International News
INDOOR ENVIRONMENT QUALITY
WILL BE A MAJOR OVERALL THEME IN 2021
By Messe Frankfurt
As people all around the world become far more aware of their indoor environments , the HVAC sector will play a significant role through technology , filtration , ventilation and humidity catering to the occupants ’ comfort .
The show will highlight a host of interesting and relevant issues , including ‘ Indoor Environment Quality ’. This theme covers thermal comfort and indoor air-quality hygiene .
Be it offices , administration buildings and event locations , restaurants , cinemas , theatres , department stores , shops , supermarkets , leisure facilities or industrial sites : wherever people spend longer amounts of time , the operation of ventilation and airconditioning installations ensures that constantly pleasant indoor temperatures and humidity levels , adjusted to suit requirements at the time , are maintained , and that the air quality is healthy and feels fresh . Technical regulations , standards and guidelines talk of ‘ thermal comfort ’ and the IEQ ( Indoor Environment Quality ), which involves several parameters .
Thermal comfort in interior spaces – in other words , people ’ s subjective satisfaction with the conditions in a given space – is , in large measure , dependent on the temperature in the room , the humidity level and the movement of air . The following values are considered appropriate for good IEQ and are the figures usually applied in the planning of most ventilation and air-conditioning installations in buildings and indoor communal areas :
• Room temperature : between about 20 ° C in winter and 26 ° C in summer
• Humidity level : between about 40 % in winter and 60 % in summer
• Air movement : less than about 0.2m / s in places where people congregate in order to rule out any possible danger of draughts .
Depending on the type of activity occupants are involved in ( heavy physical activity , high levels of concentration ) and how lightly or warmly the occupants are dressed , the actual ‘ target values ’ for comfort levels at a given time can vary slightly from the prescribed figures .
In addition , there is the question of ensuring desired levels of air quality . Indoor air is constantly being polluted by unpleasant odours and contaminants emanating from ceilings , walls and floors , as well as from furniture and furnishings , not to mention the pollutants released through the operation of equipment and the CO₂ that people breathe out .
The indicator and baseline level for credibly healthy and acceptable air quality , laid down in many standards and guidelines , is generally taken to be a CO₂ content of 1 000 ppm in room air – as , for instance , in DIN EN 16798 , “ Indoor environmental input parameters for design and assessment of energy performance of buildings , addressing indoor air quality , thermal environment , lighting and acoustics ”, as well as in the German workplace regulations ASR 3.6 ‘ Ventilation ’. Where CO₂ concentrations reach levels of more than 2 000 ppm , the ASR 3.6 regulations stipulate that for such , by then excessively contaminated rooms , further measures must be put in place to upgrade the ventilation system .
Like DIN EN 16798 , recent technical regulations adopt this guideline figure for CO₂ levels of 1 000 ppm . To provide good indoor air quality , they recommend that , in the planning of ventilation and air-conditioning systems , provision is made for an airflow of between around 30 to 50m ³/ h per person , representing one to two changes of room air , depending on the use to which the room is put .
This airflow is then well-filtered in the ventilation unit ( to remove dust and , where necessary , pollutant gases ), brought to the required temperature ( heated or cooled ), humidified or dehumidified and returned to the room via the ventilation system . As an equivalent volume of exhaust air is removed from the room , the continuous change of air establishes good air quality that is both hygienic and perceived as pleasant by the occupants .
Adequate air quality can also be achieved , at least intermittently , by opening the windows . But there are significant limitations to this approach and possible negative impact on comfort and air quality . Rooms overheat as a result of the ingress of warm air in summer , whilst in winter , the external air cools them down .
At the same time , the room air becomes extremely dry , which impacts on the body ’ s mucuos membranes and increases the risk of infection from bacteria and viruses . And there are other factors , too , such as the ingress of dust and street noise , as well as potentially inadequate flow of external air through the room .
None of these problems arise with a ventilation system that ducts constantly filtered , warmed or cooled air to the occupied spaces and , at the same time , removes contaminated air . It follows , therefore , that all-year-round good indoor air quality can be achieved only through the use of a mechanical ventilation unit .
Alongside temperature considerations , enduring satisfactory indoor air quality also requires adherence to the VDI 6022 standards outlining ‘ Hygiene requirements for ventilation and air-conditioning systems ’ and produced by the Association of German Engineers ( VDI ). According to these guidelines , “ ventilation and air-conditioning systems conforming to current standards should be planned , installed , operated and maintained so as to avoid negative impact on health , mental wellbeing or thermal comfort , as well as avoiding unpleasant odours .”
In order that the requirement of VDI 6022 that , “ supply air should make a positive contribution to health ” may be met , the guidelines
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