Earth–air heat exchangers (EAHE) help heat or cool a building by coupling the ventilation system to buried ducts. Recent efforts have been trying to increase EAHE performance by improving the thermal properties of the region around the pipes; however, they usually miss connecting its size and shape with efficiency (θ) and thermal potentials. This paper studies EAHE with ducts surrounded by galvanized structures. We consider different layouts, using circular blocks and rectangular ones with at most four fins. Since the arrangements have high thermal conductivity, they increase θ to almost 95%. Besides, they allow reducing installation size by nearly half, keeping θ above 70%. However, we also show the drawbacks of this method. Among the results, we see that using only one fin is sufficient to increase the EAHE thermal potential (Pt) by 33% relative to a conventional installation, but using them carelessly can reduce the soil thermal potential (Ps). We show that circular shapes increase θ, but they have a poor effect on Ps as their sizes increase. Finally, varying the size of a rectangular structure with no fins, we obtained the best result, i.e., θ close to 95%, Ps and Pt increased by 25% and 60.5%, respectively.