You could have an excellent site assessment and an appropriate cost effective design for a system, for which you have paid good money, but all this is wasted if the attention to the detail is ignored when the system is being installed. It does not matter how experienced your Builder is or how many houses they have built, up to 80% of existing systems have some issues. Ideally whoever is going to certify your system should engage with the installer prior to any work commencing. No work should be carried out without supervision or covered up prior to inspection. This process is similar to a chain, if one link breaks down, the process fails. Remember in such an instance the problem becomes yours.