Blog Post

The Mismeasure of Buildings: Five Reasons Life-Cycle Assessment Will Not Give Us Zero-Impact Design

Whole-building LCA is about to get really big in LEED and elsewhere. It's a great tool, as long as you understand its limitations.

As part of its "Journey to Deep Green," international construction firm Skanska is tracking embodied carbon of the core-and-shell projects it builds for its real estate development arm. Rather than relying only on available LCA data, which are just estimates and averages, the group is tracking actual transportation miles of both materials and workers, measuring the amount of energy used for onsite equipment and lighting, and carefully calculating total waste generation and waste transport. That level of detail is not found in a typical LCA, and gathering the data is a lot of work. Photo Credit: Skanska Commercial Development

Are you designing the world’s greenest building?

If so, have your model line up here with all the others that have laid claim to the title. That’s right: single-family homes to the left, everyone else to the right. Today we’re finally going to settle this!

As soon as the bell sounds, start entering all your building’s materials into this hand-held life-cycle assessment device. I hope you all remembered to bring your carefully tracked site-visit mileage and the spreadsheets showing carbon released from the soil during construction? Also your energy models and decommissioning plans? GO!

And the winner is…

OK, OK, this would never work: buildings are complex, and there are just too many variables and unknowns. Also, you could never fit all the “world’s greenest” building designs into one room.

Yet to hear some people talk about the hottest new sustainable design trend—life-cycle assessment, or LCA—you would think it was the one and only methodology we need to determine whether a building product or a whole building is sustainable.


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That’s ridiculous, and we explore why—along with what LCA does really well—in this month’s EBN feature article, “Whole-Building Life-Cycle Assessment: Taking the Measure of a Green Building.”

Below are five things to keep in mind when using LCA in your practice.

1. There’s more to life than carbon

Carbon is obviously one of the most pressing concerns of our time, and that’s driving many project teams to think really creatively about how they design. Building with wood radically reduces the initial carbon impact of a building, and we’re seeing a trend toward heavy-timber commercial construction based on results from whole-building LCA.

LCA isn’t so good at telling us, though, about the human-health effects of our materials (along with lots of other important metrics). Most heavy-timber glulams contain phenol-formaldehyde-based binders—which could give some design teams pause, given the amount of timber used and the fact that beams are typically exposed on the interior.

Another problem: although wood has had a long and respectable life as a structural material, we don’t know much yet about the durability of glulam timbers in airtight, high-performance buildings.

None of this is necessarily a deal-breaker, but it’s important to keep in mind that all decisions come with tradeoffs, even if you use LCA.

2. The Rumsfeld uncertainty principle

Former Secretary of Defense Donald Rumsfeld got a lot of ribbing for his statement about known knowns, known unknowns, and unknown unknowns. But the guy had a point.

The data behind LCAs is full of unknowns. We know exactly what some of those unknowns are: a lot of products and materials are just plain missing from our databases. But there are also holes in the data we have, and it may not be obvious what they are. Don’t lean too hard on those numbers; they might fall apart.

3. An ass of you and me

The foremost software tool in the U.S. for conducting a whole-building life-cycle assessment, or LCA, is called the Athena Impact Estimator. Not the impact X-Acto knife.

LCA isn’t like indoor VOC emissions, says lead LCA expert Wayne Trusty, past president of the Athena Sustainable Materials Institute. “You can’t take it in a lab and test it. It’s always about assumptions, projections, and estimates. That isn’t a reason to abandon it.”

Yes, it has a "nutrition" label. No, I would not like to see it.

Of course not—but it is a reason to define what your own assumptions are from the outset and to understand the assumptions behind any product LCAs you consult.

It’s also a reason not to let your marketing department send out press releases announcing your building is carbon-neutral or zero-impact. LCA simply doesn’t have the precision to determine that.

4. Twinkie earns nutrition label!

Here at BuildingGreen, we’re starting to see a lot more press releases about products “earning” environmental product declarations, or EPDs, the short-form report based on a product LCA. That’s like saying a Twinkie “earned” a nutrition label.

You don’t earn an EPD: you pay for it. (You pay a lot for it.) It doesn’t say a product has low environmental impacts but rather lays out what those impacts are. Don’t take the existence of an EPD to mean that a product is green.

Similarly, don’t take the use of whole-building LCA to mean that a building is green. LCA is a great tool for finding high-impact “hot spots” in the building overall during early design and then exploring systems or assemblies that might reduce the anticipated impacts as details are filled in. It’s not a seal of approval.

5. Blinding us with science

Have you heard about the scientist who used the same dataset to demonstrate opposite conclusions: that walking is better for you than running and that running is better for you than walking?

Advocates of LCA claim it’s more “scientific” than other methods of defining what’s green. For example, recycled content is often a good thing, but recycling is energy- and water-intensive and often involves a lot of trucking. It shouldn’t get a free pass. LCA is supposed to level the playing field so that we can fairly compare different products and materials.

