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23 sustainable building materials for an eco-friendly house

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sustainable house construction
sustainable house construction

Photo by USAID on Pixnio

Building houses has a tremendous environmental impact. Almost 40% of both total energy use and greenhouse gas emissions in the US come from the building sector. In addition, building a house uses a lot of water and produces a lot of waste. Choosing sustainable building materials can reduce all these impacts.

In some cases, building an eco-friendly house can mean using and updating ancient techniques and materials. Innovative new sustainable construction materials for walls, floors, roofs, and insulation have become available in recent decades, with more on the horizon.

It’s a mistake to hold out for anything perfect. Some of the following materials may be suitable in one climate but not another. Some environmentalists may quibble with a few of them. But if nothing is absolutely sustainable yet, these materials offer significant environmental benefits.



Traditional sustainable building materials

People have been building houses since before the dawn of history. They have mostly used locally available materials.

Some of the following materials will be familiar because they’re still common in American houses. Builders have started to rediscover others.

Adobe

adobe building. eco-friendly building materials

An adobe building in Santa Fe, New Mexico / Wikimedia Commons 

Long before a software company adopted the word, adobe meant an ancient building material made of dried mud. Adobe houses are common in the southwestern US. In fact, adobe works best in arid climates. Excessive humidity damages it.

Adobe bricks can be made from clay or sandy mud, depending on what’s locally available. They also need straw or some kind of binder. Traditionally, once mixed and formed into bricks, they must dry in the sun for about a month.

Because adobe exterior walls are load bearing, adobe buildings rarely exceed two stories. They need a finish such as mud plaster or stucco to protect them from water.

Modern manufacturers might add some cement or lime or asphalt for waterproofing. The bricks might be mechanically compressed instead of hand made and/or dried in a kiln. These techniques add some emissions. Even with these innovations, adobe remains a sustainable building material.

It’s not strictly necessary to form adobe into bricks. So-called puddled adobe entails mixing the material and piling up lumps to make an earthen wall, which dries in place.

Bamboo

Bamboo might not come to mind as a traditional building material in the US or Europe, but it certainly is in Asia.

It is one of the most sustainable plants in the world. Growing bamboo doesn’t require much in the way of irrigation or fertilizer. Harvesting bamboo doesn’t kill the plant.

Bamboo can substitute for anything that can be made of wood. A sustainable house could conceivably have a bamboo frame, walls, floors, cabinetry, and furniture. And construction workers could use bamboo scaffolding to build it.

Bark siding

Siding and shingles made from chestnut bark used to be common in the US until blight killed off all the chestnut trees. Lately, with growing interest in sustainable building materials, bark siding is coming back into favor using poplar bark.

The bark comes from timber cut for lumber. Very often, bark is discarded as a waste at the logging site. At best, the sawmill makes mulch from it. Making it into a building material is a way of treating a waste as a resource.

Clay brick

Clay bricks are an ancient building material that, unlike adobe, is suitable in a wide range of climates. Craftsmen used to make them by hand and dry them in the sun. Today’s manufacturers fire them in kilns. That is, factory-made bricks cause some greenhouse gas emissions. Just not enough to disqualify bricks as sustainable building materials.

Bricks require less maintenance than many other building materials. They require no treatment to ward off fungi or pests. Brick buildings last a very long time, or they can. These features offset the effects of manufacturing the bricks.

Americans demolish too many buildings too soon. In the case of brick buildings, the bricks are reusable. Used bricks on a new brick building carry none of the possible negatives of new bricks.

Cob

 

cob house. sustainable building materials

21st century cob building in East Devon, England / Wikimedia Commons

Cob is an ancient English way of making dirt houses. It comprises lumps of clay, sand, and straw, generally mixed by stomping on it with the builders’ feet. Shoes are optional. To this day, builders of cob houses build walls a handful at a time, carefully smoothing out each lump. (Cob is an Old English word for lump.) Natural materials plus not using energy-sucking equipment makes an eco-friendly house.

British cob houses as much as 500 years old still exist with people living in them. The same technique developed independently in other parts of the world. Yemen has some 700-year-old cob buildings that stand nine stories tall.

