Tag Archives: building

Green walls can reduce heat lost by buildings by over 30% in temperate climates

Plants can help keep buildings warm in the winter, and cool in summer, according to new research. The trick is to plaster walls in them.

The Sustainability Hub at the University of Plymouth retrofitted with an exterior living wall facade. Image credits University of Plymouth.

Retrofitting cavity walls (double masonry walls with an air gap in between) with green or living walls goes a long way to reducing heating bills, according to new research. Such an improvement can slash the amount of heat a structure loses by over one-third (30%), the authors report.

The study was conducted at the University of Plymouth campus on its Sustainability Hub, a pre-1970 building. While the findings have practical applications for individual users, wide-scale adoption of such measures would also bring a significant and positive contribution to our efforts to combat the climate crisis.

Green for warmth

“Within England, approximately 57% of all buildings were built before 1964. While regulations have changed more recently to improve the thermal performance of new constructions, it is our existing buildings that require the most energy to heat and are a significant contributor to carbon emissions,” says Dr. Matthew Fox, a researcher in sustainable architecture and the study’s lead author.

“It is therefore essential that we begin to improve the thermal performance of these existing buildings, if the UK is to reach its target of net zero carbon emission by 2050, and help to reduce the likelihood of fuel poverty from rising energy prices.”

The study compared the insulating properties of two sections of the building’s walls with green walls providing extra insulation, using uncovered walls as a control. The green wall consisted of a flexible felt fabric sheet with a system of pockets to hold soil, in which various species of plants were planted. These included sedges, ferns, rushes, and flowering shrubs. The living wall was fitted to the exterior of the masonry wall. Due to the internal layout of the building, only one of the green-walled areas was monitored, as per the diagram below.

The performance of these two wall sections was monitored over a five-week period. By the end, the authors report, the one with the living wall facade showed a 31.4% reduction in lost heat compared to its bare counterpart.

Apart from better heat retention, the living wall also improved the thermal stability of the structure. Daytime temperatures in the two green-walled sections of the building fluctuated less than in the uninsulated ones — meaning it was easier for the buildings’ heating systems to maintain the desired temperature range.

The two monitoring locations in the building. Image credits Matthew Fox et al., (2021), Building and Environment.
A building’s U-value (thermal transmittance) showcases how much heat it transfers (loses) with its environment. Image credits Matthew Fox et al., (2021), Building and Environment.

They also discovered daytime temperatures within the newly-covered section remained more stable than the area with exposed masonry, meaning less energy was required to heat it.

Building energy use directly accounts for 17% of the greenhouse gas emissions in the UK, the authors explain. Heating alone makes up over 60% of all the energy usage in buildings, so green walls could put a significant dent in a country’s emissions if employed on a wide scale. They can also bring other benefits to the table, such as offering a way to increase biodiversity in city environments, which they sorely lack. They also provide a modest but important contribution to air filtration in cityscapes, help with our mental health, and keep temperatures in cities bearable.

On a personal note, I also find green walls to look quite cool.

This study is one of the first to look at the merits of living walls as insulation systems in temperate climates, the team adds, giving us reliable data on their effectiveness. Such data can serve both private and public actors such as homeowners, corporations, and policy-makers when deciding on what insulation systems to apply to buildings.

“With an expanding urban population, ‘green infrastructure’ is a potential nature-based solution which provides an opportunity to tackle climate change, air pollution and biodiversity loss, whilst facilitating low carbon economic growth,” adds Dr. Thomas Murphy, one of the study’s authors.

“Living walls can offer improved air quality, noise reduction and elevated health and well-being. Our research suggests living walls can also provide significant energy savings to help reduce the carbon footprint of existing buildings. Further optimizing these living wall systems, however, is now needed to help maximize the environmental benefits and reduce some of the sustainability costs.”

The paper “Living wall systems for improved thermal performance of existing buildings” has been published in the journal Building and Environment.

Researchers develop a method to 3D print buildings from any local soil

New research is making it possible to print buildings from the ground up — quite literally.

An experimental structure created with the method.
Image credits Aayushi Bajpayee.

