How should I know any of that? I'm still busy designing NUBE's logo! Although, if we were to have lunch at a place which was cognizant enough of our needs to provide copious napkins, I would guess that one way to accomplish the goals of which you speak, would be to accrete, around the Earth, a solid shell consisting of asteroids, with plenty of space between the planet and the shell. The planet's surface would be heated due to a combination of the heat which escapes the core, and through the use of nuclear energy, in some fashion, because both of those sources would be trapped by the shell. The shell would obviously protect from space debris, and less obviously, due to its thickness and density, it would protect from the radiation likely to be encountered in deep space.

AsteroidShell = 3For1Deal!