Life Cycle Assessment for beginners

Life Cycle Assessment (LCA) is a tool that is slowly gaining popularity in the study of the environmental impacts of products. In buildings, it's use is still sparse and not always consistent. However, I came across a few products that are fairly useful in exploring how an LCA study works, its different parts, the lingo...Image via Wikipedia

First up, Sustainable Minds is an online based tool that allows you to fairly easily create an LCA of a product, say a shipping container. The tool walks you through the necessary steps to set up a baseline case and then explore alternate designs. The approach taken boils down the LCA indicators to a single score called the Okala points. A free one month trial is offered and academic pricing is available. They have also begun offering weekly webinars. If you are a designer of products, even building products, this may be a good tool if you are interested in quantifying the environmental impact of your design.

Second up, is perhaps its main competitor Greenfly. This tool is somewhat similar, although perhaps it is even more friendlier to use as it guides the user with useful tips along the way to reduce the environmental impact. The tool was created in Australia, and it is free. Well, it's free for now. It seems that they are offering a free trial until they work out all the bugs.

Finally, there is the LCA Calculator which is set up as a list of drop down menus and such. It is perhaps most useful for a quick comparison of design alternatives, but not as refined as the previous two tools. Nonetheless, it is available for free.

So there you go. If you are a designer of any kind, you have probably felt the urge to justify how green your design is. These tools can help you 1) become familiar with LCA methodology and 2) calculate numbers to substantiate your "green" claims. Be sure to check these LCA tools out and keep an eye for new ones!

Watergy

Image by Argonne National Laboratory via Flickr

I recently came across this free spreadsheet tool (and pdf manual) called Watergy when navigating the Federal Energy Management Program website. Since I love to see numbers I had to share it here. More interestingly, it is always useful to see behind the scenes how these tools work to make estimates that can inform decisions.

Be sure to check this tool out if you are interested in understanding the energy and water use relationship that exists in the operation of buildings. Basically, water savings in places like faucets, sinks and showers can lead to reduced energy use since less water needs to be heated and less energy is required to convey it and treat it. Some places like islands use even more energy because their potable water is usually sourced from desalination plants which use a lot of energy.

CoV Pecha-Kucha Green Buildings

Image via Wikipedia

I will now take this opportunity to give my two cents regarding Vancouver's attempt to be the Greenest City by 2020, particularly after watching David Ramslie's talk at the Pecha-Kucha event.

First, I found Mr. Ramslie's vision to be very innovative and one of the more enjoyable ones at the event. I had never heard about the analogy of the transition we are living in the green building movement to the idea of computers being transformed by the internet. I am confident he is right: the future of green buildings will be regional based and heavily aided by buildings communicating with each other.

Image via Wikipedia

However, as much as we like to hear the statement that Vancouver has the greenest building code in North America, I have my doubts. In fact, I would have appreciated if the speakers had stated exactly why they say this is so. If we are talking about promoting LEED buildings, then yes, Vancouver is doing plenty, but there are still some things that must change if Vancouver will be the greenest city.

Vancouver should not be a island of green in a sea of sprawl. Therefore, Vancouver must get its suburbs on board ASAP, North Vancouver, Surrey, Burnaby, ... It is assumed from the wording of the city vision that a "one planet footprint" is being used as a measuring stick. If so, I assume that they are talking about the Ecological Footprint tool, and we must begin to discuss the strengths and weaknesses of this assessment tool. Being a "one planet footprint" city is hard for a port city that imports resources from all over the world.

The problem of housing affordability needs to be addressed and discussed. The city keeps saying that the more condos that spring up, the lower rents should theoretically be. By now, we understand that this is not working. Bing Thom Architects has published articles calling for more family friendly buildings (i.e. less one bedroom and studios). If we want Vancouver to be green, we need to retain people here and have them build a life they can afford.

We also know the benefits of mixed-use buildings but what policies are in effect to promote this, particularly in retrofit situations? What is the laneway housing equivalent for promoting mixed use livability and not mere densification?

New funding mechanisms should be developed to support lowest life cycle costs which often have a higher initial cost. Developers are here to make money, and with the exception of a handful, don't care about making their buildings energy efficient. They will cut corners because they know people will buy and be fooled by the fancy looking but poorly built residences they purchase. This is something that has to be mandated through policy, and this is why other neighboring cities must be in the loop, so that the whole region can truly prosper.

Overall, we need life cycle thinking in how the built environment is managed. Reduced energy use during building operation is very important, but it is not everything. The regional aspects are more important. Green buildings alone won't do it. We need community building, neighborhood flourishing and citizen empowerment.