Most construction materials today require intense processing to create. This makes them both relatively expensive, and quite damaging from an environmental point of view. But new research could make buildings dirt-cheap, by allowing their construction from actual dirt.

The building process involves a 3D printer creating the load-bearing structure out of soil (this is the part of the building that keeps it up), with the final touches to be completed from other locally-available material.

Ashes to ashes, dirt to houses

“The environmental impact of the construction industry is an issue of growing concern,” says Sarbajit Banerjee, Ph.D., the project’s principal investigator.

“Some researchers have turned to additive manufacturing, or building structures layer by layer, which is often done with a 3D printer. That advance has begun to transform this sector in terms of reducing waste, but the materials used in the process need to be sustainable as well.”

Concrete is the most widely used construction material today, but it has a high environmental footprint and requires a lot of energy and specialized installations to produce. Concrete manufacturing is responsible for around 7% of global CO2 emissions, the team notes.

Using any locally-available soils for construction would thus help ease the burden both on the environment and our savings accounts. This method has been employed for a huge part of human history, but mixing in modern technology with this ancient method can help take it to new heights.

“Our thought was to turn the clock back and find a way to adapt materials from our own backyards as a potential replacement for concrete,” says Aayushi Bajpayee, a graduate student in Banerjee’s lab at Texas A&M University.

The process uses soil as the ‘ink’ in a 3D printer (called ‘additive manufacturing’) to create the skeleton of a building. Banerjee and Bajpayee also say that the process could one day be used to create settlements on the moon or even Mars.

The team started working from soil samples collected from one of their backyards and developed a binder that would hold it together but still keep it flowy enough to go through the printer. Soils are far from uniform, and their composition can vary wildly from place to place. Because of this, the binder (or ‘additive’) is described as a chemical ‘toolkit’ designed to interact with soils of every chemistry.

The team first tested their approach by building small test structures in the shape of cubes measuring two inches on each side. Then, they tested whether the material can adequately bear weight without collapsing — for this step, they “zippered” the soil mixture into microscopic layers on the structure’s surface to prevent it from absorbing water and expanding. Using this method, the material could bear twice the load of an un-zippered one, and was deemed resilient enough. The team is still working on improving the strength of the mixture, planning to get it as close to concrete as possible.

The researchers will present their results today at the American Chemical Society (ACS) Fall 2020 Virtual Meeting & Expo.

The unseen dance between urban planning and pandemics

Our cities and pandemics go hand in hand, influencing each other in a subtle tug-and-pull, oftentimes with important and long-lasting consequences.

Among the simplest suggestions for healthier buildings: opening windows to improve air circulation and opening blinds to admit natural daylight. Credits: Lucian Alexe / Unsplash.

Diseases shape urban design

In the mid 19th century, John Snow was somewhat of an outlier in the scientific community. He wasn’t a believer in the then-dominant miasma theory which assumed that diseases such as cholera and the plague were caused by pollution or a noxious form of “bad air”. Instead, Snow believed something else was at work, so in 1854 when the cholera outbreak ravaged London, he did something no one else had thought of before: he made a map of the infection.

“[N]early all the deaths had taken place within a short distance of the Broad Street pump,” Snow wrote, identifying that water pump as the source of the cholera outbreak. With it, he discovered a pattern suggestive of a different spreading mechanism.

His theory was indeed correct. As we all know today, cholera spreads through infected water, not miasma. It took some time before Snow finally persuaded the local council to disable the public well pumps by removing their handles. It took a bit of political back-and-forth, but ultimately, Snow’s theory changed the way cities use public water pumps forever. This is just one striking example of how diseases can shape our cities, and it’s far from being an isolated one.

Urban design and public health intersect in many ways. It’s not always an exact science, as many external factors come into play in this equation (things such as culture and physical geography), but the way we design our cities does affect outbreaks.

Large cities (over 1-2 million people) tend to gain accentuated value in many societal aspects. They tend to have a better-educated population, more jobs, more entrepreneurs, and so on. But they also bring higher risks when it comes to things like violence, pollution, and epidemics. The same underlying mechanism that boosts urban innovation can also explain why certain types of crimes (and outbreaks) thrive in a larger population.

