Indoor environmental quality in buildings encompasses air quality, thermal environment, acoustics, and lighting. While engineering and health sciences have studied the impact of these attributes on occupants, a limited number of economic studies have investigated their financial implications. However, the profitability of optimizing the indoor environment for real estate developers, investors, and tenants remains unclear. This ten-question paper summarizes existing literature on the economic value of improvements in indoor environmental quality. The first four questions summarize existing evidence, showing that these factors influence human performance, health, and well-being through different pathways, not all of which are sufficiently understood. The second part explores the economic value of optimized indoor environments and how economic research on energy-efficient buildings can serve as a suitable blueprint. This literature confirms that energy-efficient buildings provide a higher property value and offer a profitable investment case. However, to our knowledge, no research so far could effectively quantify the financial benefits of improved occupant productivity, health, and well-being due to an optimized indoor environmental quality, and how it could be used in a cost–benefit analysis to compare it with the rent and price premium tenants and owners need to pay for health-certified buildings. Existing studies on this topic often rely on indirect measures and lack direct evidence linking these improvements to objectively measured productivity or health outcomes. Therefore, this paper concludes with suggestions for future research to facilitate studies on the economic value of indoor environmental quality improvements and related healthy building attributes.