If five people with the exact same genes each live in different environments what's the heritability?

No, no, it's higher than zero! I've seen twins (personally) who were separated at birth and when they meet, there is an astonishing amount of similarities. Weight gain is the same, hair style the same, even the casual or sophisticated dress is the same. The two I've seen were brought up on different continents and each were introverted, each were creative, and each were high on the scale of sexually alluring! (I dated one of them when they first met each other....Owww Momma)!

The previous answer is correct - the heritability of WHAT? The heritability of schizophrenia? The heritability of alcoholism? Heritability is a statistic about the interaction of genes and environment across groups on SOMETHING.

What's the heritability of WHAT?

Whatever you're asking about, I doubt the heritability is zero.