The downsides of large cities are often overlooked in comparison to the advantages they bring, but COVID-19 is forcing us to re-think how we design our cities — especially as global epidemics are becoming become more frequent. Increasingly, epidemics are becoming global — and urban — problems. This makes disease an aspect worth considering both for sprawling metropolises and up-and-coming urban areas.

More than just urbanization and densification

It’s easy to look at COVID-19 and say it was amplificated by globalization. But this doesn’t tell the whole story.

Outbreaks like this one start in and spread from the edges of cities, and into urban and suburban areas. Rapid urbanization enables the spread of infectious disease, and peripheral sites are particularly susceptible to disease vectors like mosquitoes or ticks. Increasingly, cities aren’t uniform, singular bodies — they are more like amorphous blobs, split into clusters connected in ways that are often complex. People’s income, age, habits, and culture can play a role, as do existing infrastructure and geography

They are all linked, however, by transportation. A city’s transportation is its lifeblood — and also the first route of possible disease spread. COVID-19 spread far and wide through airports, and most airports were not designed to feature quarantine areas or medical testing. This is perhaps the simplest and most consequential urban change that can be done to limit the risk of a disease spreading into the city, yet it’s often overlooked.

There is a healthy amount of chance involved in how diseases spread as well. New York is one of the most globalized cities in the world, but its outbreak happened weeks after the one in Italy and Spain, and studies have suggested that most of NYC’s coronavirus cases came from Europe itself.

Regardless of how it happens, once a disease starts to spread inside a city, things get much more complicated and site-specific.

Cities urbanize the areas around them in different ways. In the US, suburban areas are often hubs for affluent people whereas, in most of Europe, central areas are more desirable. This can influence disease spread, and it’s important to look at cities in their cultural and historic context.

Density alone also doesn’t tell the whole story.

Hong Kong. Image credits: bady QB / Unsplash.

Hong Kong has 17,311 people per square mile, and yet it managed to contain its outbreak admirably so far. It’s also a very cosmopolitan city, very close to China — a prime suspect for a severe outbreak, but Hong Kong hasn’t even come close to what New York is seeing.

Meanwhile, Washington state (much like what we have seen in Italy) is largely suburban, yet the disease has still spread with stunning speed. It’s still early to draw any crystal-clear lessons, but the level of urbanization doesn’t necessarily seem to correlate with how heavily hit an area is. There are likely other, more subtle aspects at play, which city planners will need to analyze and adapt to, just like they did after John Snow’s findings.

Rich-poor segregation also doesn’t really help cluster down the outbreak. In several US communities, the disease was brought in by inhabitants of affluent suburbs, but then disproportionately spread to some of the poorest neighborhoods. Quite likely, some affluent areas are spared because their inhabitants can afford to enter quarantine or work from home, whereas this might not be the case in other neighborhoods.

Digital infrastructure

Imagine if this pandemic would have happened 10 years ago. The mere thought that we would have to do this without internet deliveries is horrifying. Then, there’s all the digitized information that both we as citizens and decision-makers have available at our fingertips. There’s never a good time for a pandemic, but at least in terms of digital infrastructure, we’re way better prepared than we were a few years ago.

Digital infrastructure is becoming an increasingly important part of a city’s infrastructure, but we need to find ways to use it properly.

The next challenge is to figure out what data is useful, how to get it, and how to make decisions off of it. A good example in the current pandemic is Johns Hopkins’s CSSE aggregator of information. This dataset and visualization, which we have also used, was extremely useful in understanding the scale and overall evolution of the disease at the global level. As the outbreak progressed, several other datasets emerged, on international, national, and even local levels.

Having access to this unprecedented level of data is a game-changer. Even for cities lacking a solid digital infrastructure, having access to open-source data enables decision-makers to plan with unprecedented quality of information. Meanwhile, countries that have invested in building this digital infrastructure up are reaping the rewards. In Germany, for instance, you can watch a real-time map of hospital bed capacity, showing which areas are at full capacity and which can still take extra patients — an initiative which can be carried out at low costs, but which can carry huge rewards.

Much like they organize streets and buildings, city planners will need to look at what digital infrastructure is required in a city, and how it can be organized and used both in normal times and in times of crisis. The amorphous shape of cities will also carry on to the online infrastructure.

