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Buildings are responsible for a significant part of the global energy consumption and hence stand for a considerable climate impact. To cope with the challenges related to global warming it is absolutely necessary that greenhouse gas emissions from buildings are reduced, and in that pursuit it is reasonable to think that someone questions how, and possibly even why, buildings are heated, ventilated and cooled. If all HVAC equipment were turned off, the energy consumption would decrease drastically.
A person consumes roughly one kilo of food and two to three kilos of liquid per day. Many are conscious about what, and the quality of, their foods and drinks, but is anyone questioning the quality of the 15-30 kilos of air they breathe every day?
It seems that people in general are aware of how the quality of the foods and drinks they consume impact on their health and ability to perform, but how many knows that the same goes for the quality of the air they breathe? With all respect, the air around is not as easy to pick and choose, but people in the Western world spend about 90% of their time indoors, in their homes, in school, at their workplace etc. and quality of the indoor air is of the same importance for people perform and feel good inside.
What is air?
Air consist of nearly 80% nitrogen and approximately 20% oxygen. When the human body breathes the air, it transforms the oxygen into carbon dioxide (CO2), which means that the exhaled air consists of only 17% oxygen and 4% CO2. In a room where the air is not replaced, the amount of carbon dioxide will build up and the air quality will gradually be degraded.
Research show strong correlation between the level of CO2 in the indoor air and a person’s ability to solve problems, or even manage simple tasks. It is not necessarily the CO2 per se but it is considered an important proxy for air quality. Not only is the human activity affecting the indoor air quality, also building materials, furniture, paints and things in the indoor environment emit particles or chemicals which have a negative impact on air quality.
Sick building syndrome, also known as SBS, is a building condition which causes people to not feel well inside a building. SBS can cause various illnesses to appear and it can even be the reason for chronical diseases. Time is though a relevant factor here. To prevent sick building syndrome, it is key to remove sources of harmful substances and ensure sufficient exchange of air. Ventilation.
What is ventilation?
So, it is concluded that ventilation is key for making sure indoor environments are healthy. Are opening windows or keeping openings in the building envelope for air exchange the way forward? Is the German phenomenon of "Lüften", opening windows fully to ventilate heavily, a recommendation in a world focusing on reduced energy consumption?
It is not only the “must have”-regulations in regards to mechanical ventilation that makes modern ventilation techniques beneficial. Below are four reasons to why mechanical ventilation is the only way forward when caring for the building, the planet and the people to feel good inside.
- Modern mechanical ventilation allows control over the air exchange in a building, there is nearly no risk of ventilating too much or too little. Most have probably tried to open the window in a building, but realized that it is difficult to find the perfect gap in the window shutter to ensure that the air exchange is adequate without causing draughts inside. Mechanical ventilation ensures an adequate air exchange.
- Mechanical ventilation ensure good air quality by filtering the outdoor air taken into the building. The outdoor air quality is in many places around the world poor, or even harmful, due to high levels of particulate matters. Mechanical ventilation ensures good air quality as it (in most cases) filters the outdoor air and ensures that pollen, pollution and other particles are not supplied with the fresh air.
- Mechanical ventilation brings a sound attenuation perspective to the indoor environment. Sound is a highly important indoor climate factor, sound can be pleasant and increase productivity, but noise is the complete opposite. If buildings are ventilated by the means of open windows, sounds and noise from the outdoors risk to disturb and disrupt the activity and productivity inside. Mechanical ventilation ensures a pleasurable soundscape inside.
- Mechanical ventilation needs electrical power but it ensures a balanced energy consumption thanks to efficient energy recovery. Yes, it is easy to understand that the act of opening windows to ventilate requires minimal electrical power, hence it is absolutely right that the energy consumption is close to none. However, it seems more problematic to understand that together with the stale indoor air goes the tempered indoor air. It is energy demanding to both heat and cool an indoor environment, when a window is opened, this energy goes out the window – literally. Modern mechanical ventilation is equipped with efficient solutions for energy recovery which will make sure that energy extracted from the inside of a building is brought back together with the filtered supply air.
How much energy is there to save?
The geographical location both in terms of urban/suburban and the outdoor climate obviously affects the energy savings potential. Think of an office in central London on a cold January afternoon – how much energy is saved by utilising mechanical ventilation to extract stale air but be able to remain a comfortable indoor temperature and a silent office landscape, contra opening a window? The benefits of energy recovery increase with more extreme climate conditions.
With the above in mind, literature indicates an energy save of somewhere between15-50%.
For the record, this text is not saying that opening windows is all bad, but it is highlighting the many (simultaneous) benefits of mechanical ventilation and it aims to indicate that modern mechanical ventilation is the most strategic and long term means to an energy efficient good indoor climate for people to be at their best, today and tomorrow.