Image via Wikipedia

I feel that the city is taking a lot of reasonably good decisions (perhaps even bold) in the right direction, but it will take more to reach the targets the city has set. If we are living responsibly, I think the processed satellite image shown will look more green and less like a purplish virulent disease.

Nonetheless, the fact that we are talking about our city for the next couple of decades is amazing and encouraging in a world where politicians are primarily worried about the next election.

Remember to keep an eye on the city's public forum where people are posting and voting for their favorite ideas on how to reach Vancouver's goal.

Ubuntu 10.04 LTS

Continuing with the topic of productivity tools, I have recently installed Ubuntu 10.04 LTS on an old computer I was considering trashing soon (not anymore). In case you are not familiar, Ubuntu is a free and the most popular distribution of the Linux operating system (a Microsoft Windows replacement essentially). However, if you ask them they will tell you that Ubuntu is much more than this, because on top of that, they have community.

I actually used to work a little in Ubuntu back in the day when I worked as a web designer, and although I liked it, I wouldn't have considered switching over entirely. I recall pdfs would sometimes look very different (font and transparency issues?), flash on webpages did not usually work properly and things like mp3s would not work without some sort of guru Linux expertise in using their obscure Terminal (which used to be also needed to set up your internet).

But the software has come a long ways since then. I was extremely surprised to find how easy it was to install, although I did have to do a few work arounds to get it going. All the issues I had previously mentioned from my past experiences were no longer existent. Ubuntu fulfills pretty much 95% of my needs. This leads me to believe that this latest release and perhaps the following (scheduled for 10/10/2010) are pretty much the tipping point to have a growing mass of Ubuntu users.

• Free!
• Super fast (note that this is an old computer that took like five minutes to boot up Windows XP)
  
• Stable! (Ok, it does rarely crash, but hey it boots up so fast it's not an issue)
  
• You can update ALL your software in one click!
• No antiviruses/malware scanners!
  

The only thing that is in my opinion an absolute requirement is that the computer you are planning to use has an internet connection. This is how I downloaded things like Dropbox and drivers to use my Lexmark all in one printer/scanner.

From an academic engineering perspective, there are a number of things that are still missing. There are a couple of FEA programs, but other than that very little. The engineering software repository doesn't have much for the Engineering category. Below I list some software that I thinkI have found useful and hope you will comment if you know of other software.

• Scilab - The Mathwork's Matlab open-source equivalent developed in Europe. Commands and certain tools are different, but essentially you can still perform a ton of operations on large matrices, programming. Other useful things like programming and reading csv or xls files are also supported. The fancy interface and report generation from Matlab is unfortunately not available, yet.
  
• Wine - The gateway program will let you install and run software meant for Windows. I have yet to experiment with this one since most of the Building Information Modeling software, LCA software (Athena, Simapro), Autodesk Revit, AutoCAD, Robot, RISA, eTabs and the list goes on.

So to summarize, I think in a couple of years there is likely to be a mass transition of users that use primarily Ubuntu. As this happens, more and more software will be available until Wine is no longer needed, and at last we won't have to waste time, energy and resources on "protecting" our computers from viruses, malware and whatnot. If you know programmers, tell them to start writing in stuff like Qt, because the future is full of operating system options, and those most successful will let their software flourish in multiple platforms or online (like Google).

Life is busy, productivity tools

Life is busy and green buildings are not as green as they seem. The summer in Vancouver is finally full of sunshine, and life is hectic, but I have recently found a couple of tools that are keeping me on track. I do not receive any money from promoting these but I did want to share in case anyone out there is interested.

Tag2Find

This tool should be a part of the Windows operating system. Basically, if you use Google Mail you are likely to be familiar with tags. They are like the next generation of folders. As we all know, categorizing files to find them later can be problematic. I have a ton of pdfs, some are dissertations, journal articles, power point presentations, and it is very hard to create a folder structure. Tags are the answer to this problem. This software is free, and I have found it so useful to help me organize and keep track of my files. Anyways, take a look if you think this might help you.

Dropbox

Dropbox is another tool that is so essential. Basically, the free service offers you a couple of gigs for storing your files. By downloading and installing the software, you are able to synchronize files along your computers through your Dropbox folder. It is like an online folder, so that if you are working at home, at work, with your other laptop, you can have easy convenient access to your files. The files are kept synchronized with no work from your part. Also, this stores my thesis document which doubles up as a secure backup location for me. If you pay, you can actually get more space.

