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.
Hyundai is the biggest winner from the US and South Korea’s new trade deal, lowering the tariff rate on imported vehicles to 15%.
Hyundai gets a break with lower US tariffs
Hyundai has committed $26 billion toward its US operations, among the biggest of any automaker. Despite this, the automaker has shelled out billions since the Trump administration slapped a 25% tariff on South Korean imports earlier this year.
The Korean auto giant is catching a break after the US and South Korea signed a new trade deal that lowered the tariff rate to 15%.
A notice posted on the Federal Register on Thursday confirmed the rate cut and other adjustments under the new deal.
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Hyundai took a 1.8 trillion won ($1.2 billion) hit from the added tariffs in the third quarter, up from just 828 billion won ($565 million) in Q3 2024.
Although it’s a lower rate, bringing it in line with Japan, which announced a similar deal in September, Hyundai will still have to pay billions in extra costs.
Hyundai IONIQ 9 models, which are built at the HMGMA EV plant in Georgia (Source: Hyundai)
“Fifteen percent is still 15%,” Randy Parker, Hyundai North America CEO, told CNBC during an interview this week.
Parker said the tariffs will be a challenge, but Hyundai is aiming for a sixth consecutive record year of US retail sales in 2026.
The Hyundai Motor Group Metaplant America (Source: Hyundai)
Hyundai Motor, including Kia and Genesis, is expected to import nearly 1 million vehicles into the US this year, or about 40% of its sales. By 2030, Hyundai aims to have more than 80% of the cars it sells in the US manufactured locally.
Hyundai IONIQ 5 at a Tesla Supercharger (Source: Hyundai)
Through November, Hyundai has sold nearly 823,000 vehicles in the US, up 8% from the same period in 2024, putting it on pace for its fifth consecutive annual retail sales record. Parker said Hyundai is “on a record pace and fully expect to go ‘5 for 5 in 2025.’”
To offset the loss of the $7,500 federal tax credit, Hyundai has been offering some of the largest discounts on electric vehicles.
The IONIQ 5, which has consistently been a top-selling EV in the US, is among the most affordable options with leases starting at just $189 a month.
Interested in a test drive? We can help you get started. Check out our links below to find Hyundai’s EVs near you.
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Elon Musk has confirmed that Tesla’s Full Self-Driving (Supervised) system now allows drivers to text and drive, though he added a caveat that it depends on the “context of surrounding traffic.”
This comes just a month after the CEO promised the feature was coming, despite the obvious legal and safety concerns surrounding it.
Does the law agree with this?
In a post on X (formerly Twitter) today, Musk responded to a question about whether the latest FSD v14.2.1 update allows for texting and driving. The CEO replied:
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“Depending on context of surrounding traffic, yes.”
This confirmation follows a statement Musk made at a shareholder meeting in early November, which we reported on at the time. Back then, Musk claimed that Tesla would “allow you to text and drive” within “a month or two” after looking at safety statistics.
It appears Tesla is moving forward with this timeline, even as FSD remains a Level 2 driver-assist system.
Currently, Tesla’s driver monitoring system uses the cabin camera to track eye movement. If a driver looks down at their phone for too long, the system issues a “pay attention” warning (often called a “nag”) and can eventually disengage the system and issue a “strike.” Five strikes result in a suspension of FSD features.
Musk’s comment suggests that Tesla is relaxing these monitoring parameters in specific scenarios, likely in stop-and-go traffic or at red lights, where the system deems it “safe” for the driver to look away.
However, this doesn’t change the legal reality. As we noted last month, texting and driving is illegal in most jurisdictions, including almost all US states. A software update from Tesla does not supersede state laws.
As we suspected at the time, instead of classifying FSD as a level 3 or 4 system, where Tesla takes responsibility for the vehicles under certain conditions and allow the driver not to pay attention, the automaker is instead simply relazing its driver monitoring rules and leaving it to the driver to take on the risk of texting and driving under its level 2 driver assistance system.
To “allow” texting and driving in a legal sense, Tesla would need to take liability for the vehicle and operate at SAE Level 3 or higher. Since FSD is still “Supervised,” the driver is 100% responsible for the vehicle. If you text and drive because Elon Musk said you could, and you crash or get pulled over, it is entirely on you.
