We spend around 92% of our lives indoors and with concerns about the quality of the outdoor air in our towns and cities, you may think this a good thing.
But with work being the place where we spend the vast majority of our indoor time, it’s worth noting that in many office buildings, the levels of pollutants can be 2 to 5 times higher indoors than they are outdoors.
The source may also surprise you as many of these pollutants come from the equipment and cleaning products we use, and even from the clothes we wear.
This is compounded by new building regulations which have led to a greater air tightness of these buildings, so it is no longer simply possible to open a window.
And this is where the need for better ventilation systems are becoming urgent.
We need a method of removing all the lingering pollutants to bring in fresh air from the outside
A growing problem
Growing urbanisation is exaggerating the problem, with many buildings now a mixture of retail, commerce and apartments, all built or refurbished to be much more air tight than in the past.
Whilst this is great for retaining energy and makes the buildings much more efficient, it also makes it harder to change the air without mechanical intervention.
Harmful chemicals called Volatile Organic Compounds (VOCs) are already in building materials, paints, furniture and also in cleaning products.
They are even brought in on the dry cleaned clothes we wear to work and are also produced by printers, photocopies and computers and all of these chemical pollutants linger in poorly ventilated spaces.
The physical effects
This poor air quality can be really detrimental to the performance of the building’s occupants while doing little to improve their overall wellbeing.
The physical effects can cause reduced performance, drowsiness and lack of motivation and can also be linked to long term health issues
So what is needed is a method of removing the stale air and all of the lingering pollutants to bring in fresh air from the outside.
But in these days of energy consciousness, we also need to find ways of retaining the energy we have used to heat or cool the indoor air, before we throw it out.
This is where a system called Mechanical Ventilation with Heat Recovery, or MVHR can really help.
A straightforward solution
In addition to looking at how to improve the building design, and using VOC-free materials wherever possible, mechanical ventilation systems are ideal for introducing regular fresh air to your spaces.
The best of these MVHR solutions use a special paper core that can recover up to 80% of the energy from the moisture in the outgoing air, which means you need less energy to bring the incoming air to the temperature required. This is because water holds four times more energy than air.
In simple terms, if you want the indoor to be 20 degrees centigrade and need to introduce outside air at 10 degrees centigrade, then you will literally be throwing away 10 degrees centigrade of heated air.
By using an MVHR that recovers 80% of the heat energy, the incoming air is automatically heated to 18 degrees centigrade, so your system only has to use energy to bring it up by 2 degrees, rather than 10 degrees. But the relative humidity of the incoming air will drop as it is heated up.
But if you consider the same condition above but this time take into account the moisture transfer, the incoming air will maintain the humidity and therefore the paper core will recover a total of 4.2 kW compared to a sensible only transfer of 2.5 kW of total energy. – Much more efficient!
Efficiency at its heart
The filter in these systems will also stop irritants such as pollen and other allergens from coming in with the fresh air, making them much more efficient and effective than just opening a window.
And linking these to a building management systems can help regulate the air flow throughout an entire building, with sensors throughout the buildings able to monitor and ensure the MVHR responds to varying environmental conditions, both indoors and out.
This not only ensures the maximum freshness and comfort for occupants, it also makes the building as energy efficient as possible.
We also covered this whole topic in a recent webinar which can be freely viewed by following this link.
Hern Yau is a ventilation specialist at Mitsubishi Electric