That's it for now! Time to go to the community garden. Hope you all find these tools as helpful as I have.

Pecha Kucha Vancouver

This event took place a few weeks back. Although I did not attend, I was surprised to discover that the talks have been posted online. The one I'd like to share today by David Ramslie on green buildings. I will offer some commentary in the next few days. What do you think?

Demand vs. Supply

The energy crisis issue in North America has been framed as a problem of supply of energy. So a lot of the discussion is on what kinds of energy plants to build and who is going to make more money. However, the issue of demand is rarely heard, which is why I was very happy to read the following article from Green Building Advisor

How to Solve the Energy Puzzle

Stop worrying about clean and dirty power; focus on your thermostat

Posted on Jun 21 by Carl Seville, GBA Advisor

Energy solutions are right at your finger tips We need to learn how to turn off our HVAC systems and be comfortable in a wider temperature range.

The disastrous oil spill in the Gulf of Mexico has generated endless news stories and opinion pieces on the state of our energy industry and how to “fix” it. Most of the conversations address two key points: independence from foreign oil and alternative energy. Strategies on the first point tend to be limited to expanding ... READ MORE

TED talk

The following video captures the importance of quantifying energy and the hidden variables that dominate once you begin digging deeper. I believe this really resonates with the message of this blog, although clearly, we must never forget the bigger picture, as energy is not everything. We care about living in healthy spaces that inspire and comfort us, and a lot of this can't be distilled into a simple metric. Enjoy.

Make sure to check out the presenter's blog at: http://www.301monroe.com/

CaGBC National Conference 2010 and defending LEED

So I was able to volunteer at the CaGBC National Conference this year as it was hosted in Vancouver. I found it to be a pleasant experience, although I still enjoyed the Living Future unconference in Seattle this last April.

The theme of the conference was Performance Matters, and it almost seemed as a response to the infamous reports of LEED buliding's energy underperformance that were popular a year or so ago. My general feeling is that LEED is not as bad as most of us would be led to believe.

Sure, the LEED rating systems are far from perfect, and in general there is no way to explain why some points are so much easier to obtain than others, why the radius makes any sense, or why the fact that something is recycled automatically makes it better. However its original purpose was to transform the market, not to be used as a design tool, which is its unfortunate situation today. Additionally, some of the concerns, such the regional characteristics of a project have been addressed to some extent in the latest revision of LEED v3/2009 through the use of regional priority credits, slight increase in some requirements, a lot more points in the Energy category, documentation of energy performance etc.

So LEED is not bad, what is bad is having designers who are LEED accredited professionals (APs) who have a substandard understanding of sustainable building practice. Not to make anyone blush, but there were a few attendees at the conference who were much more interested in checking their emails on their Blackberries and Iphones than in the presentations their employers paid for them to attend.

The truth is that a lot of companies are slow to understand how the green building movement will affect their everyday business in the future. I am guessing that a lot of them are not going to make it. Many of them would be smart to have a little insight into the future of green buildings.

So what is good about LEED?

• Indoor Air Quality: Energy is not everything. In fact, most people may not care too much about how much energy they use, but they do care about their health. As we spend on average 90% of our time indoors, we are usually breathing a lot of toxic stuff as a result of everything that surrounds us, whether it is the adhesives in the carpet, the cleaning products that are used or humidity that has caused mold and spores. LEED takes a stab at addressing this impact which is very relevant in our lives and which may be most important for the elderly and the younger kids.
• Transforming the market: LEED has transformed the market and at least today people have a better understanding of the trade offs and opportunities in green building.
• Productivity gains: Unfortunately very difficult to quantify, but most studies have found a good indication that things promoted in rating systems like LEED: having day lit offices and views improves productivity. Even a small percentage increase in productivity results in an amazing amount of money. In fact, a lot of the people who believe in LEED are not environmentalists but simply people who truly believe that they can make more money by having healthy and happy employees.
• Holistic design: At the very least, LEED is useful in walking people through the important parts of a building's design and delivery as well as pointing out opportunities to improve the quality of their work and the health of the building occupants.
  

So overall, LEED has done much more good to the industry than harm. I anticipate they will get their act together and try to push for more building commissioning and verification of low energy, low water usage and happy occupants. We are all learning to create good buildings, and it is natural to make a few mistakes. Also, we can expect LEED to get better. It has to! Otherwise, GreenGlobes and the Living Challenge are sure to take a big slice of their cake.

