we shape our buildings; thereafter they shape us.

-winston churchill, 1943

our buildings define us. not only do we need them to survive, but—consciously and subconsciously—they shape our worldview. as world temperatures rise, we will rely on them even more in the face of oppressive summer heat, intensifying blizzards, and other extreme weather events. but air conditioning buildings and producing concrete—the most important building material—amount to 12% of the world’s total greenhouse gas emissions. so to move our planet forward, we need scalable innovations in how we build and what we build with.

the innovation center at the pontificia universidad católica de chile looks stylish, promotes more collaboration than a traditional office building, and cuts electricity consumption by two-thirds just because it uses fewer but larger glass windows. the canada-based company carbicrete has developed concrete that actually captures concrete from the atmosphere. and the best part is: these solutions are easy to implement! some might even call them common sense. by expediting the rollout of these production and architectural techniques, we can drastically limit the damage of climate change and help provide for a better future.

full transcript below:

francisco camacho, host:

i want to take you back to about a year ago when i was studying in santiago, chile. everyone—and i mean almost literally everyone—in chile had bemoaned that the mountains didn’t have snow year-round anymore. in the summer, it now melts. even 6 years ago, there was always a little snow visible at the peaks year-round. unlike in the united states, the chileans never gave me any sense of climate change skepticism: they knew for certain that the increased co2 in our atmosphere was warming the earth and melting their beloved snow.

so, how do we stop the snow from melting? obviously, tackling climate change is an enormous problem with almost-infinite components, but i want to focus on one aspect that is rarely mentioned: our buildings. according to a 2022 study from researchers at the national renewable energy laboratory, energy generated for air conditioning buildings accounts for 4% of the world’s annual greenhouse gas emissions. moreover, the world’s most important building material, concrete, is incredibly carbon intensive: concrete production accounts for a whole 8% of global emissions. so, these are the two questions i come to this story with: how can we design buildings to reduce greenhouse gas emissions and how can we make more eco-friendly concrete?

first, let’s talk about the building’s design—the architecture. for this, i want to take you back to chile. it was june of 2022 and my brother had just arrived to visit me. since my brother was—is—studying architecture, i took him to the main campus of the pontificia universidad catolica de chile, where i was studying, and brought him to what at first just looks like a concrete cube near the entrance. it’s called the innovation center and when you enter onto one of the large balconies you get a view of the andes mountains that is hardly paralleled anywhere else in the city. it was winter in the southern hemisphere and i remarked to my brother that i was very happy to see snow on the mountains—again, i had done all summer hardly seeing any.

my brother pointed out some interesting features of the building’s architecture. mainly, there weren’t many windows, and the large ones behind the balconies were well-shaded from above. this meant that sunlight rarely came into direct contact with glass in the building even as a healthy amount of natural lighting did come through. this, my brother observed, must save dramatically on ac costs. that’s because the greenhouse effect caused by sunlight hitting the glass would warm the building, meaning the ac needs to run more intensely to keep the same temperature. think i’m exaggerating? the average glass office tower consumes 120 kilowatts of electricity per square meter per year. the innovation center uses only 40 kilowatts per square meter per year. so this design cut the building’s electricity consumption—and therefore long-run carbon emissions—by two-thirds!

but not only is the building environmentally friendly, it’s practical and good looking! here’s the architect of the innovation center: chilean architect and winner of the pritzker prize, alejandro aravena in his ted talk:

alejandro aravena, architect:

it is accepted that for such an aim, knowledge creation, interaction among people, face-to-face contact, it’s important, and we agreed on that. . . . and what we did was, let’s have an open atrium, a hollowed core, the same collection of floors, but have the walls and the mass in the perimeter . . . you are able to see what others are doing from within the building, and you have a better way to control light.

francisco camacho:

so by putting the building’s essentials—plumbing, cables, etc—in the walls and leaving the center open, not only does sunlight reflect away from the building but people can more easily communicate on their work.

