The prescriptive requirements of SB-10 state that exterior opaque swinging doors are required to have a U-value not exceeding 0.4.  This new requirement will go into effect January, 1st 2012.  Fleming  says that Trio-E is the only steel stiffened door on the market today that exceeds compliance with the new SB-10 supplement.  

The Trio-E door is steel stiffened for strength, but has achieved an operable U Factor of 0.29 which is 50% better than other steel stiffened doors currently available on the market today, according to the company (the lower the U factor the better the insulation).