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Thread: Energy efficiency of mid-rises vs. high-rises

  1. #1
    Cyburbian
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    Energy efficiency of mid-rises vs. high-rises

    Is there a definitive answer to the question of which is more efficient? Would one 18-story building be more energy efficient than three 6-story buildings?

  2. #2
    Cyburbian Emeritus Chet's avatar
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    It all depends on the construction, not the size or multiples.

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    Dan Staley's avatar
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    Quote Originally posted by PatrickMc View post
    Would one 18-story building be more energy efficient than three 6-story buildings?
    That is far less than enough information to adequately answer the question.

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    Cyburbian
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    Okay, I should have been more specific. What I meant was, all other things being equal, which is more efficient - high rises or low rises.

    Assume square footage per dwelling is equal. Other things like consumption patterns of residents will be assumed to be equal.

    What I'm trying to figure out is whether or not the per-capita energy use of mid-rise buildings is lower than that of high-rises.

  5. #5
    Cyburbian CJC's avatar
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    There are still a lot of other factors that come into play. Are you talking efficiency of construction or operational use or both?

    For example - an 18 story building needs a larger foundation, but probably not three times as large, so fewer resources would be used there. Assuming the same footprint, clearly the 18 story building is going to use 1/3 of the roofing materials. In a cold climate, an 18 story building will likely be more efficient to heat, because less heat is lost through the top compared to three smaller buildings with the same size footprint.

    On the other hand, an 18 story building will likely have more space set aside for elevators (probably two 18 story shafts, compared to three six story shafts) and the elevators will be used more.

    Those a just a few things I can think of right now, but there are countless others. Is parking for all structures underground or off-site? In the case of underground, the 18 story building probably wins again, if parking is nonexistant or off-site, it's basically a wash on that issue.
    Two wrongs don't necessarily make a right, but three lefts do.

  6. #6
    Cyburbian TexanOkie's avatar
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    PatrickMc is not asking whether high rises or mid rises are energy efficient. He's asking whether two buildings built to the same specifications, including parking (location and appropriate optimal ratio for building size) etc, are just as energy efficient if one is 6 stories or if one is 18 stories. Is there something intrinsic about either mid-rises or high-rises that would grant one to being more energy efficient, assuming all construction, siting, and technologies utilized were equivalent?

    P.S. I do not know the answer to the question.

  7. #7
    Cyburbian
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    Thank you, TexanOkie. That is what I'm trying to figure out

  8. #8
    Cyburbian
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    I guess you could look at it this way:

    If you were going to build a town of say 20,000 people, what would the most energy-efficient set up be?

    Obviously not a lot of detached houses spread over a wide area and requiring cars for transportation. So that can be ruled out.

    One giant high rise containing everything - an arcology?

    A cluster of high-rises (20-50 stories)?

    smaller high rises (7-20 stories)?

    A group of mid-rises covering a wider area?

    remember, square footage and consumption patterns are equal so those can be ignored.

    I'm interested in a life-cycle analysis including the cost of construction and the operating costs over the expected lifetime of the building(s). If anyone has any info regarding this it would be appreciated.

  9. #9
    there has been a lot of talk about this issue, but very little solid research. I have been looking for a believable analysis but have yet to find one.

  10. #10
    Dan Staley's avatar
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    Quote Originally posted by PatrickMc View post
    I guess you could look at it this way:

    If you were going to build a town of say 20,000 people, what would the most energy-efficient set up be?
    Energy efficient now, or in 20 years after peak oil and in 30 when carbon will be severely limited (presuming no breakthru scrubber technology)? In this case, it will be difficult to lift boxes 250 feet in the air 12 times an hour at peak. [/technology pessimist]

  11. #11
    Cyburbian
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    Quote Originally posted by Dan Staley View post
    Energy efficient now, or in 20 years after peak oil and in 30 when carbon will be severely limited (presuming no breakthru scrubber technology)? In this case, it will be difficult to lift boxes 250 feet in the air 12 times an hour at peak. [/technology pessimist]

    Dan, do elevators really consume that much energy? Would it not be feasible to power them with solar panels and wind turbines built into the building itself? Would this increase the embodied energy of the building to the point where it wouldn't be worth it? In other words would the cost of installing all that equipment be paid for through lower operating costs over the lifespan of the building?

    If what you are suggesting turns out to be true, than the best setup would seem to be a bunch of mid-rise buildings. Even if they had elevators, they don't have to go as far so they would not consume as much energy. With a 4 story building you may not need elevators at all.

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    Cyburbian DetroitPlanner's avatar
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    It takes quite a bit of energy to lift heavy things against gravity. You can try this yourself by simply lifting a Chevrolet Cavalier over your head and carrying it up stairs. Now put the Chevy in nuetral and push it. Which takes more energy?

    A four story building would require elevators per ADA requirements. Accessiblity is very important. Whats the sense of building something that 10 to 20 percent of the US population would find difficult, if not impossible to use?
    We hope for better things; it will arise from the ashes - Fr Gabriel Richard 1805

  13. #13
    If there isn't going to be enough energy to run elevators (don.t forget the counterweights by the way), then there is certainly not going to be enough energy to keep single family homes livable.

