I just had a gas insert installed into an existing chimney. We found out (via a long, irrelevant story) that the exhaust vent goes all the way to top of the chimney where it is capped (as it should be), but the intake vent only goes up about 4 feet and dead ends into the chimney cavity... is this right? All of pictures in the manuals say that it needs to go to the top, but the installer says this is fine and to code... any thoughts on this?