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Originally published on RMI.org.
By John Matson

As the world warms and the demand for cooling increases, many homes will require an “all of the above” approach to keep cool without further contributing to global warming. That can include high-performance cooling systems that use climate-friendly coolants and consume relatively little energy, as well as building design approaches that offset the need for mechanical cooling in the first place.

In this post, we look at some passive cooling strategies that help keep an innovative tiny house comfortable during California summers, without the use of a mechanical cooling system.

Brett Webster, a manager in RMI’s Carbon-Free Buildings program, lives in a 170-square-foot home in Sonoma County, California. Brett and his partner helped design and build the solar-powered tiny house as part of a graduate project, and they have lived in the demonstration home for about five years. The home itself was built on a 24-foot-long trailer and can be hitched up to a truck for relocation. So even though Brett and his partner have lived in their tiny home for years, they have moved twice in that time between Northern California locations (and their respective microclimates).

Strategic Shading

The walls of the tiny house are clad in reclaimed cedar slats over one-inch-thick panels of cork, which provides a layer of continuous insulation, reducing the thermal bridging of the wooden wall framing. Because the carbon sequestered in cork trees can exceed the carbon emissions of producing cork products, cork is often considered a carbon-negative material. The cedar siding is separated from the cork by an air gap, which allows the wooden slats to shade the cork and absorb solar radiation, while slowing the rate of heat transfer directly to the house. The walls of the structure are insulated with recycled denim to further limit heat gain in warm weather and heat loss in cool weather.

Pulley-mounted shade awnings, made from cedar slats to match the siding, cover the largest expanse of glass on the tiny house: a sliding-glass door at the entry to the home. Webster says that the shade structure extends far enough to block solar radiation from pouring through the glass entryway in summer, but it can let in sunlight and heat in winter, when the sun is lower in the sky.

The ability to shade the windows in summer and admit sunlight during the winter is critical to maintaining passive comfort in the house. The windows that the design team chose for the tiny house are well-insulated (low U-value) but are also designed to let the sun’s heat in (high solar heat gain coefficient), because the Bay Area is mostly a heating-dominant climate zone. During the summer, when that heat gain is not desirable, shading the windows is a necessity.

Ceiling and Roof

A layer of BioPCM phase change material in the ceiling acts like thermal mass to absorb and store heat that would otherwise warm the interior space. Adobe buildings and concrete-walled structures similarly benefit from thermal mass that prevents the interior from becoming overheated during the day. But phase change material is lightweight, making it more appropriate for applications like the ceiling of a tiny house, and it doesn’t have the carbon footprint of concrete. (Cement production alone accounts for about 8 percent of global carbon emissions.)

The phase change material, which comes embedded in sheets that can be rolled out between ceiling joists like high-tech bubble wrap, melts from solid to liquid at 77 degrees F (25°C). As it changes phases, the material absorbs a lot of thermal energy, preventing the temperature from exceeding 77 degrees until its heat-absorbing capacity has been reached, like a sponge that can’t soak up any more water.

The tiny house’s roof is designed to harness much of the sun’s energy and reject the rest. A 2.3-kilowatt solar array shades much of the tiny house’s roof and feeds into a Tesla Powerwall to store electricity for nighttime use. The “cool roof” is also covered with a light-colored acrylic roofing membrane to minimize heat gain from solar radiation.

Some Energy Required (But Not Much)

In addition to the passive cooling approaches described above, the tiny house relies on a few efficient electric devices to provide airflow and ventilation. Even though they don’t qualify as strictly “passive” technologies, ceiling fans and other efficient electric devices have long gone hand-in-hand with passive cooling approaches. The ventilation and airflow systems in the tiny house consume very little energy and allow the building to remain comfortable without a dedicated mechanical cooling system.

A high-efficiency overhead ceiling fan consumes 4–18 watts of electricity and ensures occupant comfort in warmer temperatures. “Airflow creates a cooling sensation that’s extremely effective,” Webster says. According to the US Department of Energy, using a ceiling fan can significantly offset the need for air conditioning, allowing occupants to raise the thermostat by about 4 degrees F without sacrificing comfort.

The well-insulated structure is designed to be closed off to the outside during hot days in the summer, so the windows do not provide any natural ventilation during the daytime. The tiny house therefore relies on an energy recovery ventilator to bring fresh air into the house. An energy recovery ventilator uses a heat exchanger to reduce the thermal energy of the outside air before it enters the house, thereby providing ventilation without flushing warm air into the building. In the winter, it does the reverse, using the heat of the outgoing stale air to warm the incoming fresh air.

Unplugging

The tiny house’s passive design and minimal energy requirements for ventilation make it fully capable of going off-grid, especially in the summer months when solar energy is abundant. And even if most of us aren’t ready to commit to living in a 170-square-foot house on wheels, the lessons from Webster’s tiny house and other passive homes provide a powerful reminder: Even for energy-intensive applications like cooling, with thoughtful design, you can do a lot with a little.

Image gallery courtesy of RMI.