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    Cyburbian CJC's avatar
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    Quote Originally posted by DetroitPlanner View post
    It takes quite a bit of energy to lift heavy things against gravity. You can try this yourself by simply lifting a Chevrolet Cavalier over your head and carrying it up stairs. Now put the Chevy in nuetral and push it. Which takes more energy?
    One word - counterweights The biggest energy usage of practically any building is going to be heating/cooling, especially if you include the heating and cooling of food and water in with that. Compared to heating/cooling, other things like computers, TVs, light bulbs (especially when talking CFLs), and yes, even elevators, are pretty small parts of energy usage. I spend less than 10% of what my parents spend on utility bills, even though I have more gadgets that use electricity. I simply live in an area and a building that requires no heat or A/C, where they live in an area that has 5-6 months of heavy heating and 2-3 months of A/C.

    In the modern world, I can't imagine that an 18 story building would not be more efficient than three six story buildings, but I don't have facts to back it up. It just seems obvious based on development patterns in developing countries - the megacities of Latin America and Asia are made up of miles and miles of shantytowns, based around miles and miles of 20-30 story buildings (primarily). In places where efficiency doesn't matter as much because of wealth, you'll see SFH development like the US or scaled development like Europe (where they have attempted to match pre-industrial scale). I'm a big fan of European scale, just because it is closer to human-scale, but I would assume that places that care much more about energy cost would be building the most efficient way using widespread (affordable) modern technology.

    Edit - I see Gotta Speakup got to that first part first...oops
    Last edited by CJC; 24 Feb 2009 at 7:28 PM.
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    Dan Staley's avatar
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    Quote Originally posted by Gotta Speakup View post
    If there isn't going to be enough energy to run elevators (don.t forget the counterweights by the way), then there is certainly not going to be enough energy to keep single family homes livable. [emphasis added]
    We already know that shared walls reduce energy consumption, as well as shared floors.

    Whatever mode we choose - and IMHO I'm not sure it will be 18-story residences for a decent fraction of the population - it is clear that the inefficient buildings of the past are not going to help anyone. I see, soon, wide adoption of IBC-type codes for minimum R-values for walls and roofs, and maybe not Ar windows but something similar. Soon we will be renting IR cameras for our houses.

  16. #16
    Buying housing should not be a majority vote kind of thing like voting for president. It is more like buying a cell phone carrier. There are what, a dozen major companies? We dont say a majority want Verizon therefore everyone must have Verizon.

    It should be the same for housing types. If only 10% or 20% or whatever want to live in high rise housing, than the economy should provide that much high rise housing. Right now it is not, its a market failure in most metro areas that you can't choose to live how you want to live.

  17. #17
    Member Martin's avatar
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    The answer is... it depends.

    There are a couple of studies that show that mid-rises are more efficient than high-rises, per square foot, per person, and per household. This one in Australia http://www.basix.nsw.gov.au/informat...peak_multi.pdf
    There was one in Canada that I can't find, but here is a summary of some of its findings:
    http://www.cmhc-schl.gc.ca/publicati...tech/97100.htm

    The U.S. data is more abundant but less clear-cut. You can find it here:
    http://www.eia.doe.gov/emeu/recs/rec...es2005c&e.html

    There are also studies from eastern Europe saying the same, but these are less relevant to US conditions.

    The Australian study has the most thorough methodology; it measures all energy use, metered and unmetered, individual and shared.

    The energy difference between mid-rise and high rise is not as clear in the US data, but apartments in general use more energy than most other forms including, surprisingly, single family homes.

    There have been many theories proposed, including elevators, lights on all night, less control over heating and cooling, the properties of concrete, the tendency to have indoor pools, etc. One of the physical factors is "stack effect". Essentially, the weight of a column of air or water in ducts or pipes exerts pressures and affects temperatures in a way that takes a lot of energy to overcome. Small leaks that develop in ducts and cladding have a major effect on the energy required to heat, cool, ventilate and dehumidify. If you're asking about low-rise, not mid-rise, walkups definitely use less energy - no elevator, less common space, fewer shared facilities.

    In theory, larger projects have the economies of scale to implement more efficient heating, cooling, hot water, and things like geothermal. In theory but not in practice.

    There is also the embodied energy, the energy cost of construction, which is higher for concrete and steel than wood frame. From a life cycle point of view, high-rises are also the least adaptable for re-use and the least recyclable. Exactly what is the relative lifecycle cost is a very tricky calculation, with wildly different results depending who is doing it. In earthquake areas highrises require a lot more materials per unit than elsewhere. And are you counting pavement, electrical lines, landscaping water and the like, which are location-dependent?

