What unsustainable behaviour needs to change:

Tenants usually assume that rooftop solar is only for homeowners. When people picture solar power, they imagine installing their own PV modules — something renters cannot do. This mental model forms a strong barrier: solar is not for me.

Combined with low involvement, ‘switching friction’ and the invisibility of electricity (“power just works”), many tenants stick with generic grid electricity even when cleaner, cheaper power is generated right above their home.

The Green Nudge:

By borrowing a beloved Scandinavian rooftop figure, the German energy brand Karlssonn from energy provider ALVA creates instant emotional closeness: ’something on the roof‘ feels warm and personal, not technical or exclusive.

The tagline „Your power from the roof“ frames the core promise — you don’t need to own a house to have your own power. Even the name itself does some cognitive heavy lifting: the strong consonant opening (punchy first sound), light wordplay and distinctive spelling boost salience (help it grab attention), make it more memorable and likeable.

Plain-language explainers clarify that no installation is needed. Pre-filled signup forms and building-level activation create soft defaults. Behind the scenes, a bias-aware communications toolkit addresses ‘status-quo inertia’ (sticking to what’s familiar), ‘present bias’ (favouring the short term) and ‘complexity aversion’ (avoiding what feels complicated).

The results: Early adopter buildings reached 60%+ tenant uptake, far above the 35–40% market baseline, with new buildings achieving up to 90%. The brand and explainers also significantly improved understanding of tenant-accessible rooftop solar, closing a critical awareness gap.

The Business Case: When the brand itself removes barriers, commercial performance follows naturally:

• Higher asset utilisation: More tenants choosing rooftop solar lifts self-consumption and speeds up PV payback.
• Lower acquisition costs: A memorable, behaviourally designed brand compresses the funnel and replaces costly switching pushes.
• Lower churn: Tenants feel a sense of ownership (‚my power from my roof‘), strengthening loyalty compared with generic utility offers.
• Scalable model: The brand-led nudge is transferable across buildings and cities, supporting revenue growth without eroding margins.

Karlssonn proves that when behavioural insight shapes brand strategy from the start, it becomes a core business lever.

Which other brands could use storytelling to make sustainable choices feel personal?
Share your thoughts: hello@green-nudges.com

From Nicolai Shimmels, Director of OH, BEHAVE c/o ressourcenmangel, where he brings behavioural strategy and creative brand building together to make sustainable choices intuitive for mainstream audiences. He and his team specialize in the energy sector, helping utility and energy providers design behaviour-led solutions. 

What unsustainable behaviour needs to change:

For over a century, mined diamonds have been promoted as the ultimate symbol of eternal love. From the famous slogan „a diamond is forever“ to family traditions, social norms still push couples to choose natural stones. Yet the costs are high: diamond mining is carbon-intensive, damages ecosystems, and often carries the legacy of „blood diamonds.“

Lab-grown diamonds—real diamonds produced in controlled conditions replicating natural processes—offer an identical alternative without these harms. Yet awareness remains low, and even when people know about them, cultural biases create hesitation. For many, naturally mined diamonds represent authentic romance, while lab-grown ones are stigmatized and feared as symbols of lower status.This gap in knowledge, combined with cultural attachment to mined diamonds, perpetuates an unsustainable norm.

The Green Nudge:

In a study with 551 participants, each imagined being in a jewellery shop where a customer was choosing between a mined and a lab-grown engagement ring. When shown a simple informational prompt—“Lab-grown: smaller environmental footprint, conflict-free“—perceptions shifted notably.

The lab-grown option was not only rated more positively but also seen as socially acceptable, with participants believing others would approve too. The message narrowed the perceived gap between mined and lab-grown diamonds, making the sustainable option seem equally, or even more, desirable. Both personal willingness to choose lab-grown and perceived social acceptance increased measurably.

