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Air pollution levels are a major cause for concern but we also need to be cautious about assuming indoor air is always better.

You may have noticed the recent campaign from The British Heart Foundation to raise awareness of the dangers of air pollution, which makes a very clear link between toxic particles in the air and an increased risk of heart attack and stroke.

The Foundation is calling on Government to change the law to help protect the health of the nation and, whilst reducing outdoor pollution will benefit everyone, we also need to be mindful of the quality of the air inside our buildings.

We all spend the overwhelming majority of our time indoors now, so ensuring we get fresh air into our internal spaces is hugely important for both comfort and Well-being.

If you live, work or go to school in a busy part of the town or city though, you are unlikely to want to open windows to let in the ‘fresh’ outside air, so how can you get rid of stale, indoor air and help yourself breathe more easily?

Cleaning up outside will only take us so far on the road to improved air quality.

Hern Yau 3 Hern Yau Ventilation expert

Beware the VOCs

The other point is that the issue isn’t just about the quality of the air we bring into our buildings. There are actually lots of hidden and potentially harmful chemicals already indoors in the form of what are known as volatile organic compounds (VOCs). These are generated from paint, furniture, printers, photocopiers and even things such as perfume and dry cleaned clothes.

In addition to this, it’s common sense to ‘clean’ our buildings which often includes using chemical sprays, and in the commercial world, this can be particularly problematic if it is cleaned afterhours when the ventilation system is shut down to save energy.

This means the chemicals can linger longer and can also be particularly harmful for the cleaners and staff working out of normal office operating hours.

Indoor air is also a mix including the outdoor air too, which can then be a double whammy for health because it can bring in the outdoor pollutants as well.

For modern internal environments therefore, the challenge is as much about getting the ‘polluted’ air out of the building as it is bringing in clean’ fresh’ air.

An ongoing problem

External air and the impact on occupants is considered at the planning stage for new buildings, with assessments made to measure air quality close to a proposed building over a certain amount of time.

Results are then used by planners to require, for example NOx and particulate matter filters, to bring air quality levels inside the building to acceptable levels.

However, the ongoing assessment of indoor air quality or IAQ is more of a challenge, partly because the built environment changes.

A building that was once near open space, may end up next to a new road – or traffic flows may increase because of changing road.

There is often little or no future analysis to check if interior air quality is still acceptable and, if the planning stage deemed it appropriate to open windows as the ventilation strategy, then there are clearly going to be issues with what’s coming into the building from outside from the changed exterior.

Building Regulations

These issues are also exacerbated by the focus on air tightness in Part L of the Building Regulations. While energy efficiency in buildings is very important, cutting down ‘leakage’ of air has put greater emphasis on the need to design ventilation systems to support good indoor air quality.

Natural ventilation is also an option. It is a solution that relies on specialist design to harness natural air currents. It offers energy saving benefits and can be a good approach for new buildings. However, for existing buildings it is a more challenging method to adopt, and the effectiveness of harnessing natural air currents can be affected if structures around a building change.

The message here is that when making decisions at the design stage of a new build or a refurbishment, it is important not to focus too much on one issue, but to take a holistic approach to considering options for ventilation.

Mechanical ventilation uses more energy to move air than relying on natural air currents. However, it offers a more predictable and reliable way to move air into (and out of) a building. Designers and their clients need to weigh up the options.

Energy saving moves

One way to mitigate against the energy use of the mechanical ventilation is to use demand control so that ventilation only works when it is required. There are a number of sensors on the market today that can not only help demand control, but they can also track IAQ and help FMs spot any unwanted drops in IAQ.

Using CO2 sensors, for example, is a good way to also measure occupancy (since humans produce CO2). A sensor in a meeting room can ensure that the mechanical ventilation reacts to a full room, but power down the fans when the room is empty. Not only does this improve the indoor environment for occupants, it also reduces energy use and saves on fan wear-and-tear.

Due to recent changes in the law on refrigerants, many building owners are taking a close look at their air conditioning systems. This could also be a good time to consider ventilation methods. It’s particularly important if the building hasn’t had air conditioning in the past.

As UK summers reach higher temperatures, businesses are looking to support staff comfort and productivity by introducing air conditioning to the building.

This can be an effective solution, but if the ventilation strategy in the past has been simply to ‘open the windows’, then adding air conditioning could actually cause issues with air quality.

Air con 101 says that you keep your windows closed when conditioning is underway or you will waste energy. However, by closing those windows you have shut off your only means of ventilation. Occupants might be cooler, but they could also be showing signs of the effects of poor IAQ such as headaches and more sickness. So it’s sensible to consider the conditioning and ventilation in tandem.

Heat recovery

Mechanical ventilation with heat recovery (MVHR) is another effective means to ensure that conditioning and ventilation work hand-in-hand in an energy efficient way.

With MVHR systems such as Lossnay, as stale air is extracted from a building, up to 80% of the temperature of the outgoing air is recovered and transferred to the incoming fresh air, keeping the building at a comfortable temperature and helping reduce overall energy costs. It works equally well in winter and summer.

For example, if the indoor air is 21°C, but the outdoor air is 27°C, then any incoming air needs to be cooled down to 21°C, which means the air conditioning needs to work harder and consume more energy.

With MVHR though, the incoming air passes over the cooler, outgoing air, to reduce the 27oC temperature to around 22.3oC. By transferring heat to the cooler outgoing air. This incoming air therefore needs less energy to bring it down to the desired temperature of 21oC, saving energy.

Even more benefits

Another benefit is that MVHR systems deliver controlled ventilation into a building through slow but constant air movement.  This has an advantage over natural ventilation which delivers uncontrolled and sometimes unreliable air flows.

A steady stream of indoor air is extracted and replaced with fresh air, rather than in ebbs and flows. By delivering a controlled air flow path throughout a building, all occupants can benefit from the improved air quality, rather than those sitting by trickle vents or the open window.

Heat recovery can also work as part of a demand-control system. For example, the Lossnay MVHR range can also be linked to CO2 sensors (or any other sensor that’s required) to operate on a demand control basis – increasing potential energy savings further.

Ventilation is key

The importance of improving our outdoor air quality should not be underestimated.

But cleaning up outside will only take us so far.

Our outdoor air could be spotless, but our buildings still need to be refreshed because we generate pollutants indoors. We can’t assume that if the external air is clean, the inside will the fine. Ventilation is key to IAQ and shouldn’t be left to chance.

All of this applies in our homes too. The National Institute of Clinical Excellence released its guidance on IAQ in homes in January 2020 (Guideline NG149). It cites poor IAQ as a source of many common illnesses and conditions. One of its important points is that heating and ventilating systems should be designed with a whole building approach “balancing indoor air quality with standards for energy use.” This is equally good advice for commercial buildings.

Hern Yau, Ventilation Product Manager at Mitsubishi Electric