Reduction of infiltration in the Equinox House, a residence under construction in Urbana Illinois, has been characterized through a series of blower tests as different joints and seams in the building were sealed. Equinox House is constructed with 30 cm thick SIPs (Structural Insulation Panels) wall and roof panels consisting of a Styrofoam core and oriented strand board sheathing on interior and exterior surfaces. Blower door tests were performed as each type of seam in the house was sealed. Wall to foundation connections, wall to roof connections, panel to panel connections, and miscellaneous gaps were examined. The effect of adding wall surfaces (drywall) to the building are also presented. The results show strong correlations between level of infiltration and the amount of labor and the amount of sealant used to lower the infiltration. The house infiltration was reduced to 0.37 ACH at 50 Pa. The correlation parameters, while specific to this type of construction, demonstrate how costs related to infiltration reduction can be formulated and utilized for optimal building design analyses.