtight as modern-construction, with all the good and bad of that - and it has the added benefit of being a not-too-bad soundinsulator as well. I found it rather effective at helping dampen road noise at Murkworks South, particularly when combined with better windows.
Anyway, hopefully one of you were the person asking. ^_^