Green building standards like the Living Building Challenge promote the construction of net-zero energy buildings. In order to meet these standards, alternative heating and cooling methods become necessary, especially for designs with high glazing percentages in temperate climates, such as for aesthetic purposes or use in greenhouses. The design and analysis of a low-cost heating and cooling system is being investigated to address these scenarios. Air-source heat pumps are now commonly used in super-insulated, net-zero energy building designs, and we explore the possibility of augmenting this configuration with an inexpensive seasonal thermal energy store to address the increased heating and cooling loads. A high-glazing building scenario was modeled in Revit to establish monthly loads for a proposed building design, and a heat transfer model of a thermal store coupled to a heat pump was simulated in COMSOL Multiphysics to test feasibility of this idea. The results suggest this strategy has potential but may be limited in application due to its large size.