Passive Cooling in a Tiny House
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.
This tiny, ultra-efficient Passive House was built in just 10 days in #Australia http://t.co/glUiZVSN1o pic.twitter.com/pjYxo496ti
— The Architect’s Newspaper (@archpaper) February 10, 2015
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.
It looks like electric motorcycle influencer Surronster has landed himself in trouble south of the border, based on an arrest video posted to his social media channels.
A heavily edited video posted on his Instagram page shows the controversial rider in handcuffs being led into a police vehicle by officers in Tijuana, Mexico. The reel appears to have been filmed by a companion in the influencer’s entourage. No additional context was provided in the post, and at the time of writing, details surrounding the arrest remain unclear.
The incident comes just two days after the influencer posted another update to his social media showing that he was being denied entry into Mexico with his Sur Ron electric off-road motorcycle loaded in the bed of his truck.
In the more recent clip, the Tijuana Municipal Police appear to be questioning him and an associate before handcuffing them both. An officer is seen starting to remove the influencer’s helmet, then the clip jumps to a shot of the influencer entering the back of the police truck, edited to avoid showing his unhelmeted face. Surronster has long concealed his identity, always being filmed while wearing a full-face dirt bike helmet.
Surronster has gained a large following online by pushing the limits of electric motorcycles – especially the Sur Ron Light Bee and similar lightweight electric dirt bikes. His content often shows him performing stunts, riding in traffic without a license plate, and usually on electric dirt bikes that are not street legal for use on public roads. His 1M+ following is comprised mainly of young male viewers in their teens and twenties, with many attempting to imitate the riders’ style and stunts. He has risen to become one of the leading influencers in the electric motorbike industry, all while promoting a rebellious image and racking up millions of views on social media.
That notoriety has earned him plenty of fans, but also a long line of critics. Many in the e-bike and e-moto community have called out the influencer for encouraging illegal and unsafe behavior that risks drawing increased regulation and public backlash against electric two-wheelers, not to mention the danger to young riders who may attempt to recreate his stunts. Others defend him as a thrill-seeking entertainer similar to traditional motorsport stunt riders.
A large proportion of his videos feature illegal riding activities, but his strict control over his anonymity has meant that he has effectively operated with impunity. But getting arrested in a foreign country is a serious matter, and it remains to be seen what charges – if any – he’ll face. At the time of publishing, the Tijuana Minicipal Police have not responded to a request for comment.
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Clean energy jobs surged in 2024, growing more than three times faster than the rest of the US economy and adding nearly 100,000 new positions. That brought the total clean energy workforce to 3.56 million people, according to the 10th annual Clean Jobs America report from E2.
But growth slowed compared to 2023. Amid policy uncertainty and an overall cooling economy, clean energy jobs expanded at their slowest pace since 2020, with about 50,000 fewer new jobs than the year before.
Even so, the sector still outpaced the broader economy. Solar, wind, batteries, energy efficiency, storage, and grid jobs made up more than 7% of all new US jobs last year and 82% of new energy jobs. Clean energy also takes a bigger share of the overall workforce: it now accounts for 42% of all US energy jobs and 2.3% of the total workforce. More people work in clean energy today than as nurses, cashiers, restaurant servers, or preschool through middle school teachers.
The report lands as the clean energy industry faces major headwinds. Federal policy moves have canceled projects, revoked tax credits, and added new regulatory hurdles targeting solar, wind, EVs, and more. While not yet reflected in 2024’s numbers, those actions are already hitting jobs hard. E2 found that since January 2025, companies have canceled more than $22 billion worth of clean energy factories and projects that would have created 16,500 jobs. Other analyses warn that more than 830,000 jobs could vanish under Trump’s big bill, signed on July 4.
“This was one of the hottest and most promising job sectors in the country at the end of 2024,” said E2’s executive director Bob Keefe. “Now, clean energy job growth is at serious risk – and with it, our overall economy.”
Clean energy and EV jobs have added more than 520,000 positions over the last five years, a 17% increase. That’s far more growth than fossil fuels, ICE vehicle manufacturing, or the economy overall. In fact, over the past five years, clean energy companies have added jobs 60% faster than the rest of the US economy.
Energy efficiency remains the largest employer in the sector, with nearly 2.4 million workers after adding 91,000 jobs last year. Renewable generation jobs reached 569,000 (+9,000 in 2024), while clean vehicle jobs totaled 398,000. The clean vehicle sector shrank by 12,000 jobs in 2024 due to an industry-wide decline across all vehicle sectors, but employment is still up 52% since 2020.
Regionally, the South is leading the way. More than 1 million clean energy workers are based there, and the South added 41,000 jobs in 2024. The West and Northeast each added over 20,000 jobs, and the Midwest added 13,000. At the state level, 23 states now have at least 50,000 clean energy jobs, and in all but eight states, clean energy employment outnumbers fossil fuel jobs.
“Every year, clean energy jobs become more intertwined and critical to our overall economy,” said Michael Timberlake, E2’s director of research and publications. “These jobs are now a vital anchor of America’s energy workforce. The strength of the US job market and the future of our energy economy are now inseparable from the growth of clean energy.”
Read more: $15.5B in EV, renewable projects vanish as Senate eyes rollbacks
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Genesis is turning 10, and it’s celebrating with a few big surprises. The rising luxury brand is rolling out a slate of new hybrids and EVs, including an ultra-luxe flagship SUV and off-roader.
Genesis gears up for new EVs, hybrids, and EREVs
Hyundai’s luxury brand has quickly emerged as a dark horse in the luxury market. Genesis is celebrating its 10th anniversary with a bang.
By 2030, the brand aims to sell 350,000 vehicles annually. Genesis is launching a new lineup, including its first hybrid, a new flagship SUV, an off-roader, and several performance vehicles.
Hyundai confirmed during its CEO Investor Day on Thursday that Genesis will launch several new models soon, including new EVs, hybrids, and extended-range vehicles (EREVs).
Genesis will launch its first hybrid in 2026, followed by EREVs shortly after. At least two new SUVs are set to join the lineup, a full-size flagship model and an off-roader.
Hyundai said the new luxury SUVs will be based on the Neolun and X Gran Equator concepts. Although we have yet to learn all the details, the Neolun is expected to arrive as the GV90, an “ultra-luxe,” full-size flagship electric SUV. The X Gran Equator concept is a more rugged, luxury off-road SUV.
Genesis plans to expand the brand into up to 20 European markets while strengthening its presence in the US. Those in the US will see the first hybrid Genesis vehicles roll out, starting in 2026.
The luxury brand will also launch its first EREV, which Hyundai promises will deliver over 600 miles of range by using a battery and a gas engine that acts as a backup generator.
Genesis is entering “the realm of high-performance vehicles” with its new Magma brand. The first performance model, the GV60 Magma, will arrive later this year.
In under eight years, the Genesis brand sold a total of over 1 million vehicles. Over the next few years, it’s betting on new EVs, hybrids, advanced tech, sleek designs, and more to solidify its position in the luxury space.
Hyundai is also launching new vehicles across nearly all powertrains and segments. Check out our recap of Hyundai’s CEO Investor Day to see what’s coming.
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