Estimating water use during building operations Part 1

Overview
After much anticipation, I would like to treat the topic of quantifying annual water usage during the operation phase of a building. Please note that this procedure is rather similar to the one proposed by LEED and other rating systems, but the assumptions, their variability and validity of such are examined here in more detail. The procedure outlined is thus a predictive tool rather than a relative comparison tool and is thus better fitted for actual-performance oriented rating systems such as the Living Building Challenge or for people who want to understand the variability of their building or home's annual water use.

Surprisingly, I don't hear too much talk about carrying out these types of calculations. It appears most people are focusing on a more practical relative approach such as this post on office water. That post points out how the Building Research Establishment (BRE) in the UK has set a best practice annual water consumption target of 4m³ water per employee (knowing 1 m3 is equivalent to 1,000 liters, this means 4,000 liters).

Please note that this post does start out conceptually, as I believe it is best to understand the whole realistic complexity of a problem if we are to attempt to understand and model it properly. Then we can talk numbers and math which in this case is extremely simple and would make an awesome "green" teaching module in applied math or word problems (you just need to know how to multiply and add).

Procedure
"Real" water use during operation can be somewhat arbitrarily divided into four main sections: water used by occupants inside the building (hygiene purposes like showering, cleaning), water used by occupants to drink, water used in processes (cooling towers, heaters) and water used for landscaping an other uses outside the building. Sadly, an additional use of water is through leaky pipes, something that can happen through the distribution system or in any of the pipes or fixtures inside and around a building.

Also, note that there is a correlation between water use and energy as people for some strange reason refuse to take cold showers and don't like using cold water for washing their hands and cleaning their dishes. This is correlation with energy use is probably a topic deserving attention in a future post.

The basic idea in calculating water use inside a building is to know the number and type of fixtures available in a building. The two general types are those that are flush related, such as toilets, and those that depend on the duration of use such as sinks and faucets. User behavior totally dominates the annual water use. In fact, as can be seen in the simple spreadsheet (at the bottom of this post) that I have put together to illustrate the procedure, the specification of a particular fixture only provides us with one item of information and that is its water demand per use/duration. The rest is all human behavior, proper maintenance and habits. Today, there are more water saving showers available, such as those that allow you to easily reduce or turn off the flow while you are lathering with soap, but you still have to pay a premium for these.

Anyways, I am uploading a simple spreadsheet for flow fixtures so you can investigate yourself. As an example I have entered two showers, the first one based on real data from actual measurements and the second one is how rating systems like LEED would calculate it using more traditional assumptions. You will see that there is a difference per day that is further enhanced when you look at an entire year. The interesting thing is that flow is also variable in these fixtures depending on how much you open or close the valve. Thus behavior is very important for flow fixtures, which is great, because then we can open the valve a little less when we use it and we will be saving a lot of water. The flow issue is different for flush fixtures such as toilets, which will be included in part 2 of this post.

Just in case you were wondering, you can also find out the water demand of your flow fixtures in your home. All you need is a large container, preferably a measuring bowl, so just open the fixture to the level you would normally use it, begin measuring time say 5 seconds and pull out the container. Read the volume gather and divide by the minutes to get your LPM (remember there are 60 seconds in one minute). So, if I applied this procedure to my shower fixture, perhaps I would find that I collected 800 mL in 5 seconds, so 0.8L/(5/60)min= 9.5LPM.

Tracking water

Overview

Tracking water is not easy. Water footprinting is a term used these days to estimate the direct and indirect water consumption associated with a product. As suggested in the previous post, there are important issues with water. The interest is not only the consumption of water associated with something, it is the degree to which the waste water is contaminated, as well as the time element and its role in the natural world (to name a few).

Footprinting confusion

Now, it is important to differentiate the terms water footprinting and carbon footprinting from the "ecological footprint." The latter is a concept coauthored by Bill Rees and Mathis Wackernagel at the University of British Columbia ten or so years ago. The ecological footprint is about collapsing impacts to a common metric of an area of land. Basically, all we consume or produce requires an amount of land to either create what we want, or absorb the waste we don't want. There are limits to the rate at which things are made and the rate and capacity of the discharges we produce. Thus, it is common to go to those websites that give you a quiz and then tell you that if everyone on earth lived like you did, we'd need several planets. I have not studied this ecological footprint concept as I see it as being extremely uncertain since I don't believe we understand the dynamics of regeneration and absorption of land. However, I believe Mathis Wackernagel is advancing some of these issues through the Global Footprint Network.

