Embodied energy calculations

If you are curious about the calculations that went into the embodied energy estimate, this spreadsheet contain all the numbers your heart desires: Embodied Energy Calculation.

This is not a polished document. It is the working spreadsheet into which I put all of my calculations on the embodied energy of the house. The first sheet is the house broken down by material or system with the calculation of the total embodied energy for that material. These calcs reference the materials sheet (the third worksheet in the document) and should be fairly understandable. These are all done in kWh rather than the building industry’s standard of BTUs, but coming from the alternative transportation industry, kWh is a number I have a “feel” for.  It can be easily converted to BTUs if that is the way you think (1 kWh = 3413 BTU).

The bottom of the first sheet includes calculations for how much volume of each material is in the house. Many of these formulas are simply long additive lists because they are taken directly from the house plans or on-site measurements. These will be peculiar to the design of our house, and should you be so crazy as to want to analyze an alternate structure with this method, you would need to spend most of your time generating these numbers that would be particular to your structure. You will notice lots of 1.25 fudge factors to account for offcuts, waste, and simple systemic undercounting that tends to happen in a “bottoms up” estimate like this.  Where I use a fudge factor I try to indicate the rationale in a note.

The second sheet is operating energy calculations. It has a lot more than just the operating energy of the house. It also has the paper towel calculations and my flying and other energy use for the year. It has all the numbers you would need to figure out, for example, how far it is OK to drive your car to a farmer’s market for local produce before the trip adds more food miles energy to your food than your local market where all the fruit comes from Chile. (Not that far unless you buy a LOT of produce! Luckily, our farmers’ market is in bicycling distance.) This is also the sheet where you can find the tool to calculate your personal flying energy (yikes!) and has some conversions for using lbs of carbon as your “common currency” for comparisons. It should be said, though, that conversions aren’t necessarily simple multiplication if the energy in your summation comes from sources with widely varying carbon production per kWh. All my calcs get done with Northern California conversion factors, but if your energy comes from coal or hydro or solar, you’ll get very different numbers. If you want to calculate your carbon footprint, there are many better web based calculators out there that are pretty simple to use.

The third sheet is the individual material embodied energy values with a long list of the websites where these numbers were harvested.   The embodied energy of a “raw” material like stone or sand is very location dependent as it is minimally processed, so the shipping costs predominate. Highly processed materials like aluminum or paints or laminated plastics are much less location dependent as the processing energy put into them dwarfs the energy of transportation.  Luckily for the accuracy of the calculations, the low EE materials with the greatest regional variability in their value, are a relatively small portion of the overall EE, and the error generated by using an average value is small compared to the inaccuracies associated with things like estimating how many steel fasteners are in a structure.  (I actually went and counted the hangers and fasteners in typical studs, joists and trusses in the house to make a reasonable estimate, and I could only do that because there was no drywall up yet!)

This whole thing has many sources for error, so small differences between two choices should not be considered significant. What I was really looking for was where materials choices made unexpectedly large or small differences in the overall embodied energy of the house. Without adding it all up, it would have been impossible to really understand the repercussions (or lack thereof) of each choice.

If you find any errors, please do let me know – I will continue to refine the spreadsheet and post corrected versions if any fundamental errors are found.

19 replies
  1. Stephen Feber
    Stephen Feber says:

    Catherine we met @ TED and talked @ Wokcano. Great talking with you and a great website for your house project. The s/s is really interesting. Thank you. As an aside – according to my calcs your house consumes about twice the energy of the highest standard Passiv Haus which is 15Kwh per square metre per year. Correct? If you send me an email I’ll send some pics of the zero carbon project we’re doing in the UK.

    Best wishes


  2. Steve Mouzon
    Steve Mouzon says:

    Fascinating site, Catherine! I was turned on to it by your TED talk. I completely agree that we’re often missing the big picture. In that regard, please consider this post. This post makes the case that lovability matters to an even greater degree. Namely, if buildings have to be torn down every 40 years on average, then in 200 years, a lovable building that doesn’t have to be demolished is twice as good as LEED buildings (average of Certified, Silver, Gold, and Platinum, according to USGBC data.) With that having been said, good luck with the completion of your home! Also, when you get a chance (probably after you’re moved in,) take a look at the rest of the Original Green principles.



    • admin
      admin says:

      Hey Steve — thanks for the comment. I think I’ve fixed the links. If you get a chance to check them, let me know if they’re pointing where you intended.

