furnace makes economic sense, but that’s not always the case. Sometimes meager gains in efficiency don’t pay back the additional cost of a new furnace. In your case, however, replacement is probably a wise move. The boiler you’ve got now is as inefficient as they come, and might stop working any time now. If this were my proposed job, I’d ask any company providing an estimate for five customer references, then follow these up and talk to the homeowners. Has their new furnace performed well? Was the cost the same as the estimate? How long did the job take? Was the work accomplished with a minimum of mess? Asking for and following up references is a troublesome task that we shouldn’t need to do. It’s just that the reality of today’s trade world is such that competence, quality and honesty cannot be assumed.