The poor standard of air quality in buildings is an increasingly serious issue that has been highlighted by the recent VW diesel emissions scandal, says Giuseppe Borgese.
22 October 2015 | By Giuseppe Borgese
Poor air quality in urban areas is held responsible for 29,000 premature deaths in the UK every year - more than obesity and alcohol combined, according to Public Health England.
Studies carried out by Kings College London link nitrogen dioxide (NO2), often caused by petrol and diesel fumes, with higher rates of mortality, lung cancer and heart failure. The World Health Organisation (WHO) has declared diesel particulates a Class 1 carcinogen.
In central London the concentrations of diesel and NO2 are about three times the level recommended by WHO. Benchmark estimates from the Harvard Six Cities survey indicate that central London suffers a 20 per cent increase in mortality rates as a result of such pollution.
The building engineering industry has been pointing out for some time that this growing outdoor air pollution epidemic also has a direct impact on people in buildings - particularly schools, hospitals and offices.
Poorly maintained ventilation systems, clogged or missing filters, dirty ductwork and ageing air conditioning systems all contribute to the problem.
We must take urgent measures to protect occupants, however, this task has been made more difficult over the past 20 years by the drive to improve energy efficiency, which has involved making buildings more airtight. Sealing up buildings puts greater pressure on ventilation systems to dilute rising levels of CO2 and replenish oxygen while simultaneously trying to stop harmful external pollutants finding their way inside.
Many airborne particles are exactly the right size for inhalation into lungs and go on to cause damage and disease. The Harvard survey showed how exposure to particles below 10 microns in size posed a serious health risk. 'Fine' particles of 2.5 microns (PM2.5) and below are particularly dangerous.
The Healthvent EU research project reported last year that almost two-thirds of the burden of disease traced to poor indoor air quality (IAQ) was from pollutants coming into buildings.
If you live on an arterial road in London you are continually exposed to two or three times more harmful particulates than WHO's warning level.
For good health and productivity the air where you live or work needs to be about 20-24°C with a relative humidity of about 40-60 per cent. The ventilation system needs to dilute CO2 levels and replace oxygen - it's a fine balance, especially when most establishments are focused on reducing energy use.
Airtight building envelopes can be a good way to keep out pollutants, but they often lead to people opening windows, which is not such a good idea.
Ensure that the ventilation system works well. Measurements have shown that a well-sealed building envelope and effective filtration of incoming supply air can reduce particle penetration by 78 per cent. There has been a growing interest in airtightness testing to help improve energy-efficiency perspective, but that process can also be used to measure IAQ.
Every planned maintenance regime should include a check on air handling unit performance as well as a ductwork hygiene inspection and remedial cleaning. The BS EN 15780 standard provides recommended inspection time periods for air systems and the revised Guide to Good Practice for ventilation system hygiene (TR/19) from the Building & Engineering Services Association (B&ES) is adopting this guidance, which can be very helpful to FMs.
BSRIA has reported a high success rate for building airtightness tests with 89 per cent of 10,000 tests meeting energy-efficiency standards set out in Part L of the Building Regulations. But it also recorded repeated problems with mechanical ventilation systems charged with ensuring these airtight buildings also benefit from adequate ventilation rates. It suggested that most problems were a result of installation faults explained by poor training and lack of experience. This is adding to IAQ issues such as condensation and damp.
Air filtration quality efficiency also has to be addressed. Standard G3 filters will not necessarily deliver the level of clean air quality required; the only available recommended solution at the moment that also provides improvements at low energy are F7 filters. In areas with high NO2 levels gas filtration should be considered. But many good filtration systems are compromised if the filters are inserted in side withdrawal mounting rails, which means the air can bypass the filter and travel around it.
Second stage air filters are designed to remove smaller particles. They must be mounted in properly engineered front withdrawal mountings to ensure they can be fully sealed to ensure air does not bypass them. Low-energy air purifiers can also be used as a room-by-room solution.
Many remedial measures are cheap. Cleaning intake grilles is straightforward and will pay back quickly because of the immediate running cost and health benefits. Servicing and upgrading ventilation fans will also ensure the system operates more effectively. But the first step is to set up a process for measuring indoor pollutants. FMs tend to be more focused on maintaining comfortable temperatures and lighting levels. They now face an IAQ problem that can affect health and productivity.
Giuseppe Borgese is chairman of the Building & Engineering Services Association (B&ES) Indoor Air Quality strategy team and general manager of Bouygues Energies & Services UK