Looking into the next few years, as the world will start to shake off the COVID-19 crisis, we will enter another wave of megaurbanization. Urban regions would do well to develop efficient and innovative methods of confronting emerging infectious disease without relying on drastic top-down state measures that can be disruptive and often counter-productive.

Over the course of this pandemic, the US has demonstrated just how important it is for cities to be able to fend for themselves, and how devastating it is when they don’t.

In general, urbanization plans should account for fighting racism and intercultural conflict. Epidemic planning also falls into this category, and it’s more important than ever for cities to also consider this.

Cities are hotspots of innovation and solution-finding, but they can also be hotspots of disease spread. From cities, we will find both our solutions and our biggest problems. COVID-19 isn’t the last global outbreak we will have to face. Hopefully, the world’s cities will rise up to the challenge.

Burh Becc.

Incredible farm in Michigan becomes the world’s second ‘Living Building’

A beautiful, 15-acre farmhouse in Ann Arbor, Michigan has been officially recognized as the world’s second Living Building by the International Living Future Institute (ILFI).

Burh Becc.

Burh Becc at Beacon Springs.
Image via ILFI.

The owners, Tom and Marti Burbeck, worked with a team of over 20 designers, engineers, architects, and sustainability experts over the last five years to transform their home from a consumer to a net producer.

The design of Burh Becc, as the building has been christened, was inspired by traditional Tuscan farmsteads, and sports a 2,200 sq ft (204.4 sq m) living space, alongside a 2,400 sq ft barn and workshop. The arable land on the property had been depleted after years of commodity farming and was revamped following the criteria set out by Living Building — using permaculture farming methods and an integrated system of agriculture, horticulture, and ecology.

The approach should create a system that will keep regenerating the soil for decades, maybe even centuries to come. The Burbecks use the farmland to grow their own food and provide produce for the local community.

A building’s life

So, what is a Living Building? Well, according to the ILFI’s website,

Living Buildings are:

• Regenerative buildings that connect occupants to light, air, food, nature, and community.

• Self-sufficient and remain within the resource limits of their site.

• Create a positive impact on the human and natural systems that interact with them.

Burth Becc is a net-zero energy design. It’s equipped with a 16.9-kilowatt solar array which can provide for all the farm’s energy needs and still have some extra to feed back into the grid. Heating is handled by a passive solar system, supported by a tight thermal envelope and a cooling tower, both of which help limit energy expenditure on heating and cooling. During the winter, the home is kept toasty warm through floor heating, supplied by a closed-loop geothermal system.

The Burbecks can also call on a rainwater and snow harvesting system, which makes their home, for all intents and purposes, water net-positive. A rainwater collector feeds non-potable water to huge, 7,500-gallon underground cisterns. Potable water is drawn from an on-site well (necessary to comply with local building codes), but the home is equipped with a potable rainwater filtration system that can be switched on at a moment’s notice.

After more than three and a half years spent on designing their home, 18 months to construct it, and a year of performance auditing, Burh Becc at Beacon Springs Farm became the second building to ever be awarded the Living Building Challenge certification in December 2017. Additionally, the home has been awarded a Platinum LEED Certification.

The Burbecks say the project made sense, considering their lifestyle.

“As we looked at the criteria for LBC certification we thought, why not go for it,” says Marti Burbeck.

“If our goals include helping to change peoples’ relationship with the environment and to change building philosophies, we should start with our own project, and then become advocates.”

The couple now plans to host educational workshops and house tours for members of the community, building industry, officials, and pretty much anyone who’s interested in sustainable living.

Superdense wood.

Strong as steel and lightweight? Must be superdense wood

American researchers are giving the term hardwood a whole new meaning. They have developed a relatively simple, boil-and-crush technique to make “superdense” wood — a strong but lightweight material which could be used to build everything from bridges to cars.

Superdense wood.

The wood-compacting process crushes gaps between cell walls in natural wood seen in the scanning electron microscopy image on the left), making densified wood (right) as strong as steel.
Image credits J. Song et al., Nature, 2018.

