AIR CONDITIONING Improving IAQ:
does energy have to be the trade-off? Jose La Loggia, president of Trane Technologies’ Commercial HVAC in EMEA explains how indoor air quality doesn’t have to come with a high environmental price-tag.
S
tudies suggest that an average person spends 90% of time indoors . Unsurprisingly, the recent COVID-19 global pandemic has shed a spotlight on
the importance of indoor air quality (IAQ), especially as schools, shopping malls, and businesses look to re-open. One of the most common recommendations provided by HVAC industry associations is to increase the building’s ventilation or fresh air rate. Essentially, this means exchanging as much outdoor air with indoor air as possible. The most simple and no-cost solution would be to open windows and allow for fresh air exchanges where possible - but this isn’t always feasible.
For warmer climates (or just most European countries in summer), ventilation and air-conditioning must go hand- in-hand. The same dilemma applies to colder climates, since introducing more fresh air in winter requires larger or additional heating systems to maintain an acceptable comfort level. Therefore, increasing ventilation rates has had HVAC designers questioning whether cooling and heating systems will need to be over-sized to compensate for the additional hot or cold air being supplied to buildings.
On the other hand, increasing ventilation rates could also lead to issues with overpressure in buildings if there is not an adequate balance between fresh air supplied and indoor air exhausted. While a slight overpressure is recommended, too much overpressure can lead to troublesome effects, such as difficulty in opening and closing doors and noisy whistling sounds due to air leakages.
This can be avoided with a proper exhaust air system in place, with the additional benefit of avoiding hot and cold spots and therefore providing a more comfortable environment. For new construction projects, this problem is addressed at the design stage. However, for renovation or retrofit projects, upgrading or implementing a mechanical exhaust air system may not be so straightforward. On top of the additional investment required, a knock-on effect may be seen on the electricity bill, with more energy being required to operate the ventilation systems. There are cases where supplying fresh air to the building is not feasible. This is why another recommendation to minimize the propagation of airborne contaminants is to clean as much as possible the recycled air. Solutions such as high efficiency particulate air (HEPA) and mechanical (F7, F9) filters have increased in awareness given the current environment. However, it is essential to note there is no single remedy or approach that works for every situation.
High efficiency mechanical filters tend to play a part in a broader set of solutions, since they are cost-effective and widely available on the European market. However, F7 and/or F9 filters have 2 to 3 times more pressure drop compared to the more commonly used G4 filters. To overcome the additional pressure drop, supply fans will need work harder to deliver the same airflow – in other words, higher energy consumption. At first glance, improving indoor air quality appears to come at the expense of oversized cooling and heating systems, and potentially more sophisticated mechanical ventilation systems. This has the potential to lead to higher energy consumption, which not only results in higher operating costs for building owners, but also goes against the EU’s climate commitment .
28 September 2020
www.acr-news.com
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