For jewellers, this shows the power of subtle prompts: emphasising the ethical and environmental benefits of lab-grown gems in displays or advertising could accelerate acceptance. Over time, lab-grown diamonds could evolve from an alternative into the new norm.

Still, a caveat applies: this study measured attitudes and stated preferences, not actual purchases. Engagement rings are emotionally charged decisions, often influenced by social expectations. Whether these nudges translate into real-world choices remains an open question, calling for future research.

The Business Case: Lab-grown diamonds make timeless beauty accessible. Once reserved for the wealthy, synthetic diamond rings are now an affordable, sustainable option for mainstream buyers—typically 40–70% cheaper than mined stones. In 2023, lab-grown diamonds accounted for around 46% of U.S. engagement ring centre stones (Rapaport, 2024). This shift opens the market to younger and more diverse consumers who value ethics and transparency over rarity.

Which other sustainable products do you know of that are replacing  problematic “traditional” ones?
Get in touch: hello@green-nudges.com

From Kerem Güclü, Master’s student in Industrial Economics at TU Berlin, with support from the Berlin Social Science Center (WZB). His research explored how a simple social-responsibility message can shift perceptions of lab-grown engagement rings.

What unsustainable behaviour needs to change:

High meat consumption is one of the most environmentally damaging dietary habits. Livestock farming accounts for roughly 16 % of global greenhouse-gas emissions, takes up 80 % of agricultural land, and drives deforestation, biodiversity loss, water pollution, and the risk of animal-borne diseases.

Yet in efforts to reduce meat intake, one intervention has dominated: carbon labelling.

Dr Chris Macdonald, Director of the Better Protein Institute (BPI), argues that carbon labels — while well-intentioned — often underperform. They’re cognitively demanding, hard to interpret during quick decisions, and rely on complex calculations. Despite these limitations, they remain popular — something Macdonald attributes partly to “environmentalist bias”: prioritising ecological framing over consumer understanding.

The BPI takes a different approach: start by talking to the end user.

The Green Nudge:

In a UK study published in Frontiers in Sustainable Food Systems, Dr Macdonald and his team surveyed over 1,500 consumers and uncovered a key barrier: people believed plant-based meals lacked protein. He called this the “insufficiency illusion” — the mistaken belief that meat-free options fall short nutritionally.

This insight drove a large-scale experiment with over 3,000 participants. Menus were updated with a simple, factual label showing that plant-based options contained comparable protein to meat-based ones.

The results: when protein content was highlighted, meat-free meal selection more than doubled — jumping from under 25 % to over 50 %. The effect held across genders, making the meat-free option the majority choice.

This subtle label is what Macdonald calls a “nudge by proxy” — an indirect cue that shifts behaviour without highlighting the environmental problem. Rather than prescribing what to choose, it provides the specific information people feel they need.

The Business Case: For food operators, this small label delivers measurable results. Since plant-based meals are generally cheaper to produce, every additional sale contributes to higher margins. The change requires no staff training or marketing investment—just a small adjustment to menu design. And by grounding sustainability in evidence rather than ideology, it helps strengthen trust among customers and employees alike.

Do you know of any other nudges that help to promote planet-friendly food?
Feel free to get in touch: hello@green-nudges.com  

From Dr Chris Macdonald, a behavioural scientist, author, and founder. Dr Macdonald is a Fellow and Lab Director at Lucy Cavendish College, University of Cambridge; a Fellow at the Institute of Corporate Responsibility and Sustainability; a Supervisor at the University of Cambridge Institute for Sustainability Leadership; and Director of the Better Protein Institute. He was recently named one of the 40 Under 40 in Science and Innovation.

What unsustainable behaviour needs to change:

Speeding trucks on unpaved construction roads stir up large amounts of dust, posing serious health risks. Truck movement can contribute up to 50% of PM10 emissions—fine dust particles small enough to enter the lungs— on-site (Giunta et al. 2019). Yet on many sites, speed limits are ignored due to weak enforcement and low awareness.