Electrek’s Take
This is another dangerous blurring of the lines by Elon Musk.
Let’s be clear: You cannot legally text and drive just because your car’s CEO says it’s okay “depending on context.” If a police officer sees you looking at your phone, they aren’t going to care what version of FSD you are running.
What Musk really means here is that Tesla is disabling the safety feature that stops you from texting and driving in certain situations. He is removing the “nag” that detects phone use. That doesn’t make it legal, and it certainly doesn’t make it safe in a system that still requires constant supervision.
We have seen this pattern before. Tesla makes the driver monitoring looser to make the system feel more capable than it is, encouraging complacency. With FSD v14.2.1, it seems Tesla is confident enough to let you look at your phone at a red light without yelling at you. That’s a convenience feature at the cost of safety, not a step toward autonomy.
Until Tesla is willing to take liability for the drive, which they absolutely are not doing here, FSD is a Level 2 system. Eyes on the road, folks.
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Urban e-bike maker Tern just hit a major milestone in one of the toughest proving grounds on the planet: New York City. The company announced that its fleet partners have now logged more than one million miles (1.6 million km) using Tern electric cargo bikes for commercial delivery work in the city – a figure that reflects not only enormous demand for e-bike logistics, but also the durability of the hardware behind it.
According to Tern, those same cargo bikes are now completing over 13 million deliveries per year in NYC, making the bright-vested riders pulling Carla Cargo trailers an increasingly familiar sight on Manhattan streets. Many of these rigs have been in near-continuous use since their rollout in 2021, sometimes operating 16 to 20 hours a day during peak periods. In the words of Steve Boyd, Tern’s North America GM, “These bikes get hammered, and they have the scars to prove it… but they’re engineered to keep on grinding away, mile after mile.”
Delivery vans, meet your match
One of the most striking takeaways is how closely e-cargo bike efficiency now mirrors that of traditional delivery vans. Tern reports that some fleets are pulling 300-pound (136 kg) loads and hitting 360 deliveries per day, averaging more than 22 deliveries per hour.
That puts these pedal-assist workhorses squarely in van territory – but with far lower operating costs, zero tailpipe emissions, and a much smaller footprint on crowded city streets.
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NYC as the ultimate torture test
New York’s harsh winter freeze, summer heat, potholes, and relentless usage have turned the city into a stress test for every part of these bikes. Tern says that some individual units have already surpassed 30,000 miles (48,000 km) while remaining fully operational, with key components like frames and forks showing no failures. And unlike many purpose-built commercial machines that rely on proprietary parts, Tern emphasizes serviceability – most components can be maintained or replaced quickly using standard tools and off-the-shelf parts.
The Bosch motor systems powering the fleet have also held up under extreme use. According to the company, motor failures are rare, batteries continue delivering consistent performance well beyond their rated life, and Bosch’s service network has proven fast and reliable when issues do arise.
Charging at scale – safely
Operating a fleet of cargo bikes in NYC means charging hundreds of batteries every day, often simultaneously. Tern highlights that long before New York mandated UL-certified e-bikes, the company already equipped its commercial bikes exclusively with UL 2849-certified Bosch systems. After hundreds of thousands of charge cycles in dense depot environments, Tern reports zero thermal incidents across the entire fleet.
From delivery fleets to families
While these systems are clearly built to withstand commercial punishment, Tern notes that this is the same hardware sold through its consumer dealers. “Running sixteen hours a day and racking up more than ten thousand miles a year is exactly the kind of performance that shows we designed, tested, and built the bike right,” Boyd said.
That’s huge, since generally speaking, we usually see commercial bikes produced separately from consumer models, but Tern applies its same high standards to all of its bikes.
Electrek’s Take
It’s hard to find a harsher testbed than NYC delivery work. If a cargo bike can survive 20-hour days hauling 300-pound loads over Manhattan potholes, it can survive your grocery runs. What we’re really seeing here is proof that commercial e-bike logistics are scaling, are durable, and are beating vans at their own game in dense cities.
Part of that is due to the advantages of the two-wheeled model, and part of it is due to the extremely high standards to which Tern produces its bikes. I definitely feel better than ever recommending these things when someone asks me about a bike built for the long term. Sure, you pay more. But you also get more.
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