Titan has a base temperature of -196. 4°C, which is 76. 6K. With its albedo of 1. 00, fixed by not having hydrosphere, you can get at most a surface temperature 3X the base temperature (in K), which is 229. 8K or -43. 2°C.
Considering the default human species having a base temperature of 22°C with a range of +-22°C, you would need either "Base Temp -40C" and "Temp Range +4" (to get to -18°C +-26°C) or simply "Base Temp -50" (to get to -28°C +-22°C). That brings the total research cost to 155k and 160k RP, respectively. Edit : Plus designing the new species itself, which can be several thousand RPs.
Unless there's something I don't really get in new species (never done it myself).