Yes, LCA is science. But science is not the same as certainty: anyone who grew up thinking margarine was health food because it didn't have butter fat in it can attest to that.

As with a medical science, there are a lot of moving parts here: LCA is much more like an energy model than it is like a chemistry experiment. Like energy modeling, LCA is an excellent tool to help you estimate the impacts of your building. But don’t fall into the trap of thinking you’ve built a no-impact building just because your software zeroed out on the bottom line.

There is a danger that the patina of science will allow LCA to be used as a bigger, better style of greenwashing (we may even need to update our popular blog post “Nine Types of Greenwashing” to include “Blinding you with science”).

Use it responsibly

This kind of stuff is par for the course coming from product manufacturers, but we hope design firms won’t fall into the same habit. LCA is a powerful design tool but a terrible marketing device.

Read the article to learn more about how cutting-edge project teams are using LCA—and why even the world's foremost LCA experts advise caution.

Published April 26, 2013

(2013, April 26). The Mismeasure of Buildings: Five Reasons Life-Cycle Assessment Will Not Give Us Zero-Impact Design. Retrieved from

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May 15, 2013 - 6:42 am

Great article however I think a more appropriate title might have been "LCA alone wont give us a zero impact building but without it you've got no chance".

Whole of building LCA provides plenty of counter intuitive results and results that really challenge some peoples way of thinking. This is one of the major reasons there is resistance to embracing it as a good tool for informing the design process. Can anyone tell me how else you would go about understanding all of the impacts of a building and work out how to make them zero? I think if we just called it "cradle to cradle" most of the anti LCA people would be much happier for some reason.

Yes it's not definitive and should only be used as a comparative design tool to help inform the process. It is better to be vaguely right than precisely wrong.

Take for instance a building in Seattle (the origin of some great low carbon designs). The carbon intensity of the electricity network is really low due to being approximately 88% hydro and about 6.5% nuclear and only 2.5% coal. So where an average building might have 20% in embodied carbon impacts you can more than triple it for one in Seattle. Without doing a proper LCA you would never know this and go making very expensive operational energy based design decisions that would have minimal carbon savings (if carbon is what you are targeting and LCA can do much more than carbon as alread discussed).

So no it's definitely not a diversion from the real issue - it is the real issue. A good LCA should start by understanding where the big impacts are and working out how to deal with them first. In many cases this might be the operational energy and an LCA will tell you what parts of the operational energy need attention rather than blindly charging off into small design elements because a checklist told you to. 

One thing that was missing from the article is a discussion on "functional units". This is where LCA is at it's most powerful. It allows you to compare two different buildings or different design options on a level playing field. The biggest positive impacts you will often have on an LCA outcome will be in the planning stage where you can maximise the design life of the building and maximise the functionality (more people living or working in a smaller footprint). You might get the full "star" rating with the best thermal performance but if there is only one person in the building and it only lasts 20years it's not sustainable. Functional units like kgCO2e/occupant/year are the best way to remove "green washing" and enable good design decisions to be made.

Our goal was to produce a tool that enabled LCA to be accessible (functionally and economically) from residential buildings upwards. If you're wondering if you should spend $200,000 on the standard building or $250,000 on the "low impact" one  the LCA should provide the answer in less than 1% of the capital outlay for the "sustainable" design features. Money well spent.

We really encourage the active critical analysis of LCA (you don't get into LCA unless you are over critical and analytical!) as it is what drives our industry to improve and become more accurate and reliable. "Green washing" was one of the primary reasons we decided to create an LCA tool for buildings!

Arming less informed people in the building industry with reasons to not embrace it as a design tool is not helpful. We are not asking for LCA to be the definitive process rather that it just be used as another cog in the wheel to getting a good design outcome. The nice thing is that we are seeing more and more individuals and organisations embracing it and achieving some really good design outcomes. Not only that we are finding once they have built it and moved in the actual performance is hitting the design target.

Go LCA ;)

May 8, 2013 - 12:10 pm

I'm no expert in LCA and am working through some analysis for the first time.  Are there any guidelines on the project size for conducting LCA?  What's the typical cost of doing LCA on a building verses what further renewable energy system or energy efficiency system could have been implemented for that cost?  Is there any scientific analysis that an LCA driven design verses a non LCA approach results in a better LCA building/dollar than other design approaches? 

April 30, 2013 - 5:45 pm

Paula thanks for the article - it's good to see LCA discussed in green building publications.  I did want to make a comment to say that anyone who has done an LCA knows all about its limitations - (1) it's a snapshot in time, (2) a lot the data is estimated rather than measured, (3) there are always data gaps and (4) how you model the data can drive the results of the analysis.  However, these limitations don't mean that LCA isn't a valuable tool. LEED has many limitations as well, but it's still better than the alternative of conventional design.  If you do LCA correctly, you can identify environmental 'hotspots' in the value chain, that you might not have identified otherwise.  This makes it useful in separating the 'sexy' environmental solutions from the ones that have a real, positive environmental impact. 