The point is when people talk about carbon footprinting or water footprinting, you really have to check what they mean by that. Most of them are not referring to the ecological footprint which would have units of an area of land. Instead, they would have units such as kg of CO2 equivalent or liters of water.

Tracking water woes

So what do I see as the shortcomings? (I sound like a pompous academic, but please believe me when I say that this blog is just a compendium of opinions not necessarily shared by anyone else) Well, I think time is very relevant when we speak of water. This is because water is part of a cycle, so in my mind, water used for growing corn, although excessive is preferable to the perhaps smaller amount of water used to wash a concrete truck. Of course, the problem in my argument is that I am looking only at an instant in the entire life cycle of each product. Nonetheless, one could still argue that the time of resource use and discharges is important if we are to predict more accurately real impacts.

Similarly, the quality of waste water is a concern. Here is where my knowledge breaks down as I sincerely don't understand well the chemistry of water pollution. This, in turn, leads to the spatial concern of where the discharges occur, as impacts to wildlife or humans may occur.

Responsible design of buildings for reduced water use

So the primary concerns with water at a building level is to promote responsible use of water. This can be done by attacking the big water demands, such as how much water is required per flush of a toilet. Composting toilets, toilets that use greywater and ultra low flow toilets.

Another important design consideration is to offer submetering that provides immediate and continuous feedback on water use and where it occurs. This is expensive at the moment although I do suspect there must be a low cost way of doing this since all that has to be tracked is the number of uses and length for each fixture. It is really amazing that this is not mandated. If we don't know how much water we use and where, how can we change our behavior to use water more responsibly?

The last design consideration is the cheapest, but perhaps the hardest: to make people conscious of their behavior. We can wash our hands without having the water full blast, it may take a few seconds longer to complete the operation, but we will save water. This doesn't require us to spend any money on technology! Another option I have heard is to stick a brick inside your toilet water reserve provided it does not interfere with the toilet's operation.

Finally, water provides a challenge to designers. On one hand, it can be argued that green roofs are beneficial for a lot of reasons, however, their existence on a building roof, many times complicates the collection of water. The other thing is that ideally, the water collected would be stored near the roof to allow gravity (instead of pumps) to do the water distribution for things like flushing toilets. This imposes a design complication that also compromises the owner's ability to get reasonable insurance since it presents a perceived risk to insurance companies. Also, perhaps most importantly, you don't want to use all the water that falls on your roof, as part of that belongs to the water cycle and should be inflitrated down into the ground. Here the idea would be to design a system that collects what will be needed and then allows extra water to overflow into a conveyance system that allows the water to recharge the aquifer. All this, provided you live in a place that is not a desert, although either way, there are usually dry months, which mean you have to collect additional water when it rains more (thus increasing your collection reserve dimensions). Does anyone out there know of clever designs that help reduce water use?

If you'd like to learn more about water footprinting visit the Water Footprint website.

Also, I hereby promise the next post will have numbers and calculations, because after all that was a primary goal of this blog. I think by doing so we will expose the gaps that exist in our knowledge and our estimates.

Water, buildings and cities

Water is a key element of human survival. So why is it that we haven't made it a priority in our cities? Why is it still illegal in most places to use rainwater or grey water (think used bathroom sink and shower water)?

My understanding of the water issue goes something like this: Water is precious, it forms part of a natural cycle (the water cycle). Although there is an abundance of water in the world, very little of it is potable. The general problem is that we use too much. Things that contribute to this, is the fact that we know very little about the resources used in our buildings. For cars we often want to know what the mpg rating is, but for buildings, do we ever stop to ask what the annual water use (L/year) is or energy use (GJ/year or GJ/year/m^2)? But that is a rant for a future post...

The primary problem in cities, which is increasingly where most of the world lives, is that we have in our infinite engineering wisdom designed cities to take up a lot of room (sprawl), given priority to cars, and in so doing have created a "crust" that deliberately interferes with the water cycle. Water is meant to be held temporarily in the leaves of trees and infiltrated to recharge the aquifer. Some of the water is then released back through plant evapotranspiration and the cycle starts over. Of course nature works rather differently from humans. Nature tries to promote life, while our human solutions don't. This can change!

So, some of the consequences of having all these paved areas are that water speeds up and collects creating flash floods, water is unable to recharge the aquifer, water is unintentionally contaminated with oily car residues and cigarette buds, transferred to a waste water treatment plant where we then use significant amounts of energy to clean it up and then a little more to redistribute it through the use of pumps. This is a problem in my native city, the once prosperous Tenochtitlan, a city surrounded by a lake that now suffers both droughts and floods and is known as Mexico City.

