People spend in industrialized countries more than 90 % of their lives in an artificial indoor environment (home, transportation, work). This makes the indoor environment much more important for people health and comfort than the outdoor environment. In typical office buildings the cost of people is a factor 100 higher than energy costs, which make the performance of people at their work significantly more important than energy costs. The task is to optimize indoor environmental conditions for health, comfort and performance while conserving energy, since more than one third of current global energy consumption is used to maintain indoor environments. Detailed field investigations of the indoor environment in hundreds of large office buildings in many parts of the world have documented that the indoor environmental quality is typically rather mediocre, with many people dissatisfied and many suffering from sick-building syndrome symptoms. Recent studies under laboratory conditions and in the field have shown a significant influence of the indoor environment on people’s productivity. Also studies on people sick leaves show a very high loss of work time and performance, which have significant economic consequences for companies.

The paper presents an update on today’s requirement for a healthy and comfortable environment. The paper will mainly be dealing with the indoor thermal environment and air quality. Several standards and guidelines are specifying requirements related to comfort and to health; but the productivity of people is not taken into account. Recent studies showing that comfortable room temperatures, increased ventilation above normal recommendation, reduction of indoor pollution sources and more effective ventilation increases the performance of people. The results indicate increase of productivity of 5-10 %. Also based on the laboratory studies a 10 % increase in dissatisfaction decreases the productivity with around 1 %.

Today an acceptable indoor air quality is mainly defined by specifying the required level of ventilation in air changes per hour or the outside air supply rate. This would be equivalent to defining the requirements for thermal comfort by specifying the level of heating or cooling in Watts. The increasing societal need for energy efficiency will often result in very tight buildings. This means that the amount of outside air supplied by infiltration is not enough to provide the required ventilation. In some standards, the required ventilation is based on adapted people (occupants) while other standards refer to un-adapted persons, who have just entered a room. Which approach is correct? Or should it depend on the type of space or occupancy? Furthermore, the level of ventilation will depend on the criteria for acceptability, like health, comfort (perceived air quality) or occupant performance. The required outside air supply rate will be the same or higher than the required ventilation rate depending on the ventilation effectiveness. Existing standards do not or only in a limited way acknowledge the use of air cleaning as substitute for outside air. Furthermore, the concept of demand controlled ventilation is in many cases not taken into account.

The present talk provides an overview and discusses the criteria used for specifying required ventilation rates, and suggest ways of meeting the criteria in a more energy efficient way by means of improved ventilation effectiveness, use of air cleaning and by means of demand controlled ventilation.

Recently the international media like in USA, Canada, UK, Denmark, Germany etc. has been discussing the issue of differences between men and women regarding thermal comfort and the preferred room temperature.

Fanger (1982), Fanger and Langkilde (1975), and Nevins et al. (1966) used equal numbers of male and female subjects, so comfort conditions for the two sexes can be compared. The experiments show that men and women prefer almost the same thermal environments. Women’s skin temperature and evaporative loss are slightly lower than those for men, and this balances the somewhat lower metabolism of women. The reason that women often prefer higher ambient temperatures than men may be partly explained by the lighter clothing normally worn by women.

First, the primary reason is that we are overcooling buildings in summer, using enormous amounts of energy, and creating uncomfortably cold conditions for everyone. A study at Lawrence Berkeley National Laboratory found that average temperatures in office buildings in the U.S. are colder in the summer than in the winter (exactly the opposite of what they should be), and are actually lower than the minimums recommended by the standards. Existing international standards like ISO EN7730, EN15251 and ASHRAE 55 are based on the same basic studies described above. These standards do not specify different room temperatures for women and men when doing the same work and dressed in similar clothing. Contrary to what has been suggested, these standards are not devised exclusively for men. They are based on extensive laboratory studies of both men and women wearing the same clothing, engaged in the same activity, and exposed to a wide variety of thermal conditions (air temperature, surface temperature, humidity and air movement). Metabolic heat production was simply a proxy for the kind of activity. And while it is one of many variables used in an empirical formula, it is not an input to a heat balance equation, as one might find in a thermo-physiological model (which exists, but was not the basis for the standards). The primary reason is that we are overcooling buildings in summer, using enormous amounts of energy, and creating uncomfortably cold conditions for everyone.

Alternatively to full air-conditioning heating and cooling may be done by water-based radiant heating and cooling systems, where pipes are embedded in the building structure (floors, ceilings, walls) or in the center of the concrete slabs in multi-story buildings. The present talk will discuss the possibilities and limitations of radiant surface heating and cooling systems. Differences in performance and application of surface systems compared to embedded systems are presented. Results from both dynamic computer simulations and field measurements are presented.

The paper shows that for well-designed buildings these types of system are capable of providing a comfortable indoor climate both in summer and in winter in different climatic zones. Various control concepts and corresponding energy performance are presented. To remove latent heat, these systems may be combined with an air system. This air system can, however, be scaled down with the benefit of improved comfort (noise, draught) compared to full air-conditioning. An added benefit can be reduced building height due to the elimination of suspended ceilings. Finally, surface heating and cooling systems use water at a temperature close to room temperature. This increases the possibility of using renewable energy sources and increasing the efficiency of boilers, heat pumps and refrigeration machines.