but as i said, the practicality is only one aspect: the innovation center looks good, too! one might see in the innovation center similarities to the monumental architecture of louis kahn. in the 60s and 70s, architects focused on making buildings feel lighter with thinner walls and more glass, but kahn saw the importance of monumentality, which in turn contradicted the course of architecture at the time. aravena, like khan, uses concrete to highlight light, shadow, and the authenticity of a building.

to hear his take, i sat down with chilean architect marco diaz. this is what diaz had to say about the innovation center and its architect aravena:

marco diaz, architect (translated):

i believe in itself, the building presents an important aesthetic impact, from the point of view that it comes out as an innovator. in this way, with the objective being to build an innovation center, its aesthetic, its tectonic, its form, and its proportions are very distinct from what is typically done. from that point of view, the aesthetic point of view and from the scale of how he works, he is very innovative. i think he has a first objective completed in some way because of what he was assigned and the product he created.

francisco camacho:

okay, so that’s the architecture question out of the way: by following the models of architect alejandro aravena and the innovation center, we can design more environmentally-friendly, collaborative, and stylish buildings! but this still leaves one big problem: the innovation center is made almost entirely of concrete. and concrete burns a lot of carbon emissions—8% of all annual greenhouse gasses. in fact, if the world’s concrete production was its own country, it would only be behind the us and china in terms of greenhouse gas emissions.

well, for this we come to part 2 of our solution to green buildings: the material itself. on paper, there is actually an almost-miraculous solution for concrete’s pollution problem: carbon capture. one of the companies leading this charge is the canada-based carbicrete. i wanted to understand just how their product worked.

martin escarbelt, carbicrete:

you mentioned that concrete is a very carbon-intensive battery, which is true and it is not mostly due to the presence of cement within it. cement’s production process is extremely emissions-heavy. so we say that typically for a traditional cement manufacturer, there is 800 kilograms of co2 that are emitted. and that is in the origin of the fossil fuels that are burned and because of the chemical process that happens in the kiln when it is being produced.

so at carbicrete we decided to tackle the root of the problem by entirely removing cement from concrete. but it is important to note that cement is extremely important in concrete. we usually say that cement is to concrete what flower is to bread. you cannot do with it – without. and so we replace the cement with a byproduct from the steeling industry that’s at the moment in 2023, and it has always been a waste for steel manufacturers. once the concrete is a phone using steel slag, we use the same processes. the same machinery. we place the concrete products into a curing chamber. so curing is a fancy world to say solidifying. it’s the process that needs to take place to give the concrete – insert strength. and once in there, we inject co2 into the chamber that will react chemically with the steel slag to form caco3—calcium carbonate.

this makes the concrete – its strengths up to 30% better than conventional concrete. and co2 is as a consequence permanently within the concrete and removed from the atmosphere.

francisco camacho:

absolutely. it – it does sound very much on its face like a win-win. but my question is, you know, is it, is it scalable? like, is it actually, is it hard to reproduce this on a wide scale or is it relatively easy?

martin escarbelt:

yes, so it is a scalable solution. there is some limiting factors. as they just said, it is – what we are using is a byproduct of the steel industry, which means that we need to have a steel industry in the neighbor – in the neighborhood. but fortunately, most of the big markets that we’ve targeted have that. so the us produces a lot of steel: canada, europe, china, india. so that’s something to keep in mind, but we are able to scale up. we have just proven our technology in an operational setting in quebec where we’ve been producing for quite some time, thousands of blocks every day and we are in the process of scaling up at the moment in the same facility and now we are ready to – we have this province solution, this proven recipe – we are already ready to implement the technology elsewhere and that includes canada. so quebec, ontario for now, the us, europe, and india, as i said, as well as other places.

