It pays to maintain a healthy balance
Indoor air quality has risen up the environmental agenda as buildings have become more airtight. Alan Macklin examines the implications
Buildings are becoming more airtight as we look to reduce energy consumption so the focus has increased on the importance of indoor air quality. This is well illustrated by the HealthVent Project, a European Commission funded initiative which is developing a set of guidelines aimed at ensuring a healthy living, working and learning environment for European citizens.
The results of the project, which began in 2010, were presented in February by the HealthVent consortium at the European Parliament in Brussels. Just the headline statistics illustrate what an important issue indoor air quality has become. In Europe, people are estimated to spend at least 90 per cent of their lifetime indoors. Research in 26 European countries has shown that diseases attributable to major indoor air exposures is estimated to represent two million healthy life years annually.
Over half of these diseases are due to indoor exposure to pollutants originating outdoors, with the remainder due to pollutants from indoor sources including building materials, furnishing, equipment, consumer products and combustion, as well as the activities of the people that frequent the buildings.
The Guidelines quite rightly identify that ventilation is only part of the equation since source control (ie reducing and avoiding the dispersion of contaminants in the first place) has a vital role to play. This raises the issue of where responsibility should be placed: with the managers and regulators of the cities to ensure good outdoor air quality (which naturally ultimately impacts on indoor air quality); or rather delegated to a building level with the focus on ventilation.
In the guidelines, the recommendation is very much on the source control route, i.e. addressing the root problem of outdoor air pollution rather than seeing '...ventilation as a panacea to cope with problems of pollutant concentration indoors.'
The basic premise of the guidelines is that there should be a shift towards a health-based approach to ventilation which current EU ventilation standards do not support, offering as they do only general guidance to controlling exposure to pollutants based on recommended levels of carbon dioxide and humidity indoors.
Furthermore, the guidelines state that: 'Neither EU Standards concerning ventilation nor their related ventilation regulations, adopted by Member States at the national level, use health as the criterion for setting ventilation requirements.'
The HealthVent Project is also proving useful in moving forward the debate regarding how ventilation rates should be measured. The suggestion is that the current norm of 'air changes per hour' is '...not sufficiently clear, rigorous and meaningful'. In adopting a more health-based ventilation approach, the metrics preferred are air volume flow per unit of time per person (l/s per person) or (cu m/h per person). As with any calculation method, it is useful to have a benchmark against which indoor air quality can be measured. The project looked into identifying the lowest ventilation rate which resulted in no negative effects on health.
This was based on the air quality guidelines established by WHO (World Health Organisation), and, although the HealthVent team recognised that there are limitations and that generalisations should not be assumed too readily, ventilation rates as low as 7 l/s per person resulted in no elevated risk of asthma and allergic symptoms. The project also studied the effects of human occupation in buildings and the bio-effluents released, namely humidity and CO2, proposing a ventilation rate of 4 l/s per person as sufficient when the only source of pollution is of the human variety.
As fan manufacturers we have only a small part to play in addressing indoor air quality. This is illustrated by the varied participants of the HealthVent project team which included experts from the fields of medicine, engineering, risk assessment, indoor air sciences and ventilation, as well as patients. However, though our role may be small, it is a vitally important one since fans are at the heart of ventilation systems. As manufacturers we are already being subject to significant change with the impact of the ErP (Energy-related Products) Directive.
This has had a major impact on the way that we design our fans, putting energy efficiency to the fore of our thinking as we find ways to reduce energy consumption. We should not be afraid of change - it challenges us as designers to innovate and to rethink how we do things. With this move towards a ventilation philosophy which focuses very much on the impact of our work on the health of a building's occupants, again it is time for a re-evaluation, or at the very least, a refocusing.
Yes, our HVAC systems need to continue to ensure that the environments in which people live, work and learn are comfortable. But it is increasingly important that we recognise the term 'comfort' in its wider context. Maintaining the right temperature is part of that, ensuring that we optimise energy usage through such technology as heat recovery systems.
The Green Building Debate
However, comfort also requires that our buildings do not impact on the health of their occupants.
A report entitled 'The Green Building Debate' (LEED CERTIFICATION - Where Energy Efficiency Collides with Human Health) states: 'Greater insulation, less ventilation, and a huge increase in new chemicals and products within new buildings, collectively induce chemical exposures and threats to health never previously experienced in human history.'
We need to be mindful of these issues, recognising that in developing ever greener buildings, the environmental benefits must not be to the detriment of those for whom they are built.
// The author is technical director of Elta Group //
17 April 2013