Air Pollution - What can a roof do

AIR POLLUTION – WHAT CAN A ROOF REALLY DO?

The health dangers of air pollution have taken a back seat on the sustainability agenda over recent years as much of the Government’s green focus has been on reducing levels of CO2. However, the recent heavy smog affecting much of the country, together with the prospect of EU fines for failing to meet air pollution targets, has yet again raised the issue of whether the UK should be doing more to improve its air quality. Gavin White, product manager at Marley Eternit, discusses the use of photocatalytic coatings and what impact their wider use on UK roofs could really have on air pollution.

Air pollution isn’t a problem that the majority of people in the UK worry about because the toxic mix of nitrogen dioxide and nitric oxide (collectively known as NOx) generated by road traffic exhaust fumes and industrial output is usually invisible. Apart from in busy city centres like London, it is rare to physically see air pollution, but the visible smog that engulfed the UK at the start of April has drawn much more attention to this hidden danger.

According to the World Health Organisation (WHO), air pollution is ‘the world’s largest single environmental health risk’ and links it to heart disease, respiratory problems and cancer. While the visible pollution we saw in April was much higher than usual in this country, due to a combination of Saharan dust and European industrial pollution, even at times of lower pollution, UK air quality still routinely breaches WHO recommended limits. This means that even when the air looks clean, it isn’t and according to Joe Hennon, the European Commission’s spokesman on pollution, around 30,000 people in the UK die prematurely each year from problems associated with air pollution, which is a major contributor to asthma.

The widespread media coverage of the April smog has highlighted the Government’s long term failure to reduce air pollution, with the EU launching legal proceedings against the UK for failing to reduce excessive levels of NOx pollution – mostly from traffic – after 15 years of warning. But the UK is not alone, in fact the EU is currently taking action against 17 out of 28 member states with serious air quality problems.

Air quality in the UK has actually improved in recent decades but as a spokesperson from the Department for Food, Agriculture & Rural Affairs (Defra) admitted, it remains a ‘challenge’ to meet air pollution targets near busy roads. Much of the focus to date has therefore been on the polluter itself, vehicles, by encouraging people to take fewer car journeys, to use public transport and the introduction of low emission zones in cities like London.

Reducing the amount of NOx we produce is vital, but the UK could also follow the lead of other countries such as Japan and the Netherlands by taking a two pronged approach and using photocatalytic technology on roads and buildings to effectively ‘eat’ the pollution still being produced.

Back in 2007, Marley Eternit was the first to identify the potential improvements to air quality that could be possible by applying this photocatalytic technology to roof tiles and following a period of intensive development and testing, our Ecologic tile was born. The external coating on Ecologic tiles contains titanium dioxide which speeds up the naturally occurring nitrogen cycle. The coating reacts with asthma-causing nitrogen oxides in the air to convert them to nitric acid, which is then neutralised to form calcium nitrate, a liquid fertiliser that is harmless to the environment (and, in fact, can even help to fertilise a garden). Our tests show that the coating is expected to continue absorbing pollutants for around 25 years.

Even now, seven years on, it does sound incredulous, a roof tile that can actually eat pollution, but it’s true. Using typical data on pollution levels in urban areas, coupled with our laboratory test data, we estimate that over the lifespan of an average sized roof, the amount of NOx the tiles will remove could be equivalent to that emitted by a modern car covering over 100,000 miles. Indeed, the tiles are already being used by some local authorities in the UK on their housing stock to improve air quality in the local area. We estimate that the tiles have already saved millions of car miles in pollution since they were launched.

The data from other applications of photocatalytic technology also backs this up. The technology is already used in cement on pavements in countries such as Japan, America and the Netherlands to cut pollution at the roadside. A study of busy roadways in the Netherlands found that photocatalytic concrete decreased NOx levels by 25% up to as much as 45% in ideal weather conditions.

So how much can a roof really cut air pollution by? Well, as we have seen, just one roof has an impact on surrounding air pollution levels, but imagine the impact that thousands or millions of roofs could have. Effectively each roof is taking out the pollution emissions from one car over its lifetime. If each homeowner fitted the tiles on their roof, they would absorb the equivalent NOx pollution from their car, a bit like carbon offsetting but with pollution.

In reality, vast amounts of NOx are being emitted into the atmosphere and although Ecologic tiles alone cannot eliminate this, they will make a positive difference to help reduce NOx levels. There has been so much focus at a Governmental and individual level on the benefits, both environmentally and financially, of fitting solar PV into the roof with the introduction of schemes such as the Renewable Heat Incentive. Yet, why is there no grant or incentive for homeowners to use technology on their roofs that can actually cut air pollution? If the Government truly wants to make an impact on air pollution, it needs to do more to encourage the use of photocatalytic technology and address the forgotten hazard of NOx.

For more information please click on EcoLogic to visit the product page.

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