francisco camacho:

so carbon capture concrete, like what carbicrete makes, is 30% stronger, cheaper, and uses waste from steel manufacturers. it seems pretty amazing. but at this point, i was worried that there might be a catch. i can consider what i like to call the electric vehicle problem. evs are way better for the environment over the course of their lives than a typical gas-fuelled car is. however, because of how much energy it takes to make a new car of any model, the environmentally optimal option is usually to just ride gas-guzzling cars until they’re broken for good before buying an ev. believe it or not, this isn’t a problem with carbicrete’s carbon-negative concrete.

martin escarbelt:

first off, what we do – what we do most of the time is retrofit existing plants. so we don’t need to build an entire new thing every time we want to implement our solution. and what we are – and the solution we are using is not carbon-intensive as of itself. and we are very attentive to the authentication and verification processes. we’ve performed fcas and other analysis, and we are communicating on a case-by-case basis to make sure that the carbon reduction and the carbon removal is verified as real.

and what we can reasonably achieve once the plant is operational is 250% reduction in carbon emissions. so both through carbon emissions avoidance and carbon removal and so we can just try to visualize a concrete block. we can achieve carbon footprints as low as -1 kilogram per block. which, as we mentioned, is in the carbon-negative zone.

francisco camacho:

there you have it! a combined 12% of the world’s annual greenhouse gas emissions—4% from air conditioning and 8% from concrete production—has the potential to be almost completely eliminated! the technology and designs are already here. so to move our planet forward, we need to lean into these techniques! even though carbicrete is cheaper and aravena’s designs are common-sense practical, change moves slowly on its own. to really make this impact felt, governments, ngos, and ordinary people need to be aware of and promote their use. and heck, by doing this, maybe we’ll come across even better technologies and architectural models.

• most buildings were designed for an earlier climate – here’s what will happen as global warming accelerates. climate change is drastically altering the environmental conditions in which our buildings were designed to function. but how exactly does climate change affect our building materials? 

• 5 ways to make buildings climate change resilient. building for resilience against heatwave, cyclones, coastal flooding, and extreme cold — what does the future of infrastructure look like?

• an architect with an eye on the environment. increasingly, architects, and builders are thinking about how their creations affect the health of the planet. meet kunlé adeyemi, a nigerian architect who has built his career around that question.

check back tomorrow for more info on what is being explored on the final day of cop26 — and more good reads to keep you informed!

as we move toward urbanization, montreal is a leading city when it comes to this type of innovation. while traveling the city, there are many examples of architecture that have adopted new, green practices, but one of the most striking lies in parc frederic-back.

located in the north-west corner of the city, parc frederic-back is a beautiful piece of urban greenery that spans over 350 acres. this park lies in the middle of the saint-michel environmental complex, the green space is being utilized in a unique way. the park lies on top of the remains of a former quarry and landfill site. creating green space on any old landfill is a win for environmentalists. the most notable aspect of the park are the hundreds of biogas-capturing spheres that dot the land. not only do the spheres collect gas from the earth that is then turned into sustainable energy, they also glow in the dark.

the land has an interesting history tied to it. it has not always been a beloved, manicured green space. its original form was as a limestone quarry for 60 years. it was not loved by the saint-michael community, the neighborhood it is located in. the surrounding residents hated the deafening blows into the earth, and numerous quarry accidents angered them. local protests took place to end work at the quarry. the cries for change were heard, and in 1988 the city of montreal acquired the land from the miron family. it was not yet acquired to be made into a park. according to the city of montreal, it was turned from quarry to landfill by the city, and until 1995 it collected the city’s garbage. during the 90’s, it’s environmental transformation took place. during the renovation, the city called it the “most ambitious environmental rehabilitation project ever undertaken” in an urban area in north america, as reported by the cbc.

one of the first steps to creating an eco-friendlier space was creating a recycling center. the waste treatment and disposal centre was created. then, came the most notable aspect of the park, the alien-like spheres that define the land. montreal-based architecture firms, lemay and morelli, designed the balls for the urban rehabilitation. they created 250 spheres to collect the methane gas that is still being emitted from the remains of the landfill below the surface. about 40 tons of garbage from the landfill still generates fumes and is collected, according to world architecture. from there, the cbc article explains the gazmont power station starts converting into electricity biogas extracted from production wells, which is then sold to hydro-quebec.