      -Paul (Catherine’s husband)

  3. Steve Mouzon
    Steve Mouzon says:

    Catherine, I was trying to embed two links in the previous post and it didn’t do what I expected. Instead of clogging your inbox with repeated attempts to get it just right, please feel free to delete the second link if you like… assuming that you see fit to post the comment, of course… thanks!


  4. salmanff
    salmanff says:

    I loved your tedtalk, and I am a big fan of calculating “embodied carbon.”
    Have you thought about a “Carbon Added Tax”, from a policy perspective? Obviously there are a lot of arguments against – eg “it’s too hard to calculate” – but I don’t think people have really considered the full advantages of creating such a tax on embodied carbon. Here is my (somewhat outdated but still relevant) argument for the Carbon Added Tax: http://salmanff.blogspot.com/2008/12/case-for-cats.html
    I’d be delighted to chat if you want to discuss.

  5. Curtisknc
    Curtisknc says:

    I too found you through Ted.com. That is one dangerous site!

    Very intersting Ted chat, Blog & worksheet.
    I am working on some renovation vs new construction cost numbers myself.

    A couple of questions:
    Was the Renovation Cost in kWh asssuming a 2600 sf resulting structure?
    Have you considered your payback numbers in light of the emobdied energy from the house that went to the dump and the resulting release of carbon through it’s decay?

  6. Catherine Mohr
    Catherine Mohr says:

    To Steve Mouzon: I agree that if you can preserve and maintain a sound existing structure, and make it sufficiently energy efficient, then you will come out ahead over new building – ESPECIALLY if the alternative is making ugly energy efficient buildings that you tear down every 40 years. Even with our best efforts, and paying a lot of attention to detail, our payback in energy (NOT money!) is still decades over if we had renovated the existing structure. I like to think, however, that we were taking an extremely unloveable existing structure, demolishing it, and putting in it’s place something that some day will be considered for historic preservation well after the house has been around for over 200 years. The key to all of this is to build with a plan for long term maintenance, and to build with a quality that will last

  7. Catherine Mohr
    Catherine Mohr says:

    To salmanff: the carbon added tax is an interesting idea – the thing that boggles my mind is trying to figure out how to optimize on all of the things that matter – carbon, water, air quality, human rights, biodiversity… there are so many, and they aren’t all measured on the same scale, or even optimizeable at the same time.

    To curtisknc: the calculation was just upgrading the existing 1400 sq ft structure without adding any square footage: i.e. no library, and most of my books would have still been in storage. I didn’t try to calculate the additional CO2 in the wood that wasn’t salvaged (it was the only thing in the debris that had any real decay potential, the rest is things like broken tile and gypsum board which will be around for millennia), so that would have added a bit, but not a huge amount compared to carbon produced by the energy to process it. Similarly, I didn’t take credit for the carbon sequestered in the wood that went into building the new house.

  8. salmanff
    salmanff says:

    Hi Catherine,
    Thanks for your message. I imagine how difficult it must have been for you to take into account of all those factors when making your decision – dilemmas few other people would dare consider.
    But I think that putting a fair price on these factors provides a path for addressing the dilemma, assuming that it would be possible to measure them and put a FAIR on them. If each of these factors did have a fair price (like a tax based on their detrimental impact) then each purchase decision could be made much more easily. You could compare two products and understand their total impact, using the common benchmark of $$. Or you could weight the price of each factor in your own conscience, and be able to make better decisions without going through the torture of doing the calculations yourself.
    Of course, that begs the question of how difficult it would be to measure these factors correctly, comparably, and at a reasonable cost… and to put a fair price on them. Clearly, it is quasi impossible to measure and put a price on something like “human rights.” But carbon has some advantages in this respect: Not only is it measurable (ie by grams) but it is also uniform globally. (ie A ton of carbon emitted in California has the same impact on global warming as one emitted in the Amazon.) This makes the CAT very attractive, because it means that even if only a state like California imposes such a tax, it would have global implications. The CAT takes into account the carbon emitted throughout the whole supply chain, out to the far reaches of the world. So, a factory in China or Vietnam selling products that end up in California would be indirectly incentivized to take their embodied carbon into account. A locally regulated CAT leverages the supply chain to affect emissions globally.
    Of course, there are many other questions to answer: Who decides on how we would measure the carbon impact of each product? How do you deal with transaction costs for small producers? .. and with the inevitably imperfect information on emissions?
    On the other had, if we don’t have answers to these questions, how on earth would any other solution to carbon emissions be effective? It seems to me that every other “solution” tries to resolve very large issues by glossing over such important questions, so even if the CAT is a terrible solution, it may be the best alternative.
    And as far as carbon is concerned, I think there is a path to answering some of these questions. With water, it is harder (since it is inevitably more local) but can be envisaged… Other factors are much harder to quantify…
    Finding a way to know and price the embodied carbon of all products and services is no panacea for solving the dilemma you pointed to, but it might just provide a good starting point.
    thanks for listening.

