Author: Kurth Tobias
Today, everyone is familiar with quality seals such as Minergie, Leed and Breeam. They stand for effective energy consumption, sustainable construction and optimal use of resources. So we rely on them when it comes to evaluating our everyday protective shell, the buildings and rooms in which we spend our lives. But do they also stand for optimal air quality in these spaces? This is a directly health-relevant question. Or formulated differently: Are these labels effective IAQ indicators or is their approach rather just green- or more precisely IAQ-washing? The article presented here attempts to answer this very question.
For example, when building houses with a higher Minergie standard, openable windows are often omitted. Of course, an efficient ventilation system can supply enough fresh air. This fresh air can be additionally filtered. In heavily polluted regions, often cities, this is a big plus. In the energetic ideal case, the latter even takes place via a heat exchanger.
Nevertheless, we know from our own experience rooms in which the indoor climate does not even come close to normal (halfway usable) outdoor air. (Doubters are cordially invited to an hour of ‘Building Energetics’ in the packed auditorium EPFL-CM4). In addition, after just a few years, bacteria, fungi, and other nasties can accumulate in ventilation systems, which have no surface to attack in a classic natural window ventilation.
With the continuously improving (=denser) building envelopes and a tendency to insulate – especially in the context of green-certified buildings – natural ventilation by convection is increasingly restricted. But let’s stay for a moment with our well-tried window ventilation: For optimal air conditions in a full lecture hall, for example, the air would have to be exchanged very often (rough estimation: every 15 min). In practice, this can hardly be managed. As a result, windows often remain closed for significantly longer periods of time, and air quality increasingly suffers as a result. The obvious solution, keeping the windows open permanently, is neither compatible with thermal comfort nor with the resulting heating costs, especially in the winter months. A mechanical ventilation system can therefore provide a very adequate remedy. In addition, the Green Building Standards, with their intended minimization of energy consumption, naturally have every motive to minimize mechanical ventilation, heat loss and costly filtration
It seems, that the problem of good indoor air quality in green certified buildings can therefore be reduced to the following question: Do the applied ventilation systems provide a sufficient indoor climate?
Emblematic is the study of Wei, Ramalho and Wandin according to which IAQ provides a section for 55 worldwide labels. In total, however, only 7.5% contribute to building schemes. Isn’t that a bit low? Again; houses primarily serve our protection and well-being. In the united states, the Environmental Protection Agency (EPA) has ranked indoor air pollution as a top environmental risk to public health. It seems we need to understand this pollution a bit better.
Indoor Air Quality can’t be measured in an absolute value. CO2 as well as the relative humidity are commonly used indicators. Furthermore the temperature is an important player in terms of felt comfort in a building. A non-sufficient indoor climate which also takes into account air pollutants such as formaldehyde and benzene can lead to various health-symptoms regrouped as sick-building-syndrome SBS. Based on this SBS term an US-study interviewed almost 150 employees in Green- and standard buildings. Although the indicated indoor air quality was similar in the two samples, it was found that the SBS prevalence is 15% lower in Green buildings. Other studies could prove better indoor air quality (based on CO2, humidity and VOC’s) for some Green Buildings, for other not.
The VOCs (volatile organic compounds) mentioned above represent an interesting group of pollutants in this case. Since some Green Building labels are based on building materials that emit particularly few VOC’s. Therefore, in this category, green building labeling actually directly improves indoor air quality.
In general, the issue presents a double-edged sword. On the one hand, green buildings, with their tendency to provide fresh air through ventilation systems, can provide much better IAQ. Clearly, their best performance is achieved in areas with already heavily polluted outdoor air. Mechanical ventilation systems can not only filter toxic pollutants, but also remove pollen pollution from outdoor air. Furthermore it can be easily combined with air conditioning or humidification systems. On the other hand, manually ventilated buildings require fewer materials, no ventilation-related energy, and are able to provide impeccable indoor air (at least in regions with good outdoor air). Nevertheless, they require some human effort and attention to indoor air, as well as regular opening and closing of windows, to ensure both good air quality and low heat consumption. For large (commercial, school, public) buildings, this may not be very suitable, and a well-planned and well-used mechanical system is likely to provide more performant results.
The best solution is therefore to consider effective IAQ labels in addition to sustainable and green building certificates. Such a label, operated by the Swiss certification body S-Cert AG, is called GI (German abbreviation for good-indoor-climate). This label defines specific limits for over 100 typical indoor pollutants and ventilation systems, guaranteeing Green Building independent indoor air quality.
References
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7227732/
https://www.sciencedirect.com/science/article/pii/S0360132315001535 (Wei, Ramalho und Wandin)