At the Gurugram (part of the National Capital Region) pilot site—an active Indian construction zone grappling with air quality concerns—only 16% of heavy-duty vehicle drivers followed the 10 km/h speed limit. With no reminders from guards, dust control wasn’t seen as a priority.

The Green Nudge:

To reduce dust, a simple strategy was introduced: guards were trained to verbally remind incoming truck drivers about the 10 km/h speed limit and explain its role in improving air quality. Posters reinforced the message visually, and drivers were invited to voluntarily commit to following the rules.

Why did it work? People are more likely to comply when reminded by someone credible,when they actively commit to a behaviour, and when consequences are made concrete. Guards fit this role perfectly, reinforcing site rules with authority and clarity. This approach combined salient cues, social reinforcement, and personal accountability.

The results: This low-cost nudge raised compliance from 16% to 63%. As trucks slowed down, dust pollution dropped–PM10 by 11%, PM2.5 by 29%—regardless of weather conditions.

The business case: Less dust means healthier workers, fewer sick days, and stronger regulatory compliance—all achieved with minimal investment and no new infrastructure required.

Do you know of any other nudges that reduce construction site pollution and thus cut health costs?
Feel free to get in touch: hello@green-nudges.com

From the Clean Air team at the Council on Energy, Environment and Water (CEEW), Delhi: Arvind Kumar (behavioural science), Dr. Mohammed Sahbaz Ahmed (air quality modelling), Dr. Arpan Patra (urban pollution compliance), Sandeep Narang (sustainable construction), and Dr. Abhishek Kar (Senior Programme Lead). The team combines behavioural science, air quality modelling, and on-ground interventions to tackle urban air pollution—from construction dust to transportation emissions.

What unsustainable behaviour needs to change:

It’s Friday afternoon. You’re tired after a long week, rushing through the supermarket on autopilot. You have good intentions — to eat healthier, shop more sustainably — but in the moment, those values are quickly overridden by fatigue, convenience, and price cues.

Sound familiar? This everyday scenario reveals why good intentions often fall short in the grocery store. Despite growing climate awareness, most of us still grab the convenient, familiar choices. The problem isn’t that we don’t care—it’s how our brains respond under pressure.

Here’s why:

• Mental shortcuts under pressure (decision fatigue): When we’re tired and rushed, our brains default to familiar patterns
• Too much information (cognitive overload): With thousands of products competing for your attention, we can’t process what’s truly sustainable
• Bold price tags win (price salience bias): Eye-catching sale stickers trigger our deal-seeking instinct, regardless of actual value

Traditional campaigns often miss the mark on promoting more sustainable choices because they expect people to be deliberate. But most shopping is reactive– shaped by fast, unconscious judgments, not slow, rational decisions.

The Green Nudge:

In a study with a Danish supermarket, Krukow Behaviour Change tested a remarkably simple intervention:

• Yellow dot stickers were added to healthy, everyday vegetables like cabbage, potatoes, and broccoli.
• The dots mimicked „sale“ tags, using price cues to trigger the brain’s deal-seeking instinct — but without changing the price.
• These items were placed in high-traffic areas, making them easy to grab without extra effort.

The results: Shoppers who encountered the yellow dots were 46% more likely to choose the healthier option.

No discounts. No education campaign. No added friction. Just a subtle visual cue that leveraged our brain’s automatic assumption that visually prominent items offer special value (price bargain heuristic).

The intervention cost virtually nothing to implement and required no staff training or system changes. This shows how design tweaks—not big budgets or awareness campaigns—can shift real-world behavior.

The Business Case: The yellow dot acts as an evolutionary nudge that drives purchase behaviour through instinctive attention cues — raising sales without eroding margins or requiring promotion spend.

