Be warned! - Element Armor is itself damaged by stuff like lava (many of us consider this a 'bug', or at least an "anti-exploit").
So be careful: if you leave stuff like that on too long while traversing lava, while you won't take HP damage, the armor will, and could eventually be destroyed.
He's talking about the spell, not pants and boots with elemental resistance. It's great to find a helm, gloves, chest, and belt with elemental resistance, because then you hardly need the spell. Even with the spell, you need to follow Randomizer's advice and remove boots and pants before wandering across lava.
And, next time you're looking for spells, don't forget to check the innkeeper in Durnore. She keeps a lot of good ones on hand.