People have built and crafted with wood since times immemorial, and for good reason: it’s a plentiful, cheap, readily available building material (in most parts of the world), it’s got a good blend of strength and flexibility, and it’s relatively easy to work with. It also, to me at least, looks quite nice. Our relationship with wood as a building material, however, started to taper out with the industrial revolution, and today, it’s more of an occasional fling on the side than anything serious.

Old log, new tricks

Which is actually quite sad, as although wood lagged behind in the “strength” department, all its other qualities are still there. In a bid to put the spark back in this old flame, a team of US researchers has developed superdense wood — a highly-compacted wood that’s about as strong as steel, but much more lightweight.

The enviable physical properties of this material can be traced back to its production. It is constructed by boiling regular blocks of wood in a water-based solution of sodium hydroxide (lye) and sodium sulfite. These chemicals remove part of the lignin and hemicellulose in the wood (two organic compounds that give wood its structure and rigidity), making it more malleable.

This limbered-up lumber is then pressed at 5 megapascals (50 times the atmospheric pressure at sea-level) between two metal plates heated to 100° Celsius (212° F). The process squishes all the gaps between cells in the wood, shrinking the block to about 20% its initial thickness and increasing density three-fold.

With great squish comes great power, however: mechanical testing revealed that ultradense wood produced in this manner can withstand being stretched or pulled 11.5 times harder than the original without breaking. This would make it comparable to steel in strength, although it’s also more lightweight. The team also tested typical and superdense wood planks against stainless steel pellets fired from an airgun at 30 meters (98.5 feet) per second. The pellets went clean through the natural wood, but got lodged in the stack of densified wood of the same thickness, as you can see below:

Another advantage of the process, notes co-author Teng Li, a mechanical engineer at the University of Maryland in College Park, is that the chemicals used to scrub lignin and hemicellulose from the wood won’t pose any significant pollution concerns. In light of that fact, and of wood’s comparatively low environmental impact and sustainability, superdense wood could become an eco-friendly alternative to steel or other metallic alloys for construction works. Alternatively, it could be used in the manufacturing of more light-weight, more fuel-efficient vehicles, he adds.

As a final morsel for thought: wood is, ultimately, a form of carbon storage — plants, after all, scrub carbon from the atmosphere to grow. Viewed in this light, using superdense wood as a building material on a wide scale could help us hit two birds with one stone (if it’s harvested sustainably, of course). On one hand, it would help reduce carbon emissions from metal and non-metal mining and refining. On the other, it would capture some of the CO2 that’s already floating around. We can even make the window panes out of wood!

With the climate woes we’re facing, and those waiting for us in the future, we’ve got very few such stones to throw — and we need to get as many birds as we can.

The paper “Processing bulk natural wood into a high-performance structural material” has been published in the journal Nature.

The Mars brick.

Turns out you can make harder-than-concrete bricks on Mars simply by compressing soil

Mars colonizers might use the planet itself to make their homes — a new technique has been developed which can turn Mars’ reddish soil into bricks without the need for ovens or any extra ingredients. All you need to do is press hard enough on it.

The Mars brick.

Made from compacted Martian soil, without the need for additional ingredients or baking, this simple brick could one day house our first colonists on the red planet.
Image credits Jacobs School of Engineering / UC San Diego.

We’ll need to design a new range of materials if we’re to colonize space. Not only because they need to resist the vicissitudes of whatever planet or body we’re aiming to settle on, but also to save on cash — shuttling things through space is really expensive. Mars is the likely candidate for our first colony.

The idea of using its soil to build the first homes up there isn’t new. But previous technologies were reminiscent of traditional brick-making back on Earth, requiring brick kilns (nuclear-powered, of course), or involved mixing the material with chemical mixes to turn in-situ organic components into binding polymers.

It seems that we don’t have to do any of those things — making bricks on Mars is as easy as compacting soil. The surprising technology was developed by a team of engineers at the University of California San Diego, who initially started work with Mars soil simulant to try and reduce the amount of polymers required in brick-making.

To their surprise, they found out that only two steps are needed to turn the red dirt into a resilient building material. First, you have to place the soil in a flexible container (the team used a rubber tube). Then, you press it really hard — for a small sample, roughly the same pressure generated by a 10-lb hammer droped from a height of one meter is enough, said Yu Qiao, a professor of structural engineering at UC San Diego and the study’s lead author.

