Fire alarm need to be hardwired?

[Aref Shehadeh]

Rewiring most of a house I'm flipping due to it containing knob & tube. Taking down a load-bearing wall and redoing some of the ceiling on the first floor. The house was built in 1930. Fire code states if a house was built prior to 1976 it can have battery operated smoke detectors. New construction required hardwired or wireless interconnected systems. 

Does a rehab qualify as new construction in the eyes of fire code? Guess I'm asking if I can get away with just using battery smokes or would I need to upgrade the whole house. Going to call the fire department but wanted to extend the question here first.

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[David Clay]

Originally posted by @Paul Maretzky:

Most towns will want you too bring certain things up to present code during a renovation. When I renovated the second floor of my home, I had to hard wire the entire house for smoke detectors. Check with your fire inspector first. Plus its a nice little thing to throw in when you go to sell.

I was thinking that very thing. If going to the expense of a total rewire is it really that much extra to put in wired SD's? I don't know, but in relative terms I would think that it wouldn't be that much extra. Also, depending on the cost of the rehab (which sounds expensive) I would think that the end buyer is going to see that and think that "everything" has been updated and the house is totally modern. Big selling point in my opinion. Besides, IMO battery operated SD's are a pain in the tush.