In 2002, a cob pottery shed survived the wrath of Hurricane Lili when most other buildings in the neighborhood collapsed.



Cork

Cork comes from the bark of a cork oak tree. The trees typically live for at least 250 years. Using special axes, highly skilled workers strip the bark from the trees as they have for hundreds of years. Each tree can be safely harvested up to 20 times in its life and produces several hundred kilograms of cork at each harvest. The bark grows back quickly.

Most cork becomes stoppers for wine bottles, but it has many more uses. The ancients used it for floors and insulation. Modern architects have turned to it as an eco-friendly building material for those uses and more since the turn of the millennium. At least one company can even make material suitable for walls from recycled wine corks.

Cork has an extremely low density. It floats. In fact, it is impermeable both to liquids and gases. That means it doesn’t rot. It doesn’t absorb dust, either, which protects against allergies.

Cork’s membranes are very flexible. And so cork can withstand great pressure and then return to its original form. It also resists wearing

Because cork doesn’t conduct heat, sound, or vibration, it is very useful for insulation and soundproofing. It’s also a natural fire retardant. If it does burn, it doesn’t release toxic gases

The cork oak grows only around the Mediterranean Sea. Portugal supplies about half of the world’s cork supply. Its first laws protecting cork trees date back about 700 years. For the past 100 years or so, it has been illegal to cut down a cork oak in Portugal, with very few exceptions allowed. For example, when one dies. New cork trees are planted every year to ensure that demand for cork can’t exceed supply.

Green roof

Green roof on Chicago City Hall.

Green roof on Chicago City Hall / Wikimedia Commons 

Living roofs, best known now as green roofs, have been around for millennia. The famous Hanging Gardens of Babylon may have been an example. Autocratic rulers like Nebuchadnezzar can do whatever they want for aesthetic pleasure.

Ordinary people have made living roofs for more mundane reasons. Roofs of sod and grass provided insulation for various peoples from the Vikings to settlers of the American prairie. They count doubly as green building materials.

During the oil crisis of the 1970s, Germany first began to investigate green roofs as a means of saving energy. Chicago Mayor Richard M. Daley saw a green roof there and ordered a one installed on City Hall in 1998. The idea spread to other American cities, although New York’s Rockefeller Center has had one since the 1930s.

Green roofs have numerous environmental advantages. In densely populated urban areas, these advantages include reducing heat islands. A green roof might be as much as 30-40º cooler than nearby conventional roofs.

Enough of them can actually reduce temperatures city wide. Plants can include food crops. They can either be donated to a local food bank or sold in grocery stores, farmers’ markets, or to restaurants.

They are, of course, heavier than conventional roofs. Whenever they’re intended to replace a conventional roof on an existing building, it’s necessary to add some kind of structural support to it.

Rammed earth

rammed earth home. sustainable building materials

Rammed earth home / Brant Fetter via The Agency Los Cabos 

One of the most ancient building techniques, rammed earth, dates back to Neolithic times. It requires no heavy machinery and depends on locally sourced materials. Therefore it has low embodied energy and produces little to no waste. This sustainable building material works best in climates with moderate temperatures and high humidity.

Rammed earth construction begins with erecting a frame. Nowadays, plywood is the frame of choice. A small amount of clay, gravel, and a stabilizer is placed in the frame and tamped down to about half its original volume. The process is repeated until the wall reaches the desired height. Then the builder removes the frame. The Great Wall of China is a rammed earth structure, which testifies to its durability.

Several modern techniques improve the thermal characteristics of rammed earth construction. So-called stabilized rammed earth adds cement to the mixture, which further stabilizes the wall. Unfortunately, that adds embodied energy and diminishes the sustainable characteristics of the rammed earth.

Straw bales

If you travel through farm country, you have probably seen straw bales in the fields but might not recognize that they can be a good eco-friendly building material. The straw can serve as animal bedding and mulch. Some farm animals can eat it, but it provides less nutrition than hay.