“The people who will go to Mars will be incredibly brave. They will be pioneers. And I would be honored to be their brick maker,” Qiao, added.

Their process results in small, round soil pallets that are about one inch tall that can later be cut into individual bricks. It likely all comes down to the iron oxide in the soil, the team says. Qiao and his team studied the simulant’s structure with various methods and found that the iron oxide particles coat the larger basalt bits in the martian soil. This is the same substance that lends Mars its shade of red and forms flat particles with clean facets which readily binding together under pressure, basically performing the same task as any added polymers would.

When testing the bricks’ strength, the team was surprised to find that they were stronger and more resilient than steel-reinforced concrete even without any kind of rebar. Which is a lot. Quao’s team says their method may be compatible to additive manufacturing, meaning astronauts wanting to build a structure would simply have to lay down a layer of dirt, compact it, lay another layer and so on until they’re done.

Next on the list, they say, is to tailor the production method to create bigger bricks.

Parasitic wooden cubes level up 1970s Parisian building with more space, more energy efficiency

“Parasite” wooden cubes may help extend the livelihood of old buildings by increasing available space and improving energy efficiency. The cubes were designed by architect Stéphane Malka as part of the Plug-in City 75 project and will be attached to the facade of a 1970s-era Parisian building slashing its annual energy consumption by roughly 75 percent.

Faced with gloomy, cramped apartments and poor energy efficiency of a by-gone era of building, the co-owners of a Parisian building in the city’s 16th arrondissement asked Malka to spruce up their property. It’s just one of many buildings facing these issues in Paris, but since the city’s building laws are quite restrictive and do not allow for the building to be raised to make way for better, more efficient space, he couldn’t just tear it down and replace it.

So he decided to level it up. And what better way to do that than with a class of modular add-ons that also look really cool?

Companion Cubes

Malka designed a type of “parasitic architecture” to solve both problems at the same time. The design calls for a series of bio-sourced wooden cubes to be mounted onto the structure — extending the useful space horizontally through openings in the exterior.

This extension would also reduce the total energy consumption of the building by a factor of four — its current consumption of 190KWh/sq. meter would drop significantly, to 45KWh/sq. meter.


These cubes will be made from a lightweight-but-strong mix of wood particles and chips which can be easily transported and assembled on site by workers.

Once affixed to the building, they will not only increase living space and allow more light to enter the building, but also allow for an inner garden courtyard on the first floor. The new facade will also be draped with hanging plants, which will make it even prettier.

Living in a park: Sydney’s One Central Park proves cities can be green

Sydney can boast the tallest vertical garden in the world. Completed in 2014, the city’s One Central Park is a towering residential building dressed in dazzling green plant garb.

They’re stuffy, they’re gray, they’re dusty — they are cities. To satisfy our ever-growing need for space, engineers have paved and built over green areas, leaving only a tiny sliver behind as parks. But cities and greenery can coexist marvelously, Parisian architect Jean Nouvel and French artist and botanist Patrick Blank believe. The duo’s vision was proven right in 2014 as Sydney’s 166 meter (544 feet) high One Central Park.

The residential high-rise is part of an “urban village” in downtown Sydney that houses residential towers, shops, and common spaces for artists and architects to enjoy. Cloaked in living greenery, OCP’s facade houses 250 species of native Australian plants hopping from balcony to balcony from a park at the heart of the complex. An assembly of motorized mirrors sprawls at the top to capture and direct sunlight down for the plants to enjoy. And after sunset, the building burst in LED lights designed by lighting artist Yann Kersalé to be renewably-powered.

The complex includes two residential towers atop a five-story Central shopping center. The western tower is 84 meters (275 feet) high and accommodates 240 homes, while the 117-meter-high (383 feet) eastern tower contains 383 apartments — including 38 penthouse flats with access rooftop sky garden.

Its name is no coincidence either. The spacious 6,500 square meter (69,965 sq. feet) park at the base of the complex is reminiscent of New York’s famous Central Park. With large open lawns, chessboards, an open air cinema, and spaces for festivals or concerts, it is the architects’ hope that this park will provide a respite from city life just like its counterpart in the US.

