THE CLASSIFICATION OF THE INDOOR ENVIRONMENT
Measuring comfort to increase well-being, productivity, and energy savings
To express the quality of an indoor environment (IAQ Indoor Environmental Quality), it is necessary to consider several comfort parameters together and define them already in the design phase, because they will influence the energy consumption of the building.
Think about the room temperature set in winter: the higher it is, the more energy consumption for heating increases. But on the other hand, some buildings require more attention to comfort and this need cannot be ignored.
The UNI EN ISO 7730:2006 standard proposes design criteria for the indoor environment based on some assumptions (for example: clothing index of 0.5 clo in summer and 1.0 clo in winter), for different types of spaces and different comfort categories.
The UNI EN ISO 15251 standard instead provides the methodology for evaluating environmental quality (understood as thermal comfort and indoor air quality) through numerical simulation throughout the year, or through measurements made over a long period (Annex I). The main parameters to be evaluated in these investigations are the temperatures in the environment, hourly exchanges and/or CO2 concentration.
MEASUREMENT CAMPAIGNS AND QUESTIONNAIRES FOR THE EVALUATION OF THE INDOOR ENVIRONMENT
When you want to characterize an existing building from a comfort point of view, in addition to the measurement campaign, it is equally useful to approach a study based on the subjective response of the occupants. By interviewing a significant sample of people, it is possible to get a picture of the situation of a building and highlight the major problems to be solved through improvement interventions.
Furthermore, through questionnaires, it becomes possible to characterize the environment also in relation to visual comfort and acoustic comfort: once the criticality has been identified, it will be possible to measure and quantify the discomfort with the appropriate tools.
The EN 15251 standard addresses the issue of questionnaires (Annex H), defining the methods of delivery and indicating some examples of questions. Among these, the one on thermal sensation (from hot to cold passing through neutrality) is certainly fundamental to understand the situation.
The questions can vary depending on the type of study, as can the setting of the questionnaire. If you wanted to understand the adaptation of people subjected to the same environment for long periods, you could submit the same questions about the perceived thermal sensation at intervals and analyze how these values change. This method was adopted, for example, during a study that involved a significant sample of people subjected to various air conditioning systems for a period of three hours during which they were performing sedentary activities in the office.
Conversely, if you wanted to evaluate the quality of a particular transition environment, the length of stay could be variable and the perception of comfort would change a lot from the type of clothing and the activities immediately preceding. The Energy Efficient Building (EEB) group of the Institute of Renewable Energies of Eurac in Bolzano recently conducted a study on the perception of comfort in transition spaces within shopping centers during the summer period, trying to evaluate, also with questionnaires, whether for the purposes of energy saving it is possible to increase the set point temperatures normally adopted while maintaining the comfort conditions for the occupants.
CONSEQUENCES OF A BAD ENVIRONMENT
The consequences of a bad environment within workspaces not only affect health, but also productivity and generate an increase in costs. Obviously, the opposite is also true: investing in the quality of the internal environment brings benefits in terms of productivity and for this reason there are countless studies that deal with these issues. Through the observation of reaction times and the productivity of people working in an office, Finnish professor Olli Seppänen was able to correlate the increase in productivity with the increase in the amount of ventilation air per person, demonstrating that doubling the air flow would also improve by 1.5%.
Through a study that involved 56 buildings throughout Europe, it was shown that going from a percentage of dissatisfied people of 60% to one of 25% leads to a productivity increase of 3.4%.
The REHVA Indoor Climate and Productivity Guide 2006 reports some methods to evaluate the goodness of the investment aimed at improving the internal environment taking into consideration:
- the value of work (average salary)
- the concentration of people (expressed in m2/person)
- the expected productivity increase for the improvement of the internal climate
- the interest rate.
For example, it is shown that with investments of about €270/m², a return can be achieved in about 10 years, with productivity increases of 2%.
Another aspect that is extensively discussed is the quality of the indoor environment in school buildings. As it concerns the health and learning ability of the new generations, there is a growing awareness of the problem and a greater commitment to try to solve it.
The Ministry of the Environment has published an informative document presenting the state of health of Italian schools and proposing a series of easily implemented preventive measures, such as air exchange and the use of ornamental plants capable of reducing indoor pollution.
Inside, the results of the European Multicenter Project SEARCH (School Environment and Respiratory Health of Children) conducted simultaneously in six European countries, including Italy, from 2005 to 2009 are reported. Environmental assessments of the selected schools were carried out through questionnaires, indoor-outdoor environmental measurement campaigns, and assessments of children’s respiratory health.
In Italy, measurements were made in six regions, from north to south including the islands, and they highlighted frequent symptoms of respiratory diseases, asthma, and allergies, which often result in absences from school.