ok, I want to take out some of the single pole breakers and replace them with tandum breakers. can I replace all of the single pole breakers with tandum or is there a limit?
I agree with bennie, install a sub-panel 200 amps is a big service, speaking in residential terms. By the way how many sq ft is your house it may be time to upgrade the service.
Get a 100amp rated MLO panel 8/16 circuit/space, install a 70amp breaker to protect the sub-panel, you will have to make room for the 70amp brk. in the main panel, so keep in mind, you will have to relocate (2) two exsisting circuits from the main panel to your new sub-panel, and now you have some room to install your new cicuits, of course if it is a major remodel, you may have to upgrade to say, a 320amp service, this will allow you 200amps for exsisting electrical and 100amps for future additions, it all depends on you and $$$.