If you don't want to loose ceiling height, you will need to remove the celing covering to gain access to the floor joist cavities.
A product we've had great sucess with is Roxul (http://www.roxul.com ... read more
Like everyone else has mentioned you have to do your due diligence in securing a high quality contractor. However, you the client may want to switch the context of the question. If you are implying th ... read more