One last point - I realize that 'carbon' is a popular topic, but in order for an LCA to be complaint with the ISO standards, it actually has to look at more than CO2 emissions.  In fact, an LCA should look not at the net emission but apply impact assessment methods that allow the user to get at the potential impacts of the value chain - from ozone depletion to water quality to human toxicity.  The importance of this is that LCA helps the user understand the environmental 'tradeoffs' of different options.  A biobased product may seem inherently better that petroleum based one on a CO2 basis, but the biobased version may generate higher water quality problems or may require more toxic chemicals to manufacture, which need to be taken into account.

No one who has done LCA for a period of time feels that LCA is the only solution to identifying 'green' products or designs. But most of us do feel its an essential tool to examine and prevent a lot of the 'greenwashing' you mention at the end of your article.

May 1, 2013 - 9:23 am

Thanks, Brian! The more we hear from LCA experts on this, the less likely we are to end up in a really bad place where LCA and EPDs are used for ultra-greenwashing instead of for the powerful internal analysis it's intended to be. And a good reminder about the ISO standards! Much appreciated.

April 30, 2013 - 12:32 pm

SCS published an Environmental Building Declaration for the Inland Empire Transportation Management Center.  The EBD did not address carbon emissions as related to construction vs operations (except for commute), but we do know what the kg CO2 equivalent is for the LEED building as opposed to conventional construction.  The EPD noted that a percentage of materilas would be recycled at the end of life which I think would be a benefit from an embosied energy perspective.   

April 30, 2013 - 1:12 pm

Bruce, thanks for the heads-up. I haven't had a chance to look at it, but that EBD is available for download:

April 29, 2013 - 1:51 pm

No, I'm saying that total carbon emissions are about 20% greater than just emissions from building energy use alone, when an LCA of embodied carbon is made and emissions from that source are spread out over an estimated life of the building. Obviously there is an estimate of building lifetime that is arbitrary, but whether it's estimated at 60 or 80 years isn't going to make a huge difference in the total carbon emissions since most come from operational energy use. And all these considerations are dwarfed in situations where the majority of occupants use single-occupant autos for commuting to/from work, as EBN demonstrated, as I recall, in an article in 2007.

April 29, 2013 - 2:27 pm

Gotcha. You are saying that operational carbon is more important than embodied carbon.

I'd agree with that, but that doesn't mean embodied carbon is unimportant. By that same logic, the operational energy of the building is unimportant because transportation energy of workers is greater (30% greater, as our feature article on transportation energy intensity estimated).

Also, if the building life is ultimately only 10 years instead of 60 or 80, that does make a huge difference in the importance of embodied carbon. And, as Frances Yang at Arup pointed out to me, the importance of embodied carbon increases dramatically if you include renovations and refurbishing. That impact is shown on one of the charts we've included in the feature article, if you get a chance to read it. Just another example of why assumptions matter and why communicating LCA results is so tricky.

April 29, 2013 - 1:35 pm

I didn't say that LCA increases carbon emissions. I have read a Swiss study in a professional journal analyzing in depth the carbon of a research building, "Forum Chriesbach" in Duebendorf, Switzerland, that shows that embodied carbon adds about 20% to the energy use of even a well designed building, what the Germans and Swiss call "Gray Energy." The study is quoted in my new book, The World's Greenest Buildings: Promise vs Performance in Sustainable Design, in the case study for this project. As far as I know this study is one of the very few in-depth analyses of total carbon in a high-performance building that has appeared in a respected professional journal.

April 29, 2013 - 1:44 pm

Are you saying that more embodied carbon in the building tends to lead to emitting greater operational carbon? Seems like you'd need to have some faith in LCA to come to that conclusion, but it's certainly an interesting one. How do they account for it?

And we certainly agree on the need for tracking operational energy.

April 29, 2013 - 1:16 pm

As usual, you guys nailed it! There is more to life than carbon and LCA doesn't really provide gain for the pain it inflicts. Moving from unwarranted assumptions to predetermined conclusions is the fundamental problem. Let's just say that full life-cycle analysis adds about 20% to the carbon emissions of buildings (Swiss studies show that) and move on to measuring building performance and improving the design of cities.

April 29, 2013 - 1:30 pm

Jerry, thanks for your comment. Our research actually suggests—anecdotally—that LCA, though inexact, helps guide real embodied carbon reductions and shines a light on other impacts as well. I'm not sure we're ready to throw the baby out with the bathwater; we just want to warn people that the methodology has limits.

I've definitely never heard anyone say that LCA actually increases carbon emissions. Do you have a link to that study? Thanks again.