AIR HANDLING UNITS
AHU design will be crucial to IAQ
The way air handling units (AHUs) are designed and deployed will play a big part in the UK’s increasingly urgent campaign to deal with pollution, according to Mick Humphrey, national sales manager for Daikin Applied UK.
A (NO2
ir pollution is the biggest environmental threat to human health and is responsible for as many as 36,000 deaths a year in the UK, according to Public Health England (PHE). Long-term exposure to airborne contaminants increases the risk and severity of asthma and is linked to coronary heart disease, stroke, respiratory problems and lung cancer.
Air pollution also costs our economy upwards of £20bn a year, largely due to the additional burden on the NHS. Yet, while there have been plenty of high profile efforts to measure outside air pollutants, there has been less attention paid to what this means for the indoor environment – despite the fact we spend more than 80% of our time inside buildings.
Traffic is responsible for most of the nitrogen dioxide
) pollution imposed on building occupants. This causes inflammation of the airways, reduces lung function and exacerbates asthma – with particulates also linked to heart and lung diseases, as well as certain cancers. NO2
has been blamed for more than 23,000 premature deaths every year in the UK.
The new Clean Air Act is expected to enshrine people’s right to breathe clean air as a “fundamental human right”, according to Baroness Jenny Jones, who unveiled the draft legislation in the House of Lords last summer. She said local people and communities would be able to take legal action “to defend their right to clean air” if the Clean Air (Human Rights) Bill became law.
Stakes
The first reading of the Clean Air (Human Rights) Bill was unusual because it specifically addressed indoor air quality (IAQ) for the first time – making the important health link to buildings. This considerably raises the stakes for anyone designing ventilation systems for buildings. Growing awareness of the impact of poor IAQ on health and productivity has already forced many building owners and managers to rethink their ventilation strategies, but the possibility of this being enshrined in law takes this issue to another level.
36 April 2019
Air handling units (AHUs) in particular are coming in for increased scrutiny because of their role as interfaces between potentially highly polluted outside air and the indoor environment. Modern AHUs are relatively complex systems containing a series of active components like fans, heating and cooling coils, and air filters, as well as sound attenuation technology and humidification.
on its own
AHUs are subject to the updated European Ecodesign Directive – specifically ErP 1253, which was first adopted in 2014 and came into force two years later to ensure systems meet exacting energy efficiency standards, but without loss of performance. Also, due to ever increasing energy efficiency requirements, most AHUs now incorporate heat recovery in order to reduce the amount of wasted heat. They are also subject to ISO, CEN and BSI technical standards to achieve compliance with World Health Organisation (WHO) guidelines for IAQ where people work and have public access to buildings in heavily polluted urban environments.
The design issue faced by specifiers of AHUs is that harmful particulates are getting smaller, which makes them more dangerous when inhaled as they can penetrate further into the human body. New filtration standards are focused on PM1 particulates (the smallest easily measurable), including those from diesel engines, which have been identified as a Group One carcinogen by the WHO and have also been linked in recent studies to early onset Alzheimer’s disease. This means very high standards of filtration are needed, which has a profound impact on the design of the unit and the system as a whole. F7 filters are becoming a requirement in line with the international standard EN779. This combination of heat recovery and higher specification filters means the AHU is subject to much higher pressure drops. This can mean that a larger AHU is required along with increased fan power and, therefore, larger motors that consume more energy. This flies in the face of current design trends, which have been moving towards smaller units to reduce capital cost and free up valuable lettable space in commercial buildings.
As a result, in our highly price sensitive industry there
www.acr-news.com
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56
