Lumens per watt (lumens for what?)

So many flaws in the equation:

Lumens - a simple measure of brightness based on sensitivity of ‘standard’ retina, which does not account for qualities such as glare or colour rendering.?

Watt - energy in use is a fraction of the whole life costing of a light fitting, whether you use TM65 or lifecycle assessment (LCA) to calculate this footprint -?Embodied carbon quantification of luminaires using life cycle assessment and CIBSE TM65 methodologies: A comparison case study.?

As anyone who has bought a car knows, what really counts when it comes to efficiency is where and how you drive it.?And the most energy-efficient car is the one you leave in the driveway while you cycle, walk or take the bus instead.?Embodied carbon is another important factor to consider -?Embodied carbon quantification of luminaires using life cycle assessment and CIBSE TM65 methodologies: A comparison case study.

As we move into the darker months up here in the Northern Hemisphere, there is growing evidence that we need more light during the day (and less at night) to keep the winter blues at bay -?Day and night light exposure are associated with psychiatric disorders: an objective light study in >85,000 people.

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But as regulators drive to enforce the lumens/watt metric, here are three low-tech solutions that might help us to have our eco-friendly cake and eat it.?

1. Daylight - Like leaving the car at home?

Going outside gives your body and brain a shot of mood and body clock-setting brightness and a blast of wavelengths that most artificial lights don’t provide and that most windows are engineered to block.? Growing evidence suggests that infra-red and ultra-violet wavelengths are critical for metabolism and healing, too.

Just 30 minutes outside in the morning is enough to help you get to sleep at night -?Sunlight’s effect on circadian rhythm.

90 minutes outside every day is enough to reduce a child’s risk of myopia by up to 40% -?Effect of Time Spent Outdoors at School on the Development of Myopia Among Children in China.

Exposure to infra-red wavelengths may even help to repair the retina (the light-sensing membrane) in older eyes.

If you’ve only got time for a 15 minute walk around the block, you’ll boost your ability to concentrate and reduce risk of computer vision syndrome too -?"Give me a break!" A systematic review and meta-analysis on the efficacy of micro-breaks for increasing well-being and performance.?

Your body clock is looking for contrast between bright days and dark nights. It also adds up exposure over the 24 hour cycle (your ‘photic diet’). So if you get your ‘light steps’ in the morning, you’ll cope more easily with a sneaky snack of screen time in the evening - although you might feel tired enough to nod off anyway - The human circadian system adapts to prior photic history.?

All that without burning a single watt.?

2. Windows - the next-best thing

Over 80% of employees say a window is high on their list when it comes to office perks -?Access to daylight and view in an office improves cognitive performance and satisfaction and reduces eyestrain: A controlled crossover study.

Perhaps not surprising as research suggests that the brightness and dynamic qualities of daylight, even without those extra wavelengths, will improve sleep, mood and even encourage you to be more physically active -?Access to Daylight at Home Improves Circadian Alignment, Sleep, and Mental Health in Healthy Adults: A Crossover Study,?Dynamism in the context of views out: A literature review,?Impact of Windows and Daylight Exposure on Overall Health and Sleep Quality of Office Workers: A Case-Control Pilot Study.

Light levels fall dramatically as you move away from the window, so go for the window seat if you can. For people who are more sensitive to bright light and glare, look for sheltered spaces - perhaps a bench in a snug - but aim to get a glimpse of the sky.

In spaces where windows just aren’t an option - basements and internal hospital rooms for example - artificial skylights just might help - although, unlike a window, you’ll need to plug them in -?Artificial skylight effects in a windowless office environment.?

3. Basic automation

If you remember your parents droning on about turning off the lights, you’ll know how annoying that can be.?Originally designed for security lights, a growing number of consumer products offer timed, daylight and motion-sensing features.? Research suggests we can cut energy by up to 80% with these simple tools.? I'll be trying some out in the coming months and will keep you posted.