May contain indoor air problems
- Why was the ventilation of buildings mechanized and how does living in this construction affect our health?
People spend 90% of their time indoors, children and the elderly even more. A high-quality and comfortable indoor environment is an important factor in our health and well-being (THL, 2020). It is therefore natural that there is concern about indoor air quality and that indoor air problems are being talked about more and more in the media.
Mechanical ventilation is often justified by improving ventilation efficiency, improving air quality and energy efficiency. However, mechanical ventilation requires maintenance and, if incorrectly adjusted, can cause unpredictable problems.
With mechanical ventilation, it is possible to increase the efficiency of air exchange and regulate the room air to suit different numbers of people, for example. This is especially needed in offices and public buildings. Moreover, ventilation needs can vary greatly at different times of the day. However, regulating ventilation can pose challenges to building metabolism. The resulting differences in air pressure require the rooms to be insulated from each other with heavy airtight doors. Differences in air pressure between a building and an outdoor space can cause air to pass through wall structures, instead of air valves or openings, carrying contaminants inside the structures and harmful substances released from synthetic materials such as plastic (Ikäheimo 2003 pp. 5-6). In old buildings with a solid structure (made mainly of natural materials) and gravity ventilation, no harmful substances are carried and no moisture can condense on the joints of the structural layers, as air leaks from the joints of the structures.
Air quality can be affected in mechanical ventilation for example by preheating, filtering or otherwise treating the supply air. However, mechanical ventilation also poses challenges to air quality. Too efficient ventilation and high room temperatures dry the air, especially during the heating season. Mechanically dried air has been found to cause numerous respiratory diseases and promote viral survival in room air (Wolkoff 2018, pp. 377–387). Ventilation ducts can also release harmful substances into the indoor air. Among other things, wool used in ventilation acoustics can oxidize and spread in ventilation as it ages.
The energy efficiency of mechanical ventilation is justified by the fact that it minimizes heat loss. Mechanically air-conditioned buildings can be tightly insulated, and heat loss can be minimized by heat recovery from the exhaust air. However, discussions on energy efficiency often do not take into account the own electricity consumption of mechanical ventilation, the energy used to manufacture the equipment or the built area required for ventilation (heights required for ventilation ducts, ventilation machine rooms). Ventilation-related equipment also has a shorter lifespan than a building and their replacement increases costs and energy and material consumption and requires supplementary effort. Over 150 years, a gravity ventilation system requires 15 maintenance operations, a mechanical exhaust air system 30-37 maintenance operations, and a mechanical supply and exhaust system with heat recovery 240-465 maintenance operations (Palonen p. 465, Westman 2014 p. 43-58). Thus, in 150 years, a gravity system requires only 3-6% of the maintenance required of a mechanical entry-exit system.
Complex systems are also prone to problems. Technical ventilation systems depend on properly defined presets as well as continuous service and maintenance. The 2013 report of the Parliamentary Audit Committee estimates that only 5-10% of ventilation systems have been properly maintained and cleaned (TrVM 2013, p.19). Technical systems also depend on the operation of the equipment and the availability of mains power. Regarding technical systems, the question arises: can modern buildings operate without electricity?
Gravity systems, on the other hand, utilize the forces of nature and get their energy directly from the sun. The gravity ventilation system works if supply and exhaust air exchange is enabled. The efficiency of the system has been seen as a challenge as gravity ventilation is dependent on temperature differences. During the summer, when the temperature differences are small, ventilation can be enhanced with window ventilation or various exhaust air fans. Could gravity ventilation be developed instead of the system being built entirely mechanically?
In Finland, it is currently not possible to construct a block of flats in accordance with building regulations with gravity ventilation and a solid structure, because the emphasis in the building regulations is on energy consumption and not on the overall environmental load. This creates a mismatch in which mechanical ventilation appears to be a cost-effective and energy-saving solution, even though the structures it requires are both short-lived and definitely not ecological, and lead to unhealthy indoor air.
A change in construction regulations and construction methods is therefore needed. Buildings that are healthy for people and the environment are made of breathable, natural, and recyclable materials.
Sources:
Terveyden ja hyvinvoinnin laitos (2020). Ympäristöterveys. Sisäilma. Accessed [24.9.2020]: https://thl.fi/fi/web/ymparistoterveys/sisailma
Ikäheimo, M. (2003). Helsinkiläisten asuntojen ilmanvaihto-ongelmista. Helsingin kaupungin ympäristökeskuksen julkaisuja 6/2003. Helsinki: Helsingin kaupungin ympäristökeskus.
Wolkoff, P. (2018). Indoor air humidity, air quality, and health – An overview. International Journal of Hygiene and Environmental Health, vol. 221, no. 3. p. 376–390. Accessible: DOI: 10.1016/j.ij-heh.2018.01.015
Palonen, J. Asuntoilmanvaihto [verkkoaineisto]. Helsinki: Rakennustieto. Accessed [24.9.2020]: https://www.rakennustieto.fi/Downloads/RK/RK040402.pdf
Westman, M. (2014). Poistoilman lämmön talteenotto – kannattavuus ja käyttömahdollisuudet kaukolämpökerrostaloissa. Opinnäytetyö. Arcada. Helsinki. 77 p.
TrVM. (2013). Tarkastusvaliokunnan mietintö 1/2013 vp: Rakennusten kosteus- ja homeongelmat. Helsinki: Eduskunnan tarkastusvaliokunta. 30 p. TrVM 1/2013 vp - M 5/2013 vp.
Hengitysliitto [online publication]. Accessed [24.9.2020]: https://www.hengitysliitto.fi/fi/sisailma/sisailma-asiat-sisailmaongelmat/sisailman-kosteus-ja-lampotila