Increased evidence shows that indoor environmental conditions substantially inﬂuence health and productivity. Building professionals are interested in improving indoor environments and quantifying the effects. Macroeconomic estimates of nationwide gains have been developed. They show that the potential beneﬁts from indoor environmental improvements for the society are high (Fisk, 2000, 2001; Mendell et al., 2002b). Some calculations show that the estimated cost of deteriorated indoor environment is higher than the heating energy costs of the same buildings (Seppänen, 1999). Potential health and productivity beneﬁts are not yet generally considered in conventional economic calculations pertaining to building design and operation. Only initial, energy and maintenance costs are typically considered. A few sample calculations have also shown that many measures to improve indoor air environment are cost-effective when the health and productivity beneﬁts resulting from an improved indoor climate are included in the calculations (Djukanovic et al., 2002; Fisk, 2000; Hansen, 1997; Seppänen and Vuolle, 2000; Tuomainen et al., 2002). There is an obvious need to develop tools and models so that economic outcomes of health and productivity can be integrated in cost beneﬁt calculations with initial, energy and maintenance costs. The use of such models would be expected to lead to improved indoor environments, health and productivity. To systemize these buildinglevel calculations, we developed a conceptual model to estimate the costeffectiveness of retroﬁts of indoor environment. The model shows the links between the improvements in the indoor environment and potential beneﬁts. We quantiﬁed also the links between ventilation and sick leave, and high temperature and productivity. We also review evidence linking SBS symptoms with sick leave and productivity.