But it’s not all relax-this and enjoy-that. OCP and similar concepts serve as a blueprint for what many people hope urban architecture will become in the future. With concrete dominating skylines around the world, green-starved cities bake in their own tiny urban heat islands and smog. Combining built space with greenery could offer a healthy, environmentally-friendly alternative in the future.

“Hydroponic irrigation systems, for one, make it possible to grow a soil-less vertical veil of vegetation in planters and on walls all the way up to the tower tops. The resulting green facades trap carbon dioxide, emit oxygen and provide energy-saving shade,” said said Ateliers Jean Nouvel in a statement.

The concept has had huge success — all apartments list as “sold out” on One Central Park’s website.

KTH researchers develop transparent wood for use in building and solar panels

Wood, one of the cheapest and most widely used construction materials humanity has ever employed,  just had its range of uses expanded: researchers at Stockholm’s KTH Royal Institute of Technology developed a method that makes wood transparent. The method is suitable for mass production, making it even more attractive.

A close-up look at the transparent wood created at KTH Royal Institute of Technology.
Image credits KTH Royal Institute of Technology.

Optically transparent wood is not a new thing, says Lars Berglund, professor at the Wallenberg Wood Science Center at KTH. But it’s usually only been done in microscopic samples intended for wood anatomy studies. Their new process would allow for transparent wood production and usage on a much larger scale than anything ever before attempted.

“Wood is by far the most used bio-based material in buildings. It’s attractive that the material comes from renewable sources. It also offers excellent mechanical properties, including strength, toughness, low density and low thermal conductivity,” Berglund says.

“Transparent wood is a good material for solar cells, since it’s a low-cost, readily available and renewable resource. This becomes particularly important in covering large surfaces with solar cells.”

These transparent panels can also be employed as windows, or used to create semitransparent facades to allow light in while also maintaining privacy.

Optically transparent wood is actually a type of wood veneer from which lignin, a structurally-important component in the cellular walls of trees, is chemically removed. The resulting porous veneer substrate is saturated with a transparent polymer and the optical properties of the two materials are then matched.

“When the lignin is removed, the wood becomes beautifully white. But because wood isn’t not naturally transparent, we achieve that effect with some nanoscale tailoring,” Berglund adds.

“No one has previously considered the possibility of creating larger transparent structures for use as solar cells and in buildings.”

Wood is a renewable resource, but that doesn’t mean we’re doing it substantially  — we have to grow and harvest it accordingly, not by logging away, chainsaws blazing, at the forests around us. The KTH team is now working on ways to improve the transparency of their material and on scaling-up their production method.

“We also intend to work further with different types of wood,” Berglund concludes.

The full paper, titled “Optically Transparent Wood from a Nanoporous Cellulosic Template: Combining Functional and Structural Performance” was published online in the journal Biomacromolecules and can be read here.

Termites know more about ventilation that human architects

The humble termite only has its body, saliva and some soil to work with, and the only blueprints it has are instinctual, based on variations in wind speeds and fluctuations in temperature as the sun rises and sets. Working with such limited resources, they still erect monumental mounds that, a new study reveals, rely on a surprisingly well-tuned mechanism for efficient ventilation, something architects today still struggle with.

Led by L. Mahadevan, Lola England de Valpine Professor of Applied Mathematics, of Organismic and Evolutionary Biology, and of Physics, a team of researchers that included Hunter King, a post-doctoral fellow and Samuel Ocko, a graduate student, both in the Mahadevan lab, has for the first time has described in detail how termite mounds are ventilated. The study reveals that the structures act akin to a lung, inhaling and exhaling once a day as they are heated and cooled.

Thermal images superposed on a photograph of a termite mound (photo 1). At night (left side) the flutes are cooler, so the air first moves down them and then up the central core. During the daytime (right), the warmer air reverses the process, moving air up the flutes and then down the central core. Occurring once a day, it allows CO2 from deep inside the mound to surface and diffuse through the porous walls (photo 2). Thus the mound works like a slowly breathing lung, powered by daily temperature oscillations.
Credit: Hunter King and Naomi Ocko

The study is described in an August 31 paper in the Proceedings of the National Academy of Sciences (USA).

