Helps to divide the embodied energy value by expected design life in a particular application to arrive at a fair comparison: e.g. wood vs concrete.

What is the missing variable for the chart, is it energy to weight or...?

If so, it is obvious that concrete, a very heavy material with has (compared to steel) a simple and crude manufacturing process, will be vastly given an unfair advantage.

Light alloys like aluminum are equally disadvantaged. One could build a home with a thin film of aluminum, but you would need many tons of concrete, along with a massive foundation to support it, with concrete.

It seems to ignore the recycilblity ability of the material. Again, high for metals, low for concrete.

Also, the materials list on the left of the chart the last letters in the names are cut off. What the next to the last material "sor.."?? it is the lowest energy but can't figure out what it is...

Concrete has to be considered in many hurricane and sub-tropical zones. Many SIP envelopes use concrete as the best defense against the extreme weather in the southern US. I struggle with the use of concrete but even the highly praised Katrina Cottage uses it as part of their building envelope. These issues have to be considered when you are not in strawbale country.

This is part of a massive greenwashing effort launched in the past 15 years by the cement industry.

To cement manufacturers, whose main fuel is coal, "sustainability" now means incineration of waste as an "alternative" fuel.

Those wastes include all manner of industrial, medical and municipal wastes, including solvents, PCBs, tires, spent fuel oil, you name it.

Good for Treehugger for not being fooled.

If you must use concrete for a project, the only truly sustainable solution is to recycle existing material from demolition.

Let's keep in mind that concrete buildings are among the most revered and beautiful buildings in the history of the world (the Parthenon and other Roman buildings come to mind, and there are many modern examples). Also consider that despite vastly increased production, and with a great deal of effort, the cement industry emits lower carbon dioxide emmisions than 25 years ago. The main point-- those who care about the environment should recognize that as the most durable, flexible and cost-effective building material, concrete is going to play a major role in determining the success of green building initiatives, and concrete sustainable efforts should applauded and supported.

In architecture, so much depends on the design of the buiilding. So many of the low-energy buildings I'm seen use high thermal mass concrete floor slabs as a central component of their design. Clearly many, if not most, of these designers took into account the trade-off between embodied CO2 and operating energy savings and still decided that concrete was a good choice. This might have to do with money, but let's face it, can't do anything without taking that into consideration.

Of course, plenty of designers of low-energy buildings make do with wood, or recycled components (steel). These things need to be evaluated on a case-by-case, entire lifecycle basis. I would think that the embodied energy of wood is highly variable.

Finally, I once read some stuff by an Australian guy who was touting cement formulas which, like lime, actually absorb CO2 as they set. Can't remember the details, or his name. Anyone know who I'm talking about?

The graph comes from this site:
http://www.greenhouse.gov.au/yourhome/technical/fs31.htm
which also has sections on concrete: http://www.greenhouse.gov.au/yourhome/technical/fs34f.htm
and aerated concrete: http://www.greenhouse.gov.au/yourhome/technical/fs34b.htm

So it really is green, is it not?

What's the reference for the embodied energy chart? Timber is listed higher than aluminum, copper, stainless, etc and it is close to glass. Intuitievly, this doesn't seem right.

I'm surprised that no one brought up CO2 -- cement production generates alot of CO2. Yet because it comes from a single point source, it should be the easiest CO2 to sequester.

Let's all remember that Energy is not inherently bad.

fly ash displaces portland cement, which is what needs to fired in a kiln. The kiln is what uses so much enegery. Since fly ash typically displaces about 50% of the portland cement, it is *roughly* 50% greener.

One of the big advantages of concrete is that its attributes--strength, affordability, moldability--allows us to build economically and compactly. A concrete highrise condo, for all its embodied CO2, will probably have a better society-wide carbon balance than a sprawling subdivision of woodframe houses.

I don't think you can compare materials--only buildings.

BTW Glenn, Roman concrete is different than modern cement--it embodies about half the CO2 emmissions. And the Parthenon is marble (maybe you're thinking of the Pantheon in Rome?)