After farmers use all the straw they can, the rest becomes a waste problem. Eventually, it will become economically feasible to make ethanol from straw and other agricultural waste. Until then, the building with straw remains its best use. Straw bales have little embodied energy since nature does most of the work.

Don’t be thinking of the Three Little Pigs! The first little pig may have built an eco-friendly house, but it wasn’t very sturdy. But if properly maintained, straw bale walls can last for a hundred years. Then, farmers can plow them back into the ground. Straw walls are at least 18 inches thick. That makes them a great insulator but also reduces the usable interior square footage.

Contrary to what you might suppose, straw bale walls are also flame retardant. They are too dense to catch fire once the source of ignition is gone.

Terrazzo

Neolithic people embedded crushed limestone in clay floors as early as the 9th century B.C. Modern terrazzo uses techniques perfected by Italian craftsmen in the 18th century. They embedded marble chips in a base of mortar.

Newer technology allows it to be made in sections surrounded by metal strips. It’s an eco-friendly building material because it often uses scrap marble, other stone, or even glass, keeping waste out of landfills.

Once used exclusively as flooring, terrazzo has begun to appear on countertops and walls.

Wood

Wood is a traditional building material that comes from a renewable source. Unfortunately, not all the forests that provide lumber are sustainably managed. Wood may or may not be a sustainable construction material depending on where it comes from.

Reclaimed wood always counts as sustainable. It can give a classy appearance that new wood can’t match. It probably isn’t as strong as new wood. Therefore, it is necessary to assess each piece’s integrity and suitability. But if it won’t work for one use, it might work for another.

Wool

A wool blanket or sweater can make you toasty and warm on a cold winter day. Wool can do the same for your home when incorporated into the insulation. Except, of course, you’d never choose a wool blanket to keep you cool in the summer. Your home’s insulation does just that.

Wool is sustainable because it’s renewable. Each sheep must be sheared many times in its life.

It is safer to install than fiberglass insulation. And when wool insulation reaches the end of its life, it’s compostable.

On the other hand, wool has to be treated to repel insects or prevent fungi from growing. Its eco-friendliness depends on the processes and chemicals used for the treatment.



Newer sustainable building materials

Recently developed sustainable construction materials offer a variety of benefits. Some modify traditional materials in ways that give them new environmental advantages. Some are made of waste material that would otherwise go to a landfill. And some even suck carbon dioxide from the atmosphere.

A few of the following products are still under patent. They can probably not enjoy widespread use until the patents expire and other manufacturers can start making them.

Acetylated wood

Acetylated wood bridge. green building materials

Acetylated wood bridge near Sneek, the Netherlands / Wikimedia Commons

For all its excellence as a sustainable building material, wood decays easily. Recently, acetylated wood has become economically viable. To oversimplify, pickling soft wood in acetic hydride (in other words, vinegar) makes it impossible for the cells to absorb water. In turn, that makes it impossible for the wood to rot, warp, swell, or shrink. Termites lose interest in it.

And although the vinegar isn’t any of the kinds you keep in your kitchen, it is non-toxic. With no toxic chemicals in acetylated wood, no toxic chemicals can leach out. When acetylated wood reaches the end of its useful life, it is completely biodegradable. Like any other wood, it is compostable or becomes useful for mulch.

Concrete substitutes

Concrete is another ancient building material. Nowadays, it’s about 10-15% cement, 60-75% aggregate, and 15-20% water. Each pound of concrete manufactured produces almost a pound of carbon dioxide. We use so much concrete that it makes the construction industry a major polluter.

If the aggregate comes from limestone quarries, add the environmental impact of mining to that of the cement. Using recycled concrete for aggregate eliminates mining, but it takes energy to remove the contaminants to make it suitable.

Most of the problem with concrete comes from production of cement. But it also accounts for about 10% of the water used by industry worldwide. Concrete substitutes make more sustainable building materials. Some still require cement. Others don’t.

Ashcrete

It’s possible to create sustainable building materials from the worst of environmental headaches.

Burning coal produces coal ash, which has caused multiple environmental problems. For years, state-of-the-art disposal involved soaking ash in water and storing it in lagoons. The practice has resulted in some spectacular failures when the lagoons ruptured and dumped ash into nearby rivers.