“The direct measurements essentially overthrow the conventional wisdom of the field,” Mahadevan said. “The classic theory was that if you have wind blowing over the mounds, that changes the pressure, and can lead to suction of CO2 from the interior…but that was never directly measured. We measured wind velocity and direction inside the mounds at different locations. We measured temperature, CO2 concentrations…and found that temperature oscillations associated with day and night can be used to drive ventilation in a manner not dissimilar to a lung. So the mound ‘breathes’ once a day, so to speak.”

On a trip to the National Center for Biological Sciences in India five years ago, Mahadevan was surprised to learn that many of the theories about how exactly the termites’ mounds function had not been rigorously tested. Working with Scott Turner, an Associate Professor at SUNY College of Environmental Science and Forestry, and author of a book that examines animal-built structures, Mahadevan, King and Ocko put together a plan to set out to find more definitive answers.

“It occurred to us that the internal flow profiles predicted by different potential mechanisms qualitatively disagree with each other,” King said. “By measuring them directly, we could easily identify the right one. The hard part was figuring out how to sensitively measure these small flows in a confined space defended by glue-and-mud-excreting termites.”

Over a period of several weeks they used a series of custom designed probes to conduct a variety of tests on both live and dead mounds that included temperature readings during the day or at night, covering the mounds with tarps, blowing air over the structures and even using vacuum cleaners to test suction throughout it’s internal passages.

“After months of hard thought and preparation, it all comes down to hiking through the woods at 4am with a laptop, a lantern, custom-built electronics, and a hole saw,” Ocko said. “The ‘aha’ moment made it all worth it.”

As they found out, the ventilation mechanism is in large measure built into the mounds themselves. There is a large central chimney that spans from the gallery — the underground chamber where most of the colony lives — to the top of the mound. The interior, structural walls that make up the core of the mound are larger, bulkier and more resilient, but the exterior ones are far thinner. While impermeable to winds, these outer walls allow for an exchange of gasses with the environment.

The interior structure of a termite mound.
Image via matnkat

During the day, Mahadevan explained, as sunlight either directly or indirectly warms the mound’s outer walls, the air inside warms, causing it to rise.

“What you get is a convection cell,” Mahadevan explained. “The warm air can’t move through the walls quickly enough, but it has to go somewhere, and the only possibility is for it to go down into the interior through the central chimney. At night, as the exterior cools, the airflow reverses, and it pulls the air up from the central part of the mound.”

The end result is that while CO2 concentrations during the day can reach up to four or five percent in the center of the mound, the airflow at night pulls the gas to the exterior walls, where it can escape by diffusing through the wall.

“But what’s remarkable here is how the termites are using transients. The temperature outside the mound is oscillating, and they have developed a method to harness that to ventilate their mounds.” Mahadevan said.

While the study reveals for the first time how termite mounds truly work, it may also offer lessons human architects could benefit from.

“In a large building like the one we’re sitting in we have windows and doors that allow us a certain amount of seclusion and privacy, but that also means you have a harder time pushing air around from one part of the building to another,”

While the notion of designing buildings that can be more efficiently ventilated is not new, the principles described in the study might offer new ways to think about such passive ventilation systems.

“Could you drive large scale flows through a building like this one by cleverly opening and closing doors and windows ?” Mahadevan asked. “Rather than spending a great deal of energy for a fan and air conditioning in every room, with the end result being that some people are too hot and some people are too cold… perhaps we should think of the entire thing as a system and these new measurements suggest that if the architecture is appropriate, ventilation can occur by using environmental transients — something for us to think about.”

 

Shorties: China building falls over like a brick

This isn’t news, as it happened two years ago, but it’s just mind blowing. This almost finished 13 story high building in Shanghai collapsed like a domino piece, and if others were built closer to it, the domino effect would be complete. This gives kind of a whole new meaning to the whole ‘made in China’ thing, doesn’t it ?

After seeing this, one can only imagine what would China do if faced with a threat like the one the Japanese faced. Thankfully, they’re not, but I really hope this was an isolated case and not a general thing plus some bad luck… because that would be really bad.