This paper proposes an optimum pipe material (PVC vs. PE) design & selection for open loop ground heat exchangers. Heat exchange efficiency and/or workability, and the need for trench insulation were investigated by comparing EWT (cooling mode) of each system. CFD simulations for the PVC and PE pipe with the same inner diameter show similar EWT. This is because the PVC pipe has a small thickness but a low thermal conductivity as compared to the PE pipe, and thus these two properties tend to offset each other. However, a hypothetically insulated pipe led to a meaningful drop of EWT. This means pipe insulation is of importance in performance of ground heat exchangers. From analyzing climate data and system operation, it is not advantageous to insulate trench pipes due to construction difficulties and ground temperature characteristics that are seasonally varied.