  9. wboyer3635
    wboyer3635 says:

    Catherine, I agree with Steve M. // Different subject: Could you change this website to include a facebook link? That’s one way to get the word out. I forgot where I saw the TED video, but they probably dont use FB links either. It’s my reflect response: [1] i see something that looks 100% credible and vitally important. Then [2] “Where’s the FB link? I gotta tell several folks and maybe post on my wall. ”

    But alas, without the link I can only copy a URL. It takes more “embodied energy”! – to copy-paste to text file, login to FB, start a wall posting, then copy-paste the URL. Where as the FB link lets me write a fast blurb from off your website.

    • Paul
      Paul says:

      wboyer — thanks for the good suggestion. I have added an “add to facebook” link at the bottom of the page. If I get a chance, I may move it up by the RSS subscription link.


  10. yannick
    yannick says:

    Hi Catherine, also saw you in TED video.

    I’m a developer constructor in Brazil and I’m always looking for new ideas to implement in the houses we build for social housing.

    I’m also a geek, so I went ahead and tried to organize and ‘clean’ your sheet (light yellow are inputs, red are numbers i didn’t know what to do with and green is automatic to show interesting ecological results) and put your spreadsheet in google docs.


    If you’re ok with it i’ll leave it there and of course when you give me an email address provide you the editing and ownership rights. this way you never have to upload versions and you can have others contribute.

    These numbers are important for me as I help my team quantify for both customers and investors why its good to think green…We also need to compute also the actual extra cost if any of including such ‘innovative’ practices…you wouldn’t happen to have calculated that too?

    In the mean time I’ve asked my team to research some of the products here in Brazil.

    Thank you for your short and sweet presentation at TED.


  11. Katiekross
    Katiekross says:

    Thank you for the great TED talk and site! I recently built a green house myself and wrestled with environmental tradeoffs, costs, and lack of reliable data to make informed decisions about big questions.

    A question for you about your embodied energy calculation (and my apologies if I’m misunderstanding the talk and spreadsheet). Why isn’t the embodied energy of your new house ADDITIVE to the embodied energy of the older house you demolished, less the salvaged materials? Let’s say that even if you recycled some materials, you sent some scrap material to the landfill; its embodied energy hasn’t gone away. Energy was still used to make that material that was part of your house which is now sitting in the landfill. So, wouldn’t the more accurate comparison be Embodied Energy of Old House (less recycled/repurposed materials) PLUS Embodied Energy of New House materials, as compared to embodied energy of a new house built ground-up on a greenfields site?

    Just wondering…

  12. dcoylewhite
    dcoylewhite says:

    i’m curious – have you checked out the Athena Institute analysis tool for this type of calc? looks more reliable for north american work, but i haven’t tried it yet so i’m curious to know if you have perused it.

  13. pchin
    pchin says:

    Hi Paul and Catherine –

    This is Paul Chin – an old Aerovironment alum. I came discovered the TED talk surfing the internet. Which in turn, lead me to this site. Awesome that you are sharing so much with the world. Paul MacCready would be proud of what you two have done. If you have time, contact me.


Trackbacks & Pingbacks

  1. […] costs, but by being mindful of embodied energy, she and her husband cut that figure to 150 MWh.  Her accounting uses figures from the house’s architectural plans to determine the material inputs for the […]

  2. […] For all the data she refers to in the video, there is a blog at http://www.301monroe.com which includes her spreadsheet in this entry. […]

  3. […] gas vs. hydro vs. nuclear). Fortunately, after reading through her posts I came across the one that explains how she did her EE calculations, as well as attaching her Excel spreadsheet with the calculations. She also did another spreadsheet […]

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