the spheres are not only proof of montreal’s dedication to environmentally friendly and sustainable urban planning, but they were created with park-goers in mind. they are safe to be around, and they are interactive. they collect light from the sun on their fiberglass surface, and at night they give off a soft, green glow. when a light source at night, such as a park-goer waving a flashlight, runs across its surface, a multi-colored bright light follows the pattern drawn on by the person. it leaves behind the drawn light pattern and impresses novice flashlight artists. 

marrying an old landfill and a popular park may seem counterintuitive, but the collaboration has created a unique, beloved park in the middle of the saint-michael neighborhood. the transformation of this former brownfield is a feat for the city of montreal, and an example as other cities push to create more urban green spaces. 

as rightly said by linus torvalds, to build for the future, “we needn’t reinvent the wheel every time.” instead, we can take what already works and adapt it to our needs. snøhetta, a norwegian design firm has shown us exactly how we can incorporate culturally and environmentally appropriate designs while catering to social and economic issues. they develop and construct buildings that produce more energy than they consume over the course of their lifetime, such as the powerhouse kjorbo project.

in 2015, they designed the first powerhouse educational building, drøbak montessori school, on a forested site in drøbak, norway. the design is derived from the energy concept, the montessori pedagogy, the physical context and a tight budget. the architecture is considered a social and educational tool, with the powerhouse concept as the main formative element. the rectangular building is positioned close to the forest edges, creating a large outdoor play area in close connection to the surrounding nature. passive measures such as a compact volume, high u-values and materials that are low in embodied energy, ensure the building´s low energy demand.

in the commercial space, in collaboration with arctic adventures of norway, asplan viak and skanska, snøhetta has designed “svart” the world’s first powerhouse hotel, at the foot of the svartisen glacier that runs through meløy municipality in northern norway. “svart” is the first building to be built after the energy positive powerhouse standard in a northern climate. not only does this hotel reduce its yearly energy consumption by approximately 85% compared to a modern hotel, but it also produces its own energy – an absolute “must” in this precious arctic environment, while preserving the natural environment of the site and leaving a minimal ecological footprint.

svart’s identity is inspired by both the unique arctic nature and climate and the hotel’s circular form with 360-degree views. to minimize the environmental footprint, the circular body of “svart” is to be extended from the shoreline by the foot of the almlifjellet mountain and into the clear waters of the holandsfjorden fjord. the circular shape provides a panoramic view of the fjord and an experience of living in proximity with nature. the construction is inspired local vernacular architecture in the form of the “fiskehjell” (a-shaped wooden structure for drying fish) and the “rorbue” (a traditional type of seasonal house used by fishermen). the rorbue reference translates into the hotel’s supporting structure which is built from weather resistant wooden poles stretching several meters below the surface of the fjord. the poles ensure that the building physically places a minimal footprint in the pristine nature and gives the building an almost transparent appearance. the precious nature surrounding the hotel can only be accessed by boat, and there are plans to introduce an energy neutral boat shuttle from the city of bodø to the hotel. 

to reach the powerhouse standard, several cutting-edge design choices have been made. for example, the architects have conducted an extensive mapping of how solar radiation behaves in relation to mountainous context throughout the year to optimize the harvest of energy. the result of the study has been an importance premise for the circular design of the hotel, and both hotel rooms, restaurants and terraces are strategically placed to exploit the sun’s energy throughout the day and seasons. the hotel’s roof is clad with norwegian solar panels produced with clean hydro energy reducing the carbon footprint even further. due to the long summer nights of this area, the annual production of solar energy will be significant. secluded terraces provide a shadow play in the façade of the hotel while also ensuring privacy. the facades protect against insolation from the sun in the summer when the sun is high in the sky, removing the need for artificial cooling. during the winter months, when the sun is low in the sky, the large windows of the façade allows for a maximum of insolation to exploit the sun’s natural thermal energy. materials with low embodied energy have been used to reach the powerhouse standard. 

