John, was this an AHJ or a house inspector telling you this? Unless of course you've some pretty severely amended one family members residential code, what they are telling you is not per IRC. In the UK (together with other portions of the EU), 'insulated' roller garage doors are available, http://emergency-garage-door-rep96172.newbigblog.com/9278589/residential-roll-up-garage-doors-prices-no-further-a-mystery