Other bad consequences of paved surfaces are that they contribute to the warming effect of cities, called the urban heat island effect, and they require expensive maintenance which will inevitably disturb you someday when the machines are loudly operating by your front door (and additionally cause you to pay more taxes for what is now called "our aging infrastructure" whereas it could be called "our stupid and short-sighted investment of the past").

OK, so what can we do? Well, we can do better for sure, cause what we are currently doing is wasteful and irresponsible to say the least (we are not securing a bright future for our children). We could use resources better and more consciously. We could design buildings to be sub-metered so that we could understand that our long super-hot showers are perhaps a shameful practice if we claim to be "green" at least giving us the option of making the decision to be wasteful. We could use some rain water and have systems that ensure that we adequately recharge the aquifer. We could plant more trees and have less parking lots.

Similarly, we could begin to try to imitate nature, treat the waste water from our building on site. This is what I believe is the right thing to do, but a lot of this is illegal (depending on where you live) and for a lot of people it means very risky business, so the next thing we have to do is organize and spread the word to help this become legal. We must do research to demonstrate the savings and synergies that exist that will help us reduce our dependence on fossil fuels and live a life that is connected to nature, because nature will then help us heal. Ok, that last part came out a bit spiritual, but it was sincere.

I will conclude this article with a suspicion. I think that overly densified areas are perhaps just as bad as sprawl areas. Is there a balance? I suspect that the balance is NOT more high-rises, specially when we consider other social dimensions of urban life.

LCA and realistically estimating impacts

I have been extremely busy working on my thesis these days, but I suddenly find the need to resume writing, putting my thoughts out there with the hope that people who share these interests will read them and comment.

I have come to realize during this learning process that there are many unanswered questions in the environmental impact assessment of buildings and other elements of the built environment. When I began documenting my literature search, I saw a myriad of approaches, the most scientific (or the ones most cited by other researchers) having a Life Cycle Assessment (LCA) component.

In case you are not familiar with LCA, it is basically a material and flow accounting process that begins with the extraction of raw materials, continues through processing and manufacture, use, maintenance and disposal (end of life being more politically correct as we hope things are reused or recycled), as well as all the transportation links in between. However, it is more than this mere accounting of flows (which would technically be called the Life Cycle Inventory, a step in the whole LCA), and attempts to offer the potential impact. I will always emphasize the word potential, since LCA's greatest weakness, at the moment, is that it does not keep track of time or place of the material and energy flows.

As you can imagine, when we speak of impacts (things like Eutrophication, Global Warming Potential, Smog Formation...) we believe that they are strongly correlated to where and when a relevant discharge occurs. For example, what is the impact of car exhaust in a highway near a forest as opposed to in the face of a cyclist. The one in the highway will have impacts on the immediate natural surroundings, while the urban case will have an impact on the poor cyclist breathing in the toxic fumes. So, as I was saying, in LCA we would know the amount of exhaust gases, but we would not know in sufficient detail when or where they occur to create a realistic estimate. Hence, LCA gets around this by saying potential impacts.

My feeling with all this is that we now have tools like GIS, better computers and such. Let's start attempting to understand impacts and collecting relevant data. One part of me still thinks this may be a losing battle as going back to the exhaust example, some people may be affected differently by breathing in car exhaust. Is the cyclist me or my grandma? However, even in this last question, I am secretly proposing an answer as we can guess to some degree of certainty, what the likelihood of the cyclist being my grandma is... Anyways, all I'm proposing is that we should move to a more predictive stage rather than offering uncertain estimates that may misdirect our decisions from our true intentions.

This is not to say that all impact categories in LCA are like this. Global Warming Potential, expressed as kg of CO2e appears to be the one category where there is some consensus and standardization in its application. The difference, is that this impact is one of the more global ones.

Finally, I will just say that the biggest challenges I see to the application of LCA is that it truly does require a high degree of expertise. The most common way of doing LCA is through the use of software like Athena's Impact Estimator, which is focused on the conceptual stage and assembly based, or some more refined program like PRé's SimaPro which requires a lot more detailed input which can be even more time consuming and expensive (but perhaps more powerful and informative). My general feeling about all this is that we should go back and create models that require simpler, more reasonable input that gives us good estimates for conceptual stages and for analysis. A final comment is that SimaPro can handle most things, but it is tailored for products (buildings are very complex), while Athena is focused on buildings in North America.