Proving ELPO’s impact on indoor humidity.
ELPO in cooperation with Riga Stradins University and DNB bank conducted a case study in office conditions with the aim of finding out how botanical biofiltration impacts the air quality of modern buildings. The research showed that ELPO improves the air humidity in the heating season.
Dry air and its impact on human wellbeing Imagine for a moment.
It’s winter. Snow and wind are howling outside. The temperature has dropped below – 10 oC. When you touch the warm radiators, they are hot enough for you to withdraw your hand in just a moment. Perhaps the ventilation is buzzing in the background bringing in warm air into the room. Somebody sneezes. Someone else coughs. You rub your eyes, because they are aching. People get sick more often in the winter, so, perhaps, it doesn’t even cross your mind, that these symptoms are connected with the quality of the air around you.
Low air humidity is the culprit to blame for a string of unpleasant physical sensations. Under the recommended relative humidity minimum of 30%, the skin and the mucous membranes of nose and mouth dry out. So due the eyes which become even more weary if the job is done with a computer. Due to the damage to the mucous membranes, there is an increased sensitivity to pollution, which expresses itself as irritation. Therefore, people sneeze and cough more. Furthermore, mucous membranes are the ones that protect from the airborne pathogens, and if they are damaged, people get sick more often.
Low air humidity is caused by the difference between indoor and outdoor air temperatures. Cold air physically can hold a very low amount of water in comparison to warm air. Even if relative humidity outside is high in winter and doesn’t do any harm, if this air is heated, the relative humidity falls. And the bigger the difference between the temperatures inside and out, the lower it becomes. Even if the ventilation system has a means to inject water into the incoming air, it creates high energy demand, and mostly isn’t done in sufficient amounts. Furthermore, water injection is rarely found in ventilation systems at all due to the associated building and maintenance costs.
Biofilters as humidifiers
Botanical air biofilters remove air pollution with the help of plants and microorganisms, who degrade it. In order for the system to operate optimally, the substrate which is populated by these working living organisms, must be kept humid at all times. Also, for the pollution to be absorbed and for the most amount of air to be processed, the substrate has to have a large surface area and is highly air permeable, and the ventilator has to bring in more air continuously. The perfect conditions for humidification.
Though it is quite easy to calculate the amount of water that evaporates into the air by knowing the water consumption of the biofilter, this question becomes more complex when human presence, activity and ventilation is taken into account. So, it was decided that ELPO’s impact of room’s humidity in real conditions must be studied. It was possible by cooperating with the air quality specialists from Riga Stradins University and DNB bank, who gladly accepted our biofilters and the researchers in their office space.
Proving the impact on air quality
The study was done in an office building finished in 2018 on two identical floors. The test floor had a space of 700 m2 and 6 biofilters were placed in strategic locations. The ventilation system sourced the air from the roof 45 m above ground. The air exchange rate was 2,5 times per hour and there was no recuperation (heat exchange between incoming – outgoing air). It can be deducted that comparatively the ventilation is fast and the air quality high. From August till January, Aranet sensors measured air relative humidity, temperature and CO2 levels. Air pollution samples were also taken. The concentration of the total volatile organic compounds, formaldehyde and acetaldehyde and others were analysed with gas chromatography, which is a highly precise method for measuring air pollution levels.
The results of the study showed that biofilters positively impacted relative humidity. It was improved by 9% on working days and 21% on weekends when the ventilation was turned off. Even though pollution concentration did peak over the recommendation given by the World Health Organization on rare occasions (due to cleaning mostly), almost all of the time they complied to the standards or couldn’t be detected at all. It was so in both the test and the control floor. The high air quality can be explained when the CO2 measurements are taken into account. CO2 levels were relatively low for an office which were 434-750 PPM (ambient is around 250-400 PPM). In more energy efficient buildings, CO2 concentration is usually around 800 PPM.
The case study proved that ELPO botanical air biofilter can significantly improve air relative humidity. Though ELPO’s impact on air pollution must be studied more (in places with more air pollution and poorer ventilation), laboratory studies and the scientific literature shows a significant positive impact of biofiltration on air quality. ELPO is a technology that can hit birds with one stone – both clean and humidify the air, and, by doing so, improve the quality of the indoor environment and the lives of its residents.
The study “Klavina A., Berzina B., Fjodorova M., Martinsone Z. Green plant walls as indoor air quality enhancer in the recently built office building.” will be presented at the conference Healthy Buildings 2021 – Europe, which will be held on 21.-23.06.2021. The study will be added to conference proceedings