drawing from snøhetta’s efforts to tackle systemic design challenges while accounting for climate change, social inequity and urbanization, building for the future is an iterative process where we build by the bits and not by the lots. where we no longer employ the cookie cutter approach but build with communities, while integrating the natural environment. particularly in indigenous and fragile lands, constrained by resources, we build communities to enable them to realize their full potential by upholding their culture and dignity while being environmentally responsive. building for the future means creating buildings that matter, buildings that help us envision a future greater than any individual. let us not create buildings of the future. let us build for the future.

students from across the globe are traveling to the heart of the panama jungle to learn everything from the fine points of farm-to-table cooking to the most efficient configurations of iguana farming. taking up residency in the jungle may prompt thoughts of giant bugs, stifling heat, and limited electricity. but what kalu yala’s students really need, according to the design thinking intern katie cappola, is a place to “fight, f*ck and fart” in peace.

jimmy stice, the founder of kalu yala, left it up to the design thinking interns to find a solution for the lack of privacy in this communal living arrangement.

with rest, recreation and human behavior in mind, this semester’s design thinking team faced the challenge of designing residential structures which provide privacy and match kalu yala’s aspirations for sustainability.

privacy

privacy would seem an intuitive aspect of designing homes, but the ranchos the interns call home are without walls, which makes privacy a rare commodity at kalu yala. in fact, interns’ only “private” area on campus — their sleeping space — is either an air mattress or a hammock. while this satisfies the program’s desire for an immersive, sustainable jungle lifestyle, the design thinking interns agreed that everyone could use a little more privacy.

the interns say they have been working on plans for two types of residential structures: “tiny homes,” which eventually will house residents at kalu yala, and smaller “staff shacks” for the full-time staff who currently live on platforms a few hundred feet from town square, the heart of the kalu yala’s campus. these staff shacks will provide staff members with greater privacy and a space of their own, but unlike the tiny homes, they will not have separate bathrooms or kitchens. the design thinking interns hope this will encourage staff members to stay in their positions longer.

“this is a solution to give staff a place that makes them want to stay longer because we do have a high turnover rate,” said cappola, a student at bucknell university in lewisburg, pa. “we’re living in the jungle. living here is hard, and it’s hard to have a family here. those things aren’t exactly conducive here.”

the lifestyle is very public and the interns and staff are constantly interacting with each other and the beautiful valley surrounding them. but they hope to create more opportunities for balance through the construction of these homes and a new round of ranchos. one of kalu yala’s ultimate goals, stice says, is to have people who will call the valley their home, or at least a second home. the interns in design thinking, one of several internship programs available at the institute, recognize this goal will be better met with more opportunities for privacy.

in a community that only has one building with walls — a media center created by a vice documentary team — it seems fairly simple to add more privacy. but at kalu yala, privacy and sustainability are not mutually exclusive. the interns must be sure that their privacy implementations don’t leave a large footprint.

sustainable design

while strech and cappola work on the master plan for the town and address these privacy concerns, design thinking interns david ho and jack fritzjunker are finalizing construction plans for the new round of ranchos, which will greet the nearly 150 interns who arrive at kalu yala in just a few weeks.

the expansion has provided ho and fritzjunker the chance to evaluate and iterate upon past and current rancho designs, which they hope will lead to more stable and sustainable structures. this includes everything from altering the pitch (or angle) of the roof to reduce runoff to using new building materials such as reclaimed wood from the panama canal. beyond these physical changes, however, ho and fritzjunker also spoke with kalu yala staff and interns to discuss ways of improving buildings for the rainy season and how to make sleeping arrangements more comfortable.

