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Inside & out: Can improvements in indoor air quality also achieve carbon goals?

It is well known that the quality of the air we breathe inside our workplaces can have an impact on our health, cognitive ability, job satisfaction and productivity. It’s why indoor air quality (IAQ) and ventilation are often the most talked about features when we consider health and wellbeing in buildings.

There are a host of strategies that building designers employ to improve or maintain IAQ. The most common are to use mechanical or natural ventilation to bring outdoor air into the building and to reduce the introduction of pollutants in materials during fit-outs.

But what about the energy and carbon impacts of these strategies? Does improving air quality for occupants come at an environmental price – such as higher energy use? In this third blog in our series on the intersections between reducing carbon emissions and improving health and wellbeing in buildings, we examine IAQ and ventilation.


Improving air quality & productivity

Enhanced ventilation is already prescribed in a number of green building rating tools. LEED, for example, asks for 30 per cent above ASHRAE (the American Society of Heating, Refrigerating and Air-Conditioning Engineers)-prescribed ventilation rates. Australia’s Green Star provides points for up to 100 per cent above the Australia Standard (AS) for ventilation, or where carbon dioxide levels don’t rise above 700 ppm (parts per million). There are also materials credits that promote low-VOC (volatile organic compounds) and low-pollutant paint, materials and furnishings. All of these credits are meant to improve indoor air quality.

While it is difficult to attribute specific changes in productivity to particular IAQ measures, research has consistently shown that enhanced ventilation rates above building code requirements have provided a benefit – up to 100 per cent better cognitive scores with a doubling of mechanical ventilation rates, for example. McNaughton et al. (2015) calculated that the productivity benefits were worth up to US$6500/worker/year – a significant amount.

If we’re getting this much more out of our employees, should we care about the energy impacts of boosting ventilation? Should we also be concerned about the resulting carbon emissions?


Exploring intersections with energy strategies

One key piece of research that has addressed the relationship between improving IAQ and reducing energy use was published nearly two decades ago by Mudarri (2000). In a thorough list of building strategies, he set out four categories of measures that:

  • improve energy efficiency with little impact on IAQ;
  • improve IAQ with little energy efficiency impact;
  • improve both IAQ and energy efficiency;
  • and improve energy efficiency but may compromise IAQ.

Ideally, designers and builders should focus on the second and third of these.

Interestingly, in the McNaughton et al. (2015) study, the cost of the added energy required to boost the ventilation rates that improved productivity so dramatically was only up to US$14/worker/year when energy efficient equipment was used.

So there is a tradeoff, certainly, but a small one – with improved IAQ you get substantially more out of your employees, but at slightly higher energy costs if energy efficiency strategies are employed. Mudarri also wrote in 2000 “[t]he attitudes which pit indoor environmental quality interests against interests in energy efficiency are wasteful and unnecessary” and calls for a strict protocol to develop integrated energy and IEQ strategies. That was nearly twenty years ago, so what has happened since?

More recent research suggests that there isn’t in fact any trade-off at all: Residovic (2017) examined 297 NABERS-rated buildings in Australia and found a positive correlation between NABERS Energy Efficiency (EE) and the NABERS Indoor Enviornmental Quality (IEQ) rating. As the NABERS IEQ rating of a building increased, the NABERS EE rating of the building increased as well, showing that good IEQ (including IAQ) and energy efficiency can be complementary.


The natural approach

So what about natural ventilation – is this a better solution if we want to cut carbon at the same time as improving health, wellbeing and productivity?

In some climates, natural ventilation can provide similar IAQ benefits to mechanical ventilation, at a much lower energy cost, especially when the building is designed appropriately. Research has also shown that the health benefits are potentially higher for natural ventilation compared to mechanical (Seppänen & Fisk, 2002). While some energy may still be required to condition the outdoor air, with better design and integrated thinking, natural ventilation can be part of the equation for energy efficient or net zero healthy buildings. Max Fordham’s vision of buildings that are designed “for temperate climates that need no heating energy, … that need no electrical energy for refrigeration nor … to circulate air through buildings” certainly fits in well with WorldGBC’s call for all buildings to be net zero carbon by 2050.


Energy efficiency limits trade-offs, but more research is needed

Research shows us, then, that good IAQ is beneficial to people’s health and boosts the productivity of a building’s occupants. Enhancing ventilation to improve IAQ, either naturally or mechanically, can certainly have carbon and energy impacts. However, the productivity benefits can dramatically outweigh the energy costs, or there needn’t be any trade-offs at all: energy efficient buildings can have good indoor environments.

More research is needed, though, on other factors at play. How do the trade-offs vary climate to climate; country to country; building to building?  In the journey to net zero carbon buildings that are good for people as well as the planet, this is an essential area to continue to explore.


Join the discussion

We would love to hear your views on the ideas in this article. Do you have your own experiences of tensions between the two goals of reducing carbon emissions and improving health and wellbeing, particularly when it comes to indoor air quality? How have you addressed them? We would love to feature your ideas and good case studies on this topic. Please contact Colin at

Colin Powell is Project Manager for Better Places for People, World Green Building Council

Read the first, opening piece or the second article in the series on lighting

Find our more about our Better Places for People project.