The purpose of this study is to quantify the impact of insulation of various parts of building envelopes on building energy consumption. Using eQUEST, a series of parametric simulation was conducted to acquire building energy consumption data for a range of R-values of walls, roof, and windows of a typical two-story single-family home in the U.S. Two climatic zones were applied in simulation: Detroit, Michigan and Miami, Florida. Analysis was conducted for annual heat gain and loss, and benefits of insulation value of walls, roof and windows respectively. In addition, analysis of heat gain and loss components was conducted for the purpose of identifying strategies for effectively installing insulation on different parts of building envelope.