Many environmentalists regard coal ash as a toxic waste. That’s a good way to annoy scientists who actually work with it. It can be a valuable resource for all kinds of products—including sustainable houses.

Coal ash has two major components. Fly ash travels up the smokestack. Scrubbers now keep most of it out of the atmosphere. Bottom ash remains at the bottom of the furnace.

Ashcrete uses fly ash as a major component, some bottom ash, borate, and a chlorine compound. Using it in place of cement keeps cement’s emissions out of the atmosphere. What’s more, ashcrete can actually remove carbon dioxide from the air. It also needs less water.

If the world succeeds in weening itself from coal, after a while there will be no raw materials for ashcrete. But it will have served its purpose. Other concrete substitutes will remain.

Ferrock

Ferrock. sustainable building materials

Ferrock / Green World Vision via Facebook

Add Ferrock™ to the number of inventions made by accident. Dr David Stone was actually looking for a way to keep iron from rusting. Like ashcrete, Ferrock uses a waste material: steel dust.

It’s carbon negative. That is, where concrete emits carbon dioxide as it dries, Ferrock absorbs carbon dioxide from the atmosphere. It is stronger and more flexible than concrete.

As a fairly new and untested green building material, it’s still relatively expensive, available only from a single company, and limited in application.

Hempcrete

Hempcrete uses the woody inner core of the hemp plant. It has a higher silica content than any other plant fiber. Hemp fabric comes from the outer fibers. The core makes excellent animal bedding, but for fabric making, it amounts to a waste byproduct.

Unlike ashcrete or Ferrock, hempcrete and woodcrete require some kind of lime-based binder. If it’s cement, they require as much of it (10-15%) as concrete does. Hydrated lime makes a more eco-friendly alternative to cement, but it has its own disadvantages. For one thing, it is less strong. Even with cement, these concrete substitutes are sustainable building materials for using various organic wastes as aggregates.

For a sustainable house, hempcrete makes an excellent insulating filler within a frame but is not used as a structural element. After mixing, it can be stuffed into the frame by hand. For exterior walls, it is finished to look like stucco.

It seems like a very recent material, but hempcrete has been found in a 1,400-year-old bridge abutment in France.

It weighs much less than an equivalent volume of concrete. Blocks of fully cured hempcrete actually float in water.

Hempcrete leaves behind no waste. Whatever is left over at a building site can simply be plowed underground to compost.

Timbercrete

Hardwood sawdust constitutes about half the volume of the dry ingredients in Timbercrete™. The rest is sand and cement or hydrated lime. Actually, Timbercrete is the name of the Australian company that first developed it. Since it’s a trademark, it would probably be better to refer to it generically as woodcrete.

Compared to concrete, woodcrete is stronger, lighter, and a better insulator. It’s also easier to work with, as it can be installed with screws or nails. And like Ferrock, it absorbs carbon dioxide.



Enviro Board

Enviro Board™ is another patented product, this time based on a process invented in Sweden in the 1930s. It’s a panel made from agricultural waste that can substitute for plywood, drywall, and similar materials used for walls, door cores, insulation, office partitions, etc.

For building sustainable houses and other structures, it can replace wood, brick, and concrete with wastes that might otherwise be burned. Therefore, it’s a sustainable building material that prevents massive amounts of greenhouse gases and lessens deforestation.

Mass timber

Although wood has been used for building for millennia, new techniques collectively called mass timber (short for massive timber) enable wood to take over functions of concrete or steel.

One, cross-laminated timber (CLT), originated in Austria in the 1990s.  It involves trimming lumber boards, drying them in a kiln, and then gluing them together to create slabs about a foot thick. They can be used for walls, floors, and ceilings. A 280-foot tall CLT building has been built in Norway. Taller ones are planned.

American building codes hamper adoption of mass timber, but the lumber business in the US has been in crisis long enough that the industry is looking for new uses for wood in construction. Timber states such as Washington and Oregon have updated their building codes to incorporate mass timber.