What other clever in-store nudges have you spotted that actually work?
Feel free to get in touch: hello@green-nudges.com

From Sille Krukow, a global leader in Behaviour Design with over two decades of experience helping organizations like Procter & Gamble, Electrolux, and the European Commission turn behavioral insights into measurable sustainability outcomes. She’s a frequent keynote speaker and guest lecturer whose design based methodology shows how small environmental cues can drive big shifts in decision making. 

What unsustainable behaviour needs to change:

Urban noise pollution–although often overlooked—is a silent threat. Excessive honking in congested cities like Mumbai can reach over 100 decibels, well above the WHO’s safe threshold of 85 dB.

Prolonged exposure contributes to stress, cardiovascular strain, hearing loss, and a lower quality of life—particularly for children, the elderly, and shift workers living near busy intersections.

Yet honking persists due to impatience, social norms, and the illusion of control at red lights. Traditional fines don’t scale, and awareness campaigns rarely shift deep-seated habits.

The Green Nudge:

To reshape this noisy norm, Mumbai Traffic Police, in collaboration with FCB Interface, launched a pilot campaign in late 2019 called the „Punishing Signal.“ At five busy intersections—including CSMT and Marine Drive—traffic lights were fitted with decibel meters and LED displays. If honking exceeded 85 decibels, the traffic light’s countdown timer reset, extending the red light duration.

The display delivered a cheeky but clear message: “Honk More, Wait More.”

This intervention flipped the script. Honking—usually seen as a way to assert urgency—suddenly became counterproductive. The campaign applied negative reinforcement, where the removal of an unpleasant experience (waiting) depended on a desired behaviour (staying quiet). Rather than moralising, the nudge aligned with drivers’ real-time emotions—turning impatience into a self-imposed delay.

The results

• 32 % reduction in average honking decibels one month post-pilot (Source: Ad Age)
• Widespread awareness: social media video generated 3.6 million views, 22,000+ likes, and 9,000+ retweets
• International acclaim for combining humour, salience, and enforcement—without compromising driver autonomy

By turning honking into a self-imposed penalty, Mumbai reframed impatience as an incentive to stay quiet—reducing noise pollution by nearly a third. The campaign’s traction and acclaim hint at its potential to influence public norms in other cities. 

Do you know of any clever nudges that help cut noise pollution in cities?
Feel free to get in touch: hello@green-nudges.com

From Laura Sommer PhD from the Green Nudges Consulting team. This edition explores how urban frustration was turned into a force for collective calm by Mumbai Traffic Police and FCB Interface.

What unsustainable behaviour needs to change:

The World Economic Forum’s Global Risks Report 2025 ranks misinformation as the most pressing short-term global risk. Coordinated climate mis- and disinformation is among the most damaging of forms–eroding trust, fuelling division, and delaying essential climate action.

This is not simply a failure of awareness, but a result of manipulative content designed to bypass critical thinking. Emotional language, conspiracy cues, and divisive dichotomies exploit our cognitive shortcuts—making people more likely to dismiss climate science or reject effective policies.

In a world where public consensus is vital for large-scale action, the spread of false information undermines both civic engagement and sustainable behaviour change.

The Green Nudge:

Psychological inoculation—offering a “mental vaccine” against misinformation—is proving effective in building resistance. Roozenbeek et al. (2022) tested this through “prebunking” interventions that mirror vaccine logic: exposing people to a weakened dose of misinformation, paired with a clear breakdown of the manipulative tactic behind it.

In collaboration with YouTube, short ads warned viewers about common manipulation tactics, such as emotional language and scapegoating,explained simply and reinforced with humour. The aim was to help people recognise these tricks and learn how to resist them. For example, Cambridge’s ‘Emotional Language’ prebunking video shows how alarmist words like ‘hoax’ and ‘scam’ fuel doubt about climate science– and how learning to spot these cues makes them far less persuasive.

The results: Within 24 hours, participants were significantly better at spotting misleading headlines using the tactics they had just learned. Across studies, the approach improved critical judgement and reduced willingness to share false content. These effects held up across political affiliations and demographic groups—crucial in today’s fragmented media landscape.

