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.
Monday, May 31, 2010
Saturday, May 22, 2010
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.
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.
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.
Friday, May 21, 2010
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.
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.
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