A minimally invasive method of adding thermal mass to a building is to apply Phase Change Material (PCM) to the interior of the structure. This paper describes a simulation-based approach for informing the integration of PCM in high performance homes without mechanical cooling. The analysis considers phase change transition temperature, quantity, and location of PCM within the building. The effectiveness of each test case was determined based on the number of hours that the indoor conditions were outside the ASHRAE defined comfort zone. Results showed that for most climates a PCM melt temperature of 25°C yielded the largest increases in occupant comfort; however the magnitudes of increases in occupant comfort were highly climate dependant. Reductions of 93% of zone-hours and 98% of zone-degree-hours outside the thermal comfort were achieved for simulations in Portland, Oregon. However, reductions of only 6.4% of zone-hours and 7.3% of zone-degree-hours outside the thermal comfort zone were realized in Phoenix, Arizona.