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This new wireless e-bike charger wants to be the future of electric bikes

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This new wireless e-bike charger wants to be the future of electric bikes

Forget fumbling with cables or hunting for batteries – TILER is making electric bike charging as seamless as parking your ride. The Dutch startup recently introduced its much-anticipated TILER Compact system, a plug-and-play wireless charger engineered to transform the user experience for e-bike riders.

At the heart of the new system is a clever combo: a charging kickstand that mounts directly to almost any e‑bike, and a thin charging mat that you simply park over. Once you drop the kickstand and it lands on the mat, the bike begins charging automatically via inductive transfer – no cable required. According to TILER, a 500 Wh battery will fully charge in about 3.5 hours, delivering comparable performance to traditional wired chargers.

It’s an elegantly simple concept (albeit a bit chunky) with a convenient upside: less clutter, fewer broken cables, and no more need to bend over while feeling around for a dark little hole.

TILER claims its system works with about 75% of existing e‑bike platforms, including those from Bosch, Yamaha, Bafang, and other big bames. The kit uses a modest 150 W wireless power output, which means charging speeds remain practical while keeping the system lightweight (the tile weighs just 2 kg, and it’s also stationary).

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TILER has already deployed over 200 charging points across Western Europe, primarily serving bike-share, delivery, hospitality, and hotel fleets. A recent case study in Munich showed how a cargo-bike operator saved approximately €1,250 per month in labor costs, avoided thousands in spare batteries, and cut battery damage by 20%. The takeaway? Less maintenance, more uptime.

Now shifting to prosumer markets, TILER says the Compact system will hit pre-orders soon, with a €250 price tag (roughly US $290) for the kickstand plus tile bundle. To get in line, a €29 refundable deposit is currently required, though they say it is refundable at any point until you receive your charger. Don’t get too excited just yet though, there’s a bit of a wait. Deliveries are expected in summer 2026, and for now are covering mostly European markets.

The concept isn’t entirely new. We’ve seen the idea pop up before, including in a patent from BMW for charging electric motorcycles. And the efficacy is there. Skeptics may wonder if wireless charging is slower or less efficient, but TILER says no. Its system retains over 85% efficiency, nearly matching wired charging speeds, and even pauses at 80% to protect battery health, then resumes as needed. The tile is even IP67-rated, safe for outdoor use, and about as bulky as a thick magazine.

Electrek’s Take

I love the concept. It makes perfect sense for shared e-bikes, especially since they’re often returning to a dock anyway. As long as people can be trained to park with the kickstand on the tile, it seems like a no-brainer.

And to be honest, I even like the idea for consumers. I know it sounds like a first-world problem, but bending over to plug something in at floor height is pretty annoying, not to mention a great way to throw out your back if you’re not exactly a spring chicken anymore. Having your e-bike start charging simply by parking it in the right place is a really cool feature! I don’t know if it’s $300 cool, but it’s pretty cool!

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Tesla launches new software update with Grok, but it doesnt even interface with the car

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Tesla launches new software update with Grok, but it doesnt even interface with the car

Tesla has launched a new software update for its vehicles that includes the anticipated integration of Grok, but it doesnt even interface with the car yet.

Earlier this week, CEO Elon Musk said that Tesla would integrate Grok, the large language model developed by his private company, xAI, into its vehicles.

Today, Tesla started pushing the update to the fleet, but there’s a significant caveat.

The automaker wrote in the release notes (2025.26):

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Grok (Beta) (US, AMD)

Grok now available directly in your Tesla

Requires Premium Connectivity or a WiFi connection

Grok is currently in Beta & does not issue commands to your car – existing voice commands remain unchanged.

First off, it is only available in vehicles in the US equipped with the AMD infotainment computer, which means cars produced since mid-2021.

But more importantly, Tesla says that it doesn’t send commands to the car under the current version. Therefore, it is simply like having Grok on your phone, but on the onboard computer instead.

Tesla showed an example:

There are a few other features in the 2025.26 software update, but they are not major.

For Tesla vehicles equipped with ambient lighting strips inside the car, the light strip can now sync to music:

Accent lights now respond to music & you can also choose to match the lights to the album’s color for a more immersive effect

Toybox > Light Sync

Here’s the new setting:

The audio setting can now be saved under multiple presets to match listening preferences for different people or circumstances:

The software update also includes the capacity to zoom or adjust the playback speed of the Dashcam Viewer.

Cybertruck also gets the updated Dashcam Viewer app with a grid view for easier access and review of recordings:

Tesla also updated the charging info in its navigation system to be able to search which locations require valet service or pay-to-park access.

Upon arrival, drivers will receive a notification with access codes, parking restrictions, level or floor information, and restroom availability:

Finally, there’s a new onboarding guide directly on the center display to help people who are experiencing a Tesla vehicle for the first time.

Electrek’s Take

Tesla is really playing catch-up here. Right now, this update is essentially nothing. If you already have Grok, it’s no more different than having it on your phone or through the vehicle’s browser, since it has no capacity to interact with any function inside the vehicle.

Most other automakers are integrating LLMs inside vehicles with the capacity to interact with the vehicle. In China, this is becoming standard even in entry-level cars.

