Only one Heaven exists.

Two Heavens do not exist.

Two heavens may exist, if and only if each heaven is not the true Heaven.

For the reason that there is only one true Heaven, and there are not two true Heavens, the true Heaven is a proper noun.

If you believe that every proper noun should be capitalized, and if you are referring to the one true Heaven, then you must spell the English word which is spelled with the English letters h, e, a, v, e, n, in that order, as Heaven, with an uppercase H, in order to be consistent with your own beliefs.

If you do not believe that every proper noun should be capitalized, why are you asking whether or not to capitalize Heaven?

If you are not referring to the one true Heaven, what are you referring to, and why would you refer to another heaven that is not the one true Heaven? Are you trying to tell me something false? If so, you had better not tell it to me! May the Lord God, Jesus the Christ, the Messiah, Yehoshua Ha-Mashiach Ben Yehovah Elohim, be with you! Amen.