Be careful of ventilation in the home telework "air conditioner heating"!
Air conditioner heating is popular for its high safety that does not pollute the air. I think there are many people who are trying to save electricity by improving the airtightness of the room.
But there are pitfalls here. It is an increase in carbon dioxide concentration due to human breathing. Especially in eco-houses that have become more confidential in recent years, natural ventilation due to "drafts" cannot be expected, and planned ventilation is required. If neglected, in the worst case, there is a risk of harming health.
If you are staying at home for telework, why not pay attention to "carbon dioxide concentration" this winter?
In this article, I will propose the results of experiments at my home and solutions using home appliances.
■ Is carbon dioxide harmful in the first place?
Carbon dioxide is attracting attention as the leading greenhouse gas, but it is generally recognized as harmless to the human body. However, it is said that high concentrations have an impact on health, and under the Building Standards Law revised in 2003, appropriate ventilation equipment (24) for all houses so that the concentration of carbon dioxide in the living room is 1,000 ppm or less. It is obligatory to install a time ventilation system).
[Estimated carbon dioxide concentration and its effect on the human body] (Arranged independently from various indicators)
■ Experiment! What is the carbon dioxide level during telework?
Assuming actual telework, I measured the carbon dioxide concentration in my work room. The 6 tatami mats of a reinforced concrete condominium, which is relatively airtight, have windows, doors, and ventilation openings closed, and there is one adult.
The equipment used for the measurement is the Wi-Fi CO2 sensor "RS-WFCO2" of RATOC Systems, Inc., which is equipped with the highly accurate CO2 sensor "SCD40" manufactured by Sencilion. With Wi-Fi support, you can also check the carbon dioxide concentration on the smartphone app screen. In recent years, ventilation has been recommended as a measure against coronavirus, and many carbon dioxide concentration measuring machines have been commercialized as a guide, so it should be easy for anyone to obtain.
As for the experimental results, as shown in the graph, it was found that the carbon dioxide concentration reached 1,000 ppm in just one hour and continued to rise thereafter. The measurement was repeated under the same conditions for several days, but it was close to 1,500 ppm in about 2 hours. In other words, if you stay in a telework room for 2 hours and 6 tatami mats, you may feel drowsy and uncomfortable, and you may lose your concentration.
In recent years, there have been cases where a dedicated room of about 3 tatami mats has been set up for home telework, and it can be said that further attention is required in such a small space.
■ Be careful when sleeping!
It seems that you need to be careful about the concentration of carbon dioxide even at bedtime. The graph above shows the change in carbon dioxide concentration over 10 hours with one adult, with windows, doors and ventilation openings closed between 6 tatami mats. It reaches 2,000 ppm in about 5 hours, and it turns out that it is in an unfavorable state. It is necessary to be more careful when sleeping because it may last for several hours without any subjective symptoms.
By the way, when the measurement is performed with the ventilation opening opened again, the temperature rises to about 1,300ppm, but it hits the head and remains flat, as shown in the graph below. We were able to confirm a significant improvement compared to when the ventilation opening was closed, but the state of exceeding 1,000 ppm continued for a long time, and I was also worried that I felt chilly due to the intrusion of cold outside air. ..
■ What is the solution?
Even if the ventilation system (24-hour ventilation system) is operating normally, it does not mean that the telework room or bedroom is properly ventilated. It is effective to open ventilation openings and windows or open doors to ventilate, but it is still possible that ventilation is insufficient. Conversely, if ventilation is too much, the efficiency of air conditioning will decrease, and it will become cold in winter. Utility costs are also high.
First of all, I would like to recommend you to introduce a device that can measure the carbon dioxide concentration and "visualize the carbon dioxide concentration". In the case of the author's house, it was found that the ventilation port and the window were kept closed, and the door on the corridor side of the room was opened about 30 cm, and there was no extreme temperature change, and it was possible to keep about 1,000 ppm or less.
Experimenting with several ventilation patterns for each home or room should help you find the optimal solution.
■ Can't you solve it with home appliances?
In terms of air quality, "air purifiers" come to mind, but at this point there seems to be no product that can absorb carbon dioxide. As for air conditioners, the number of products equipped with a ventilation function is increasing, and a certain ventilation effect can be expected by using these. Another step forward is the combination of Daikin's air conditioner with ventilation function and "Beside" with a CO2 sensor. When the carbon dioxide concentration becomes high, the air conditioner can be automatically ventilated. In the future, these functions may become easier to use as standard functions for air conditioners.
In addition, there are products such as a ventilation air purifier (eg, Mitsubishi Electric "Rosnai VL-10SR3") that has a heat exchange function that can be retrofitted to a house.
In other words, "ventilation" is indispensable as a measure against carbon dioxide, and if you want to reduce the energy loss of air conditioning, you should consider a heat exchange type ventilation fan.
■ In the end
It can be said that the possibility of insufficient ventilation has increased due to the recent increase in airtightness of houses and heating of air conditioners. Since carbon dioxide is invisible and it is difficult to remember subjective symptoms, it would be great if this article could be used as a starting point to measure carbon dioxide concentration and lead to the practice of comfortable, energy-saving and healthy ventilation suitable for each household. I'm happy.