In the Xiaomi YU7, the vehicle’s AI can not only interact with the car, but it also sees what the car sees through its camera, and it can tell you about what it sees:

Tesla is clearly far behind on that front as many automakers are integrating with other LLMs like ChatGPT and in-house LLMs, like Xiaomi’s.

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Robinhood is up 160% this year, but several obstacles are ahead

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Robinhood is up 160% this year, but several obstacles are ahead

Florida AG opens probe into Robinhood. Here's the latest

Robinhood stock hit an all-time high Friday as the financial services platform continued to rip higher this year, along with bitcoin and other crypto stocks.

Robinhood, up more than 160% in 2025, hit an intraday high above $101 before pulling back and closing slightly lower.

The reversal came after a Bloomberg report that JPMorgan plans to start charging fintechs for access to customer bank data, a move that could raise costs across the industry.

For fintech firms that rely on thin margins to offer free or low-cost services to customers, even slight disruptions to their cost structure can have major ripple effects. PayPal and Affirm both ended the day nearly 6% lower following the report.

Despite its stellar year, the online broker is facing several headwinds, with a regulatory probe in Florida, pushback over new staking fees and growing friction with one of the world’s most high-profile artificial intelligence companies.

Florida Attorney General James Uthmeier opened a formal investigation into Robinhood Crypto on Thursday, alleging the platform misled users by claiming to offer the lowest-cost crypto trading.

“Robinhood has long claimed to be the best bargain, but we believe those representations were deceptive,” Uthmeier said in a statement.

The probe centers on Robinhood’s use of payment for order flow — a common practice where market makers pay to execute trades — which the AG said can result in worse pricing for customers.

Robinhood Crypto General Counsel Lucas Moskowitz told CNBC its disclosures are “best-in-class” and that it delivers the lowest average cost.

“We disclose pricing information to customers during the lifecycle of a trade that clearly outlines the spread or the fees associated with the transaction, and the revenue Robinhood receives,” added Moskowitz.

Robinhood CEO Vlad Tenev explains 'dual purpose' behind trading platform's new crypto offerings

Robinhood is also facing opposition to a new 25% cut of staking rewards for U.S. users, set to begin October 1. In Europe, the platform will take a smaller 15% cut.

Staking allows crypto holders to earn yield by locking up their tokens to help secure blockchain networks like ethereum, but platforms often take a percentage of those rewards as commission.

Robinhood’s 25% cut puts it in line with Coinbase, which charges between 25.25% and 35% depending on the token. The cut is notably higher than Gemini’s flat 15% fee.

It marks a shift for the company, which had previously steered clear of staking amid regulatory uncertainty.

Under President Joe Biden‘s administration, the Securities and Exchange Commission cracked down on U.S. platforms offering staking services, arguing they constituted unregistered securities.

With President Donald Trump in the White House, the agency has reversed course on several crypto enforcement actions, dropping cases against major players like Coinbase and Binance and signaling a more permissive stance.

Even as enforcement actions ease, Robinhood is under fresh scrutiny for its tokenized stock push, which is a growing part of its international strategy.

The company now offers blockchain-based assets in Europe that give users synthetic exposure to private firms like OpenAI and SpaceX through special purpose vehicles, or SPVs.

An SPV is a separate entity that acquires shares in a company. Users then buy tokens of the SPV and don’t have shareholder privileges or voting rights directly in the company.

OpenAI has publicly objected, warning the tokens do not represent real equity and were issued without its approval. In an interview with CNBC International, CEO Vlad Tenev acknowledged the tokens aren’t technically equity shares, but said that misses the broader point.

JPMorgan announces plans to charge for access to customer bank data

“What’s important is that retail customers have an opportunity to get exposure to this asset,” he said, pointing to the disruptive nature of AI and the historically limited access to pre-IPO companies.

“It is true that these are not technically equity,” Tenev added, noting that institutional investors often gain similar exposure through structured financial instruments.

The Bank of Lithuania — Robinhood’s lead regulator in the EU — told CNBC on Monday that it is “awaiting clarifications” following OpenAI’s statement.

“Only after receiving and evaluating this information will we be able to assess the legality and compliance of these specific instruments,” a spokesperson said, adding that information for investors must be “clear, fair, and non-misleading.”

Tenev responded that Robinhood is “happy to continue to answer questions from our regulators,” and said the company built its tokenized stock program to withstand scrutiny.

“Since this is a new thing, regulators are going to want to look at it,” he said. “And we expect to be scrutinized as a large, innovative player in this space.”

SEC Chair Paul Atkins recently called the model “an innovation” on CNBC’s Squawk Box, offering some validation as Robinhood leans further into its synthetic equity strategy — even as legal clarity remains in flux across jurisdictions.

Despite the regulatory noise, many investors remain focused on Robinhood’s upside, and particularly the political tailwinds.

The company is positioning itself as a key beneficiary of Trump’s newly signed megabill, which includes $1,000 government-seeded investment accounts for newborns. Robinhood said it’s already prototyping an app for the ‘Trump Accounts‘ initiative.

WATCH: Watch CNBC’s full interview with Robinhood CEO Vlad Tenev

Watch CNBC's full interview with Robinhood CEO Vlad Tenev

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