The explanation for the diagram (from http://www.greenhouse.gov.au/yourhome/technical/fs31.htm) says "materials used in the average Australian house contain the following levels of embodied energy", so that explains the apparent anomalies of, for example, timber being higher than aluminium. The table just above that says that concrete uses about 2 MJ/kj, compared to 2.5 for clay bricks, 3.4 for kiln-dried softwood, 11.3 for MDF, 38 for galvanized steel and a massive 170 for aluminium. Of course, they all have very different structural properties, so you really have to compare building techniques rather than materials per se.

I imagine that most of the concrete that goes into the average Aussie house, if it's anything like the average Kiwi house, is used for the foundations and floor slab. When you look at a multistorey dwelling, where one floors ceiling is another's floor, the amount of concrete per dwelling would drop.

So while it wouldn't make much ecological sense to build a detached suburban house entirely out of concrete, a neighbourhood consisting of medium- to high-density homes and workplaces with some concrete construction would compare well in embodied-energy terms with detached homes made of other materials. Then if you add in the known transport efficiencies of higher densities and mixed use, I'd definitely say that concrete has a role to play in green building. Just don't build McMansions out of it!

now hold one there, i am an architectural student, and i can tell you right now you are missing alot of things about this wonderful material:

1: concrete CAN insulate, all you need is the right additives
2: do you want to kill a tree or dig up inanimate earth, perhaps from a brownfield? yeah, thats what i thought...
3: a concrete building will last and last and last... just look at the greek / roman ruins
4: you get ticked off about an underground garage... what about other underground, non-garage structures? and why get mad about garages at all? parking structures create massive amounts of density, so that can be used appropriately rather than having everyone park along a curb and waste space that way
5: you dont take into account other materials which often use concrete in them, such as rammed earth
6: take a structural engineering class, there are things concrete can do that no other material can
7: reinforcing of concrete can be done in some situations with bamboo rather than steel
8: foundations of large, dense, urban buildings such as skyscrapers are impossible without concrete
9: i suggest you look more closely at concrete and its values before dismissing it entirely. there is a time and a place for everything, and it can be a very green material

To answer a previous posted question about the lowest material on the chart being sore... It is actually Stone ... The jpg conversion was not done well. There is a PDF at the site where the chart was aquired.

I agree with the general jist of the post. Concrete uses a lot of energy in production, and we should try to lessen our use of it. However, I agree with many of the comments made by others defending concrete's virtues.

I designed my own eco-house and built it with my own hands. I used a lot of concrete. The main envelope of the house is made of autoclaved aerated concrete. ('Weight for weight, AAC has manufacturing, embodied energy and GH emission impacts similar to those of concrete but can be up to one quarter to one fifth that of concrete based on volume. Its much higher insulation value reduces heating and cooling energy consumption. AAC has some significant environmental advantages over conventional construction materials addressing longevity, insulation and structural demands in one material. As an energy and material investment it can often be justified for buildings intended to have a long life.' http://www.greenhouse.gov.au/yourhome/technical/fs34b.htm) Furthermore, the AAC envelope incoporates some amount of reinforced concrete to increase the strength of the building and make it more resistant to strong winds and earthquakes - I may not live hundreds and hundreds of years but I hope my house will. ('Research by CSIRO has found that the average household contains about 1,000 GJ of energy embodied in the materials used in its construction. This is equivalent to about 15 years of operational energy use. For a house that lasts 100 years this is over 10 percent of the energy used in its life.' http://www.greenhouse.gov.au/yourhome/technical/fs31.htm) Concrete-masonry homes can last a thousand years without any type of maintenance - for a house that lasts a thousand years this is some one percent of the energy used in its life. I also used a concrete slab floor for thermal mass. ('In many cases a higher embodied energy level can be justified if it contributes to lower operating energy. For example, large amounts of thermal mass, high in embodied energy, can significantly reduce heating and cooling needs in well designed and insulated passive solar houses.' http://www.greenhouse.gov.au/yourhome/technical/fs31.htm) My house is a well-designed and well-insulated passive solar house. Furthermore, the concrete I made myself either by hand or with a small electric concrete-maker and wheeled it and spread it by hand ('It may be possible to construct a concrete slab with lower embodied energy than a timber floor if best practice is followed.' http://www.greenhouse.gov.au/yourhome/technical/fs31.htm)
And the foundations of my home are of concrete because there is no real alternative to concrete foundations - I have seen alternative foundations such as stone rubble and sand bags but these are illegal (and I don't quite trust them). And I used concrete for the foundation base of my wind-generator tower - I recycled discarded, concrete chunks from the building of the house by mixing it into the concrete for the wind generator base. I see no problem in recycling concrete - just break it into chunks and reuse it as larger aggregate in concrete foundations or other large concrete jobs.

