Ideally, you want to have the company that you hire be the company that actually installs the work. It is a challenge to manage the quality of an outside company. Sub-contractors may not follow the same safety precautions, installation standards, and quality procedures that the company you hired does and they may not offer the same warranty and reputation of installers. As a result, the home owner may not be receive the quality and service that they deserve. Sub-contractors are usually required to arrive at the job in unmarked vehicles or slap on a temporary magnetic sign to their vehicles.