The FHA Streamline Refinance is a special mortgage product, reserved for homeowners with existing FHA mortgages. FHA Streamline Refinances are the fastest, simplest way for FHA-insured homeowners to refinance their respective mortgages into today's mortgage rates.
The FHA Streamline Refinance program's defining characteristic is that it does not require a home appraisal. Instead, the FHA will allow you to use your original purchase price as your home's current value, regardless of what your home is actually worth today.
Another big plus is that FHA mortgage rates are the same in the FHA Streamline Refinance as with a "regular" FHA loans. There's no penalty for being underwater, or for having very little equity.
excerpt taken from The Mortgage Reports by Dan Green