how do you mean by "gutting" ?? there is a expanding foam/spray on method that is supposed to be effective, but it requires tearing off the drywall. there used to be ways of doing it with a similar expanding insulation but it was pumped in through small holes in the exterior of the house that were easily patched. as yours is brick, that option(if it still exists) wouldn't work unless its possibly to do it from the inside. really there is nothing that i know of that doesn't involve some sort of "gutting" or re-cladding the exterior.