I have an analysis for a real estate project done and I'm changing the discount rate but IRR is not affected. I don't understand why this is...? It seems that changing the discount rate would change the NPV, changing the point where NPV=0.
Because the IRR doesn't depend on discount rate.
Instead, the IRR is a discount rate.
The IRR is the discount rate that makes the NPV=0.
Put another way, the IRR is the discount rate that causes projects to break even.
Raising or lowering the discount rate in a project does not affect the rate that would have caused it to break even.
If you have a schedule of discount rates then the IRR you seeking is the interest rate at which net present value of the investment discounted using a schedule of rates is the same as the net present value of investment using a single rate. Think of this a interest rate shocks over the term of the investment and the investor is seeking a single rate that will offer the same return on investment as those offered by the schedule of discount rates.
See these two links