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The weakest link, making sense of the numbers – and overturning Tesla’s legacy

The weakest link?

The drive for ‘smart’ buildings automated controls risks leaving the humans who use the buildings in the dark and wasting electricity through inappropriate, inefficient or poorly-calibrated automated systems.

Time and again, post-occupancy evaluation across a range of settings suggests that occupants want more, not less control over their environment, with lighting frequently coming top of the list – Post Occupancy Evaluation of School Refurbishment Projects: Multiple Case Study in the UK.

This result is repeated in feedback from over 2,600 workers in state-funded buildings in Minnesota, who found the same central themes of inadequate control of electric lighting, automatic lighting systems that didn’t meet task-specific needs and poor integration between daylighting and electric lighting leading to excessive contrast that contributed to eye strain and migraine – The Impact of Design Interventions on Occupant Satisfaction: A Workplace Pre-and Post-Occupancy Evaluation Analysis.

Inviting us all to engage with the lighting can reduce energy use by up to 50% – Improving lighting energy efficiency through user response.

Simply switching to a manual-on option instead of the standard ‘occupancy on/vacancy off control can cut the electricity bill by up to 62%, – A preliminary study of occupants’ use of manual lighting controls in private offices: A case study.


The solution?

Ask the people who use the building what they want!

But most design decisions are made months, if not years, before the space is occupied and tenants will change over time.

So regular measurement and verification is key not only to improving environmental performance but boosting tenant satisfaction too.  

This is where smart buildings really can come into their own, with the potential to track key performance indicators that integrate the needs of people and the environment at the whole building, system and even at the equipment level as this paper explains – System-level key performance indicators for building performance evaluation.

A survey of occupants in a large American Headquarters before and after a retrofit intervention and found that, out of all the 12 indoor environmental quality categories, lighting was the dimension that received the most attention, specifically ease of control, effectiveness of automatic systems, adjustability and quality of task lighting. It also found that users considered that being able to adjust the lighting for visual comfort, and the quality of task lighting boosted their perception of how productive and healthy they were – Post-occupancy Evaluation Study of the Impact of Daylighting and Electric Lighting in the Workplace.


So what’s in the gap?

The lighting sector traditionally functions on a ‘box-shifting’ business model, where warranties and after-sales service are the first casualties of ‘value engineering’. This is compounded by the difficulty in fault finding limiting liability in a complex integrated system: where does the luminaire end and the power supply, controls and human factors begin?

This review by the International Energy Agency Energy in Buildings and Communities Programme reviews barriers to change and makes a passionate case for a paradigm shift:  Building professionals need to transition from a perception that occupants are an inconvenience – ‘sources of indoor heat gains and contaminants who are content with standardized indoor environmental conditions’ to recognising the complex and dynamic bi-directional interaction between occupants and buildings – Introducing IEA EBC annex 79: Key challenges and opportunities in the field of occupant-centric building design and operation.

Whatever the complexities, post-occupancy evaluation is likely to become the norm over the coming years, in London at least. Not simply to maintain WELL certification, but to comply with the new BSI standard 40101-Performance of occupied and operational buildings – Building performance evaluation of occupied and operational buildings (using data gathered from tests, measurements, observation and user experience). Specificationand the London Plan Policy SI 2 – The London Plan 2021 – Table of Contents that requires major developments to monitor energy usage over 5 years in use.

Perhaps it’s time to get smart about smart technology so we can take care of people and planet too.


How do you know if a research result is significant or not? 

Testing the impact of lighting is complicated because there are so many variables and knowledge is moving incredibly fast. 

When it comes to the numbers and the terminology, most of us are completely in the dark. But it’s really much easier than you think!

Different kinds of questions use different ways to describe the effects. But here are some numbers to look out for.

Probability – or how likely the result is compared to chance alone, like throwing a dice. That’s expressed as a P, or probability value. So P = 1 means the result would have happened anyway, P = <0.01 means that without this intervention, there would be less than 1% chance of this effect. P=”<0.05″ means there’s a 5% chance of this effect. That is the standard benchmark for significance.

Odds Ratio, or OR. Another way of looking at the strength of the connection between the intervention and the effect.

So if you have an odds ratio of 1, there’s no association between the exposure and the outcome.

More than one 1 tells you there’s a positive association – so an OR of 2 means the people in the experimental condition were twice as likely to experience the effect as the people who weren’t.

Less than one tells you it’s less likely to happen – an OR of 0.5 means it’s only half as likely to happen.

The last main kind is the Pearson correlation co-efficient, written as a lower-case ‘r’. That goes from -1 to +1 and shows how one variable relates to another. More than one means that as one goes up, the other goes up by that coefficient or multiplier. Less than one means that as one goes up, the other goes down.

Simple, right!


Nikola Tesla, hero or villain? 

The electric car’s namesake is a complex character, a brilliant inventor, showman and salesman who ended his life alone and almost penniless in a New York hotel room in 1943. 

Tesla was also a key player in the global decision to switch to alternating current (AC) from direct current (DC), championed by the banker JP Morgan and Thomas Edison – Tesla versus Edison: the conflict that gave us alternating current.

Tesla’s pioneering invention of AC induction motors, demonstrated at the1893 World’s fair in the celebrated ‘War of the Currents’ tipped the balance in his favour, setting the standard for electrification across the globe. More background here – War of the currents.

It’s perhaps ironic that electric cars, named after this passionate advocate of AC are tipping the economic scales back to his old rival.

This BBC podcast is well worth a listen – In Our Time.


Plants, pests and the power of darkness

As an avid amateur allotment owner, I’m becoming obsessed with plants and pests.

My little plot is tucked away in a quiet corner, next to the community orchard, so it’s reasonably protected but never gets completely dark, blighted by sky glow even in our quiet town. So I was fascinated to read about how harnessing circadian rhythms in plants can improve crop yields, reduce pesticide use and improve resilience – How understanding plant body clocks could help transform how food is grown.  Root vegetable fans may be interested to read this fascinating paper about circadian entrainment in the rhizosphere and the relationship between fungal guilds and root health – Circadian rhythms in the plant host influence rhythmicity of rhizosphere microbiota.

So while it’s tempting to focus on light, we also need to make sure the insects get a chance to do their work too. The tireless buglife campaign explains how light pollution is reducing the nocturnal pollinator visits to flowers by 62% – Light Pollution

For the urban gardener, simple solutions like closing curtains, installing a motion sensor in your outside lighting and ensuring it’s as dim as possible will help. The Dark Sky campaign has an excellent blog on how to choose the best lights here – Responsible outdoor lightingThe snails and slugs in my little patch don’t seem that bothered though!

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