Heighten Spell and Dice Caps

[2bz2p]

Heighten Spell (Metamagic)
You can cast spells as if they were a higher level.

Benefit: A heightened spell has a higher spell level than normal (up to a maximum of 9th level). Unlike other metamagic feats, Heighten Spell actually increases the effective level of the spell that it modifies. All effects dependent on spell level (such as saving throw DCs and ability to penetrate a lesser globe of invulnerability) are calculated according to the heightened level. The heightened spell is as difficult to prepare and cast as a spell of its effective level.

Would a Fireball heighten to to 5th level have a maximum of 15HD based on the Dice Cap maximums for Arcane Spells?

[Tarik Blackhands]

No. If you want to raise damage caps you want Intensify Spell.

Heighten is just for leveraging higher DCs generally.

[blahpers]

No. The "dice cap" is a guideline for creating new spells, not a modifier for existing ones. You're looking for Intensified Spell. Good news--it only requires a 4th-level slot.