In 1994, ASHRAE began developing a guideline for measuring retrofit savings (GPC-14P). In support of Guideline-14P, ASHRAE initiated RP-1050 to develop a toolkit for calculating linear, change-point linear, and multiple-linear inverse building energy models. The resulting Inverse Modeling Toolkit (IMT) can be used as part of a procedure to measure savings. This paper describes the numerical algorithms used to find general least squares regression, variable-base degree-day, change-point, and combination change-point multivariable regression models in the IMT, as well as the equations used to estimate the uncertainty of predicting energy use for the purpose of measuring savings using IMT models.

Units: Dual