“we synthesize all that information into a bunch of design drivers that we can work towards in our design,” ho says. “and then we take those drivers and turn them into physical features in the design that solve the physical problems we’re aiming to solve.”

these design drivers include natural factors such as sun, shade, ventilation, and water access, and behavioral elements like where people choose to sleep or how to manage the mud that constantly seems to end up on everything and everyone at kalu yala. ho and fritzjunker plan to address this grimy reality by creating a mud room, a separate but attached area in the ranchos where people can hang up their muddy clothing before they enter their sleeping space.

this approach, commonly called a “form follows function” model, is one of the guiding tenets of design thinking at kalu yala. for ho, who studies civil engineering in australia, it’s not just about making things ergonomic, structurally sound, or sustainable, but thinking about how to solve problems.

“when you design, it doesn’t make sense to make decisions arbitrarily,” ho says. “you should always be working toward a goal.”

after plenty of drawing, sketching, talking, and iterating with these design drivers, ho and fritzjunker arrived at a list of features that they implemented into their final rancho design. they also have utilized projects from other interns and staff at kalu yala by integrating the often “under-appreciated” guava wood and treating reclaimed wood with a biodiesel product synthesized from waste generated around the institute.

“it’s a lot of improvisation in construction and taking principles that we like and applying them,” ho says. “it’s about looking at the materials and taking into account things like the environmental value, or the embodied energy of a material — something that doesn’t happen a lot,” adds fritzjunker, who graduated from iowa state university in ames, iowa.

ho believes the answer for more sustainable design is not necessarily to focus on regulation, but to envision elegant and simple ways to live better. ho adds that he’s all for novel solutions and likes “thinking out of the box.” but as he and fritzjunker have learned at kalu yala, it should always be about solving problems, whether it’s tackling environmental design, privacy, or how to handle the torrential downpour during the rainy season.

“i was designing for people who didn’t exist and now i’m designing for people who do exist,” ho says. “putting that into practice is one of the most fulfilling things you can do.”

***

note from the editor: a previous version of this story had misspelled a design thinking intern’s name. this version corrects it. we apologize for the error.

the arizona-based start-up company tempe betr-blok is the for-profit arm of a non-profit organization that researches alternative materials for building. frettoloso said the idea of the betr-blok formed from an idea he and his partner developed after there was idea between the two of commercialization opportunity and mass production of a sustainable, affordable building material.

with a diy approach, betr-blok wanted to make the material not only easily accessible, but also easy to build for common hands.

“there is really a community of paper creators,” frettoloso said. “in general, you build a house out of paper and you’re using less labor and less materials.”

the betr-blok is made with paper — yes paper — like shaded paper, magazine, cardboard and regional material. the material of the block has other perks besides its friendly environmental properties — the block is also fire resistant, water resistant, termite resistant and, more importantly, it’s supportive to hold up structures.

“everyone has paper news print and cardboard but they have a unique form of delouse,” frettoloso said.

affordability is another concept frettoloso had in mind while creating the sustainable block. frettoloso said he wanted to highlight not only the environmental aspect of the building block, but also the cost and how it can help homes and businesses save on energy costs.

“lead with costs and those benefits and how people save money,” frettoloso said. “thirty-five percent of the energy that is lost through our house is through the walls.”

the concept over the cost of energy with the betr-blok has been tested by frettoloso and his team over the past several of years. the company recently received a grant from the salt river project, an energy supplier in arizona, to build a 500 square foot test structure of their innovative blocks.

in order to monitor the space, a weather stations and data acquisition was put in place to monitor the blocks. over the course of 3 years, the house was kept at a 76-degree temperature, for a total cost of 18 cents a day. the end of the month bill was 18 dollars. if the calculations of frettoloso’s project were applied to a bigger space, a 2,000 square foot space kept at the same temperature of 76 degrees would put energy costs at 75 dollars a month.

