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HFC-365mfc and HFC-245fa are now well documented as promising blowing agents, and their production will come on stream in a few years. However, none has the same ideal boiling point as CFC-11 or HCFC-141b. Blends may offer the best compromise to customize the different end-use requirements. Two different directions for further developments have emerged from our work: Two binary, non-azeotropic blends of HFC-365mfc with HFC-245fa or HFC-134a open the door to non-flammable blowing agents with a convenient boiling point in the range of 20 to 25°C (depending on actual composition) and a very good gas phase thermal conductivity. These new blowing agents could be safely used in the same manner as CFC-11 or HCFC-141b, but would be the most expensive option in the series of blowing agents currently under examination. It would fit the needs of foamers looking especially for non flammability (ease of handling, low investments) and optimized foam thermal conductivity. Three low boiling, binary azeotropes have been found with HFC-365mfc and the three pentane isomers (n-, iso-, and cyclo-pentane). Although these azeotropes are flammable, they open the door to more cost effective formulations with improved properties over formulations blown with straight pentane. It is anticipated that each mixed blowing agent now under investigation will find applications in specific end-uses. HFC-365mfc appears to be a key building block to design a full range of blowing agents which offers a wide flexibility to system houses and polyurethane foamers, both in the direction of non flammable or flammable blowing agents. Semi industrial trials with the blends and industrial trials with straight HFC-365mfc are reported as a practice related example of the suitability of these blowing agents.