The three sources
Amortization is the quiet one. Early payments are mostly interest, and the principal share grows every month, so equity from paydown accelerates over time.
Appreciation is the loud one, and it is outside your control. Improvements are the selective one, since only some of them return what they cost.
What actually adds value
Kitchens, bathrooms, usable square footage, and systems that a buyer would otherwise have to replace tend to hold value. Highly personal finishes and features that outpace the neighborhood rarely return their cost.
Before a large renovation, ask what the finished home would be worth relative to others nearby. The ceiling of a street is real.