I do think concrete can be green. Some types of special concrete are green. Some special uses of concrete are green. Some special concrete construction systems are green. But I agree that generalizing concrete as green is inappropriate because generally speaking, blind use of concrete is not green.

3 points to add:

1) Potential to reduce GHGs: the production of 1 tonne of Portland cement releases almost 1 tonne of CO2. The practice of replacing Portland cement with a "Supplementary Cementing Material" (SCM), such as flyash (a by-product of coal combustion), therefore reduces CO2 production by about the same amount. The end-product requires slightly different management due to longer cure times, but less water is used, fewer GHGs generated, and the end-product (depending on the type of flyash) can be quite beautiful.

2) the Australian R&D company referred to in a comment above is probably TecEco. Neat stuff! More of it!

3) BY the way, concrete isn't a benign substance, but then I don't know what human-made material IS, and our urbanized & urbanizing reality dictates that we use it. I love wood, but there are just some structures you just can't build out of sticks! If you were to conduct an LCA on possible material comparisons for a given building, steel would rate poorly for water consumption and pollution, concrete for high embodied energy and low recyclability, etc. And let's not forget the function of a thermal mass strategy (most useful in a climate without too much temperature variation). You basically have to prioritize materials based on construction needs and what impacts you want to reduce, and then figure out how to make your material selection GREENER.

You need to make addresses less than 60 characters long so I can send them with little hassle.

What most people don't know is that today's cement plants are usually doubling as incinerators.

Many cement plants burn used tires, medical waste, municipal waste, hazardous and toxic waste -- and call this dangerous practice "recycling."

So when the cement industry says that its products are created with "recycled" materials, they like to mention fly ash and slag -- but conveniently leave out the rest.

Cement kilns are not designed for incineration. They occasionally reach temperatures which in theory might "safely" combust some of what they burn... But kiln temperatures fluctuate wildly, and kilns are subject to serious "upsets" -- during which temperatures drop, and massive quantities of HAPs are emitted.

On top of that, cement plant environmental compliance and enforcement is pretty weak in the U.S., and worse elsewhere. They pay fines as if paying parking tickets, and get away with much more than commercial incinerators.

The industry has an unusually robustly-funded greenwashing arm, so reporters should take claims of "cement sustainability" with a major grain of salt.

One other note... A major pet peeve of mine is opening up some shelter magazine featuring "Green Homes" -- which 8 out of 10 times are built from concrete. The awareness of the hazards of this material is extremely low, so good for TH for trying to raise it.

Some links to groups like Downwinders at Risk in Texas and others in the U.K. would be useful.

And a final comment... The comments here ignore another major impact of overusing cement -- the harm done by mining.

Coal is the main fuel used in the industry (gas plants are possible, but rare). In addition to the harm done to communities and ecosystems by coal mining, you also have the massive quarrying necessary for the main ingredient of cement, limestone.

A single cement plant can require a quary of thousands of acres, as well as landfills for whatever waste is captured in the production process.

Limestone is full of nasty stuff, including many volatile organic compounds, including sulfur. Combine these with the pollutants related to coal-burning, and you get a ton of CO, SO2, as well as mercury, arsenic, and lead from the process.

Those who laud cement as a "wonderful" material are thinking only of their own aesthetic aims, and ignoring the global and local harm done by this industry.

Concrete can never be a "green material" as its unsustainable to manufacturer. Cement requires heavy mining and vast amounts of energy to produce.
Its a wonderful substance to create beautiful buildings with and some are labeled as green buildings. But in accepting this, is ignoring the facts that the material produces more C02 than any other material and therefore is more devastating to the environment.
So yeah, concrete buildings are "green" as long as you forget that we have a delicate biological environment existing outside called the Earth.