Buildings were originally constructed to protect us against a hostile environment. However, the goal of energy and cost reduction means that the opposite is now true: high-tech insulation materials, optimisation of the use of floor space and a high user density result in falling costs. Until now, however, little attention has been given to the consequences this has for health. From ventilation and the ideal air humidity through to filters, light and the right choice of materials, this section identifies effective measures to make buildings healthier. It also identifies the possibilities available for an in-house risk assessment. For complaints and symptoms caused by dry air, systematic communication within companies can be the prelude to initiating solutions to improve the indoor climate.