“with 500 square feet, you can easily multiply those numbers to larger houses,” frettoloso said.

the testing and approval of the buildings has been no easy process, with hurdles around each corner that frettoloso and his team have to pay attention to and overcome. fires testing, water penetration and other tests can often eat up a lot of time and money.

“there’s a lot of hoops you have to jump through when you’re dealing with municipalities,” frettoloso said. “it’s necessary, we get it. it’s just really expensive.”

as far the future of betr-blok, frettoloso said he’s optimistic for the next five to ten years, where he hopes his innovation will reach a mass audience who will not only want to welcome more sustainable products to build their spaces, but also save money on monthly and yearly energy costs.

“definitely making it a regional thing,” frettoloso said about the future. “replicate this across the country.”

the idea of taking and implementing the betr-blok across the country is entirely possible, according to frettoloso. by using the base of paper materials and using local materials from a specified place means the block can be recreated from san francisco to oklahoma city to philadelphia. instead of shipping in materials, local economies are able to be used and cultivated by using regional-specific products to contribute to the block.

“the idea is strategically to place this thing,” frettoloso said. “providing the country with different local building materials.”

to learn more about betr-blok, check out this video!

the first animation demonstrates no solar gain at the summer solstice. a south-facing home can be sheltered from the summer sun with sheltering overhangs. this reduces heat build-up during the day, and shifts the peak cooling load to later in the evening as the sun is going down. the air-conditioning savings can be dramatic. the second animation demonstrates the full solar gain at winter solstice that can be utilized in passive solar design. during the winter, as the sun rides lower in the sky, the sun bathes walls facing southwest, south, and southeast in light — to warm the home throughout the day.

not ready to make the investment?  according to the american society of landscape architects, homeowners can take a smaller step in reducing energy consumption through smart tree placement.  when planted strategically, trees can reduce wintertime heating needs by two to eight percent. check out this animation that shows you how.

_{originally submitted july 7, 2011.}

watch an animation that explains how to use the landscape to reduce the energy consumed by a typical suburban home. see how smart tree placement and green roofs and walls dramatically improve energy efficiency. trees are being cut down to make way for new single-family homes, which then often sit on bare lots. these treeless lots not only have negative impacts on the climate, environment, and community health, but they also exacerbate the energy inefficient practices found within homes. this is a major problem given the average american home consumes 70 million btus annually. in fact, taken together, american homes account for 22 percent of total energy use as well as nearly 22 percent of carbon dioxide emissions (1.19 billion metric tons). (sources: the washington post and architecture 2030) mckinsey & co, a management consulting firm, found that energy use in the u.s. could be cut by 23 percent by 2020 by implementing simple energy efficiency measures. while homeowners can take low-cost steps to make the inside of their homes better insulated and therefore more energy efficient, the landscape isn’t often seen as a part of the problem–or the solution. basic green technologies like smart tree placement and green roofs and walls can be used to dramatically reduce energy usage inside homes. if placed strategically, trees can reduce summertime cooling energy needs by 7-47 percent and wintertime heating needs by 2-8 percent. (sources: the washington post and reducing urban heat islands: compendium of strategies. trees and vegetation, u.s. e.p.a.) in addition, well-designed residential green roofs, which are growing popular in some parts of the world, can reduce energy usage in both summer and winter. according to one canadian study, a 32,000- square foot green roof on a one-story commercial building in toronto reduced energy usage by 6 percent in the summer and 10 percent in the winter. similarly, the green roof of the american society of landscape architects (asla) at just 3,000 square feet reduces energy usage by 3 percent in summer and 10 percent in winter. weather, roof, and building size and location also have an impact on the amount of energy savings. lastly, fast-growing green walls can also reduce energy use by providing insulation in the winter and limiting direct sunlight on walls in the summer. in hotter months they also cool air temperatures by up to 10 degrees. (sources: reducing urban heat islands: compendium of strategies. green roofs, u.s. e.p.a. and american society of landscape architects (asla) green roof)