Surveys of office workers tend to show that people generally prefer spaces with significant natural lighting and complementary levels of artificial light. Further, scientific research shows that access to more daylight can bring consistent benefits in terms of health and productivity for building occupants.
But how does natural daylight and artificial light affect energy and carbon emissions?
In this second article in our series on the potential tensions between reducing carbon emissions and health and wellbeing, we explore daylighting and artificial lighting in buildings and how they impact people and the planet.
Let there be light… but not too much?
The research suggests that people work better and sleep better when they have access to good daylighting. And practically, more daylighting means less artificial lighting needs, so this ideally can reduce carbon emissions. But does that mean that exterior walls of buildings should be 100 per cent glass?
A recent article showed what the City of Boston is doing to prevent all-glass facades in their city. Their reasoning? Glass is a poor insulator. It readily allows heat to flow in and out. A 2014 report by the Urban Green Council showed that many modern glass-façade skyscrapers have “insulation values equivalent to medieval half-timber houses”.
It’s becoming clear that ample windows may provide health and wellbeing benefits, but while they may reduce artificial lighting needs, they can drive up energy bills and carbon emissions as a result of heat gain and heat loss.
In the summer, heat gain is caused by energy from the sun heating surfaces inside the building, which then requires more air conditioning. In the winter, cold glass walls can make occupants feel cold even if the temperature in the rest of the room is comfortable. Drafts are also created as warm air hits the cold glass and falls. Thus, all-glass buildings often need heating or cooling to compensate for heat loss and gain and to maintain comfortable temperatures, driving up carbon emissions.
Interestingly, that same 2014 report noted that all-glass facades are not fully appreciated by occupants, who cover the walls with shades to reduce glare. And in any case, and as noted in the Boston Globe article, floor-to-ceiling glass doesn’t bring in that much more daylight than windows covering half the wall.
Yet we still see many all-glass skyscrapers in North American cities such as New York, Los Angeles, Boston and Toronto – because the market demands fine city-scape views.
Some building codes enforce a maximum amount of wall glass in an effort to reduce energy use. Unfortunately, this is often sidestepped in favour of other measures that improve energy efficiency.
So, does it matter? If we’re still reducing overall building energy use and providing great views and ample daylighting, should we care? We should if it makes us less resilient in the future – glass facades are difficult and costly to replace, so should be used appropriately.
Technological solutions are available though: low-glare, coated, automatically-shading, and other types of glass can reduce heat loss and gain, provide better insulation, and help provide ample natural light without significant carbon impacts. But still, caution should be taken when designing for daylight.
The rise of LEDs for greener and healthier buildings
Now we turn to artificial lighting, typically responsible for between 10 and 20 per cent of a building’s energy use. As shown above, we can’t completely eliminate artificial lighting needs with full daylighting.
The use of LEDs for artificial lighting is becoming much more common in buildings, with estimates showing they will make up 84 per cent of lighting sales by 2030, which translates to carbon savings equivalent to the energy use of 24 million homes annually. LED technologies are a great fit for health and wellbeing and energy efficiency strategies – as they appear to achieve the balance between the two. For example, blue light LEDs simulate being outdoors and make you feel less fatigued so may be preferred in certain office environments for workers, but sometimes it’s more challenging than you think.
Blake Jackson, Sustainability Design Leader at Stantec in Boston, US, explains the challenge:
“In a recent US project seeking both LEED and WELL certification, it seemed, at first glance, that the promotion of healthier interiors might have the unintended consequence of driving up energy use. However, when using tunable LEDs to achieve WELL’s circadian lighting requirement, we quickly discovered that we could meet the WELL requirements with fewer lighting banks and a much lower lighting load than we thought. Fortunately, what worked to improve health improved energy efficiency too.”
Lighting the way forward
In conclusion, we know from research that people like daylighting and that it’s good for their health, wellbeing and productivity. However, too much daylighting can lead to increased heat loss and gain, increasing energy use and carbon emissions. How do we solve this? Green building rating tools and building codes are improving and innovative construction design and technology can be used too. One key approach could be smart and efficient LED-driven lighting strategies.
If we are going to create buildings that are good for people and for the planet, and achieve the ambitious goal of 100 per cent net zero carbon buildings by 2050, then these are issues our sector needs to explore.
In the next blog in this series, we will explore the intersection of achieving good indoor air quality (IAQ), which can enhance employee productivity, and the potential implications for energy use and carbon emissions.