Implications for Communication Campaigns:
For communicators, these findings offer a practical and scalable intervention:

• Prebunking content can be integrated into social media, news platforms, or public service ads.
• Humour and storytelling improve recall, making “cognitive antibodies” stick.
• Campaigns should name the tactic, not just refute the claim (e.g. “This uses fear to manipulate you”).
• Prebunking is more effective before exposure to misinformation than reactive debunking.
• This approach supports media literacy without needing to change minds through argument—making it well-suited for polarised audiences.

Have you used similar techniques or considerations in your own communication campaigns? 
Feel free to comment or get in touch: hello@green-nudges.com

From Nanon Wollenhaupt, an applied behavioural scientist who designs evidence-based interventions for public good. Her work focuses on communication strategies and behavioural change in mental health and sustainability.

What unsustainable behaviour needs to change:

Every summer, UK music festivals generate a tidal wave of waste—an estimated 250,000 tents are left behind after just one use. Often made from non-recyclable, fossil-fuel-based materials like polyester and nylon, each tent equals the plastic content of about 200 bottles or 9,000 straws.

Despite awareness campaigns and environmental concern, this wasteful habit lingers. Why? Behavioural barriers stand in the way:

• Present bias: When tired festival-goers head home, packing up a tent feels like too much effort.
• Diffusion of responsibility: Seeing others leave their tents makes it feel acceptable to do the same.
• Perceived disposability: Cheap, easy tents marketed for single use reinforce throwaway culture.

The result? Mountains of tents destined for landfill or incineration—despite good intentions.

The Green Nudge:

Decathlon’s No Tent Left Behind campaign is a smart nudge towards circularity. Here’s how it works:

• Purchase: Buy any Decathlon tent between 9 June and 14 September 2025.
• Return: Bring it back used or unused to any Decathlon store, with proof of purchase, before 14 September.
• Reward: As a free Decathlon Member, receive a gift card for the full purchase value.
• Reuse: Returned tents are refurbished for resale through Decathlon’s Second Life programme or dismantled and recycled.

The scheme removes friction and reframes the end-of-use moment as a win-win—rewarding responsible behaviour rather than relying on guilt. It works by:

• Framing the return as a reward instead of a loss.
• Simplifying the process with clear steps and no hidden costs.
• Normalising reuse through visible reminders at festivals—look out for flags reading “I’m not leaving my tent behind. You shouldn’t either.”

By embedding circular design into the experience, Decathlon shows how businesses can lead on sustainability—making it easy to do the right thing, not harder.

Are you aware of any other nudges that help cut wasteful habits at events?
Feel free to comment or get in touch: hello@green-nudges.com

From Tessa Clarke, co-founder and CEO of Olio, the award-winning app tackling household and community waste. Tessa grew up on a farm where wasting food was unthinkable—a mindset shaped by her mother’s mantra: “Waste not, want not.” After more than 15 years in the corporate world, where waste was rife, she set out to become part of the solution. Through Olio, she’s built a global community of over 8 million users who have shared more than 100 million meals and 14 million household items—proving that systemic change starts with local action.

What unsustainable behaviour needs to change:

In densely built cities like New York, dark rooftops absorb and trap heat, intensifying the urban heat island effect. During summer, rooftop temperatures can reach up to 190°F (88°C), which is7 to10 °C higher than surrounding green spaces.

This raises indoor temperatures, strains cooling systems, and increases health risks–especially for vulnerable residents. Despite clear environmental and economic costs such as higher emissions and electricity bills, most building owners don’t take action.

Barriers include perceived complexity, upfront effort, and behavioural biases like default thinking (“my roof’s always been like this”), the invisibility of energy waste, and a tendency to underestimate long-term benefits.