Unlike the familiar and highly flammable stick-frame houses with 2x4s, it is very difficult to ignite mass timber. The wood both sequesters carbon and avoids the greenhouse gases emitted in construction with concrete and steel. These are only two of several environmental advantages that make mass timber a sustainable construction material.

It does, however, still require cutting trees, and living trees make better carbon sinks. Realizing the full advantages of mass timber requires a commitment to sustainable forestry.

Mycelium

I have written about using mycelium in packaging and as a leather substitute. It amounts to the root system of fungi. Combine mycelium and agricultural waste in a mold, and it can grow to any shape desired. Including blocks suitable for building material.

When derelict wood houses must be demolished, the wood has usually gone to a landfill. Instead, it can be ground up for a growing medium for mycelium. That give mycelium an additional kind of waste it can recycle.

So far, most buildings with mycelium have been temporary structures. And when they’ve fulfilled their function, they have been composted. Imagine the advantages of, say, a mycelium Olympic site. Some firms are researching how to incorporate it into permanent buildings.

Precast concrete slabs

It’s a mistake to write off concrete entirely as a sustainable building material. Aside from the environmental concerns of the cement in concrete, it makes a difference where the concrete is cast: onsite or at a manufacturer’s site.

With onsite casting, weather conditions can affect the curing process and introduce cracks or other structural faults. Stormy weather prevents onsite casting and therefore causes construction delays. Casting at the manufacturer’s plant enables curing to happen in a controlled environment regardless of weather conditions.

Precast concrete slabs may be solid concrete or have large hollow air pockets like bricks or cinder block. They can be used for walls, floors, or roofs. The factory needs to be located reasonably close to the building site to prevent transportation costs from negating the environmental advantages.

Recycled materials

Recycled plastic, steel, or rubber can play significant roles in sustainable construction materials.

Composite lumber such as Trex™ has become a common eco-friendly material for decks and other structures. It is made from recycled plastic films, such as all those single-use shopping bags, and scrap wood. Other uses for recycled plastic include making bricks or as an additive for concrete.

Unlike paper or plastic, metals do not lose any properties when recycled. Steel, in fact, is recycled more than any other substance. Year after year, the amount of recycled steel surpasses all aluminum, glass, paper, and plastic combined. The environmental impact of recycled steel is much lower than that of making new steel.

Houses use steel less than other building materials. Whatever steel goes into constructing one might as well be recycled.

Recycled rubber tires can find uses such as wheelchair ramps, flooring, roofing, sealants, and waterproofing membranes.

Shipping containers

shipping container mansion. sustainable house

Shipping container house of less than modest size! / Fin Fahey via Flickr

We don’t often think of shipping containers as single-use items, but many of them make only one trip. Plenty of others are retired when still in good condition. So why not recycle them to make houses? It’s yet another way to transform wastes into sustainable building materials.

Shipping container homes fit well with the tiny house movement. They are usually 8 feet by 20 or 40 feet, The smaller offers about 160 square feet of space for living and the larger about 320 square feet.

Or sometimes people combine several shipping containers into a single structure. Stacking them can make a tiny apartment building. Other layouts can result in mansion-sized houses.

Therefore, shipping container homes can be as simple or elaborate as desired.

Structural insulation panels

Structural insulation panels (SIPs) basically amount to a sandwich of some kind of insulation between two plywood boards. The most common insulations are either expanded polystyrene or polyurethane. SIPs provide the ability to make sturdy, well-insulated buildings with reasonably thin walls and roofs that do not require stick framing.

SIPs are made in factories and shipped to the building site. They come in sizes from 4 feet by 8 feet to 8 feet by 24 feet. Construction workers cut openings for windows and doors with a saw.

So how are SIPs a green building material? It takes less time to erect a SIP house than a standard frame house. It also requires less water and less wood. At the end, there is less waste, although the plastic insulation makes any waste difficult or impossible to recycle.

Eco-friendly houses made with SIPs cost more than conventional construction, but it also costs much less to heat and cool them.

The post 23 sustainable building materials for an eco-friendly house appeared first on Sustaining Our World.


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