The Green Nudge:

NYC °CoolRoofs makes climate action easy, social, and visible—three key ingredients for changing behaviour. Instead of relying on people to seek out solutions, the programme removes effort: building owners simply sign up online, and the city provides everything—paint, gear, and labour. This reduces friction and helps overcome the status quo bias.

The initiative is also deeply social. Volunteers, students, and community groups work together to paint roofs, creating a sense of shared purpose. This taps into social norms:we’re most likely to act when we see others doing it too.

To reinforce impact, participating buildings get a °CoolRoofs placard and are shown on public maps—offering recognition and encouraging others to follow. Before-and-after thermal images make energy savings visible, building trust and motivation.

The results:

• Since its inception in 2009, NYC °CoolRoofs has coated over 12 million square feet of rooftop surfaces across more than 600 buildings.

• The reflective coating can lower rooftop temperatures by up to 43°F (24°C) and reduce indoor temperatures by as much as 30%, leading to significant energy savings.

• For every 2,500 square feet of coated rooftop, the city’s carbon footprint shrinks by approximately one ton of CO₂ annually.

• Beyond environmental impact, the program doubles  as a workforce development initiative– providing paid training and hands-on work experience in the construction sector to job-seeking New Yorkers.

By combining smart timing, easy steps, and visible social proof, °CoolRoofs nudges people from good intentions to real action.

Do you know clever nudges that help cities stay cooler and reduce energy cost?
Feel free to comment or get in touch: hello@green-nudges.com

From the Green Nudges Consulting team—drawing on New York City’s °CoolRoofs initiative to showcase how behavioural insights can help cities stay cooler, cleaner, and more resilient.

What unsustainable behaviour needs to change:

From concrete tiles in front gardens to sealed sidewalks and patios, many cities are suffocating under impermeable surfaces. This excessive “urban sealing” blocks rainwater, overheats neighbourhoods, and erases space for biodiversity. In the Netherlands, paved private gardens alone account for over 60% of the country’s residential outdoor area, contributing significantly to local flooding and heat stress.

Still, residents often don’t realise their own driveway or back patio plays a role. It’s a classic case of ‘diffusion of responsibility’ and ‘status quo bias’—“everyone does it” and “it’s always been there.” The default is inaction.

But what if removing pavement felt like a point of pride—not a chore?

The Green Nudge:

Since 2020, the Netherlands has hosted NK Tegelwippen, the National Tile-Flipping Championship. From March to October each year, Dutch cities compete to see who can unseal the most surface area—not just tiles, but all kinds of concrete pavement.

Residents pull up slabs, bricks or tiles and register their removals online. Each city’s tally is updated live on a national leaderboard. In 2023, Arnhem led the way, removing over 460,000 tiles, while the national count surpassed 5 million since the contest began.

So why does this work so well?

• Gamification
  – Turning a sustainability task into a game adds urgency, clarity, and fun.
  – People can track progress in real-time, earn virtual recognition, and feel rewarded for each square metre unsealed.
• Social Comparison
  – Public leaderboards show which city—or neighbour—is pulling ahead, triggering friendly competition.
  – Visibility normalises the behaviour: “If others are doing it, I can too.”
• Local Pride
  – Cities and districts build identity through participation (“We’re not just greener—we’re winning!”).
  – Municipalities often highlight local champions or give small incentives (e.g. free plants or compost).

By celebrating each removed tile as part of a bigger collective win, NK Tegelwippen transforms unsealing into a shared achievement—not an isolated effort.

And it’s easy to replicate: whether in neighbourhoods, schools or housing co-ops, the magic lies in giving people permission, visibility, and momentum to rip up what’s no longer serving them—or the climate.

Do you know clever nudges that help cities stay cooler and manage water better?
Feel free to comment or get in touch: hello@green-nudges.com

From the Green Nudges Consulting team—behavioural science consultants on a mission not just to shuffle the chairs on the Titanic, but to drive real change that makes a measurable difference. We’re always inspired by bold, practical approaches that create impact at scale.