  18. #18
    Dan Staley's avatar
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    Quote Originally posted by Martin View post

    (snipped throughout)

    There are a couple of studies that show that mid-rises are more efficient than high-rises, per square foot, per person, and per household. This one in Australia http://www.basix.nsw.gov.au/informat...peak_multi.pdf
    There was one in Canada that I can't find, but here is a summary of some of its findings:
    http://www.cmhc-schl.gc.ca/publicati...tech/97100.htm

    The U.S. data is more abundant but less clear-cut. You can find it here:
    http://www.eia.doe.gov/emeu/recs/rec...es2005c&e.html

    The energy difference between mid-rise and high rise is not as clear in the US data, but apartments in general use more energy than most other forms including, surprisingly, single family homes.

    There have been many theories proposed, including elevators, lights on all night, less control over heating and cooling, the properties of concrete, the tendency to have indoor pools, etc. One of the physical factors is "stack effect". Essentially, the weight of a column of air or water in ducts or pipes exerts pressures and affects temperatures in a way that takes a lot of energy to overcome. Small leaks that develop in ducts and cladding have a major effect on the energy required to heat, cool, ventilate and dehumidify. If you're asking about low-rise, not mid-rise, walkups definitely use less energy - no elevator, less common space, fewer shared facilities.


    There is also the embodied energy, the energy cost of construction, which is higher for concrete and steel than wood frame. From a life cycle point of view, high-rises are also the least adaptable for re-use and the least recyclable. Exactly what is the relative lifecycle cost is a very tricky calculation, with wildly different results depending who is doing it. In earthquake areas highrises require a lot more materials per unit than elsewhere. And are you counting pavement, electrical lines, landscaping water and the like, which are location-dependent?

    (emphases added)
    First, excellent reply.

    The measurement of CO2 suffers when consideration is per capita, as there are fewer captias in apartments, with the reduction in space not being an equal ratio. I suspect some of these larger SFDs that lose a teenager capita or two might find a different emission number as well.

    Nonetheless, a key point here that was not hammered on above is the embodied energy, leading to life-cycle costs - perhaps the best metric on a cubic meter basis.Using the life-cycle cost with the chance of adaptive reuse or ease of teardown for recycling material is a far better metric for sustainability purposes than simply calculating how much energy at a point in time dwelling A vsdwelling B uses.

    Thank you for the reminder.

  19. #19
    But how often do any dwellings get torn down? The recycling of building materials also happens so far in the future that the discounted value of reuse is probably real small. It would have to be way less than construction, operating, and other (energy use for getting goods and services to the inhabitants).

    This is a very valuable discussion.

  20. #20
    Cyburbian CJC's avatar
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    Per capita figures are hard to use, simply because the trend in this country is for families to live in SFH's and singles/childless couples to live in apartments or multi-family structures. Younger people waste more energy on stupid things - I don't have figures for it, but I would imagine that this would have to be true. How many times did your mom yell at you to close the door to keep the cold air out (or hot air out or whatever)? I remember my first dorm room and how awesome it was that I could crank the heat up when it was freezing outside and no one would yell at me!

    There are some other natural tendencies that will also play out - more SFH's are owned rather than rented, so investment in energy-saving devices is more likely to happen. To a landlord who owns an apartment building, but has the tenants pay their heating bills, the incentive to invest in this kind of stuff is much lower - even at the new construction phase. To a tenant, it may be on their list of questions, but paying $20 more a month in utility bills is unlikely to sway their decision on which apartment to rent. There just aren't the natural incentives built up. I would imagine this gets even more true in lower income or subsidized housing, where tenants are not paying the full market amount for their usage.

    I think we need to look at things demographically-adjusted, or at least comparing for-sale housing with other for-sale housing - bringing rented housing into the mix is going to distort things. Comparing a 1000 sq ft condo in Boston to a 1000 sq ft SFH in a neighboring community (hopefully of similar resale value) might be a little more apples to apple, especially if you could narrow age ranges and family makeup. Comparing all multi-family to all SFH's is not a fair comparison.
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    CJC, I think you are making a generalization about many Latin American Cities regarding development patterns. A simple GE image can illustrate that. In cases like Mexico City, São Paulo, which are some of the more populous cities in the world, you are very correct. You observe miles and miles of 20-30 story buildings. But then again look at that same image say, at the 10 mile scale, of NYC (another very populous city) and you can see the same images. If you go to Asian cities like Tokyo (another Populous City) again very similar images. Please keep in mind these are simple observations without looking at any data compiled by studies. As mentioned by someone before, better comparisons may be made when comparing apples to apples.

    However, I do agree with you. Not ever having visited Europe and any of its cities I too am a fan of their patterns of development. If you ask why, I would say that they have been able to keep a more urban lifestyle. A pre industrial scale as you put it. Is it more efficient lifestyle? Maybe. I certainly seems to be less lavish to what we have been accustomed here I the States. Public transportation is abundant, affordable, and used by most of the population even when traveling from city to city. They also tend to live for the most part in ‘flats’ or ‘pisos’ as opposed to SFH that we have been accustomed to here in the States. Leave it to the 'Old World' to teach us through experience.

    And touching on the energy efficient building subject. I guess that as some have mentioned here, location and the ambient temperature and climate will play a very large role. In Guatemala City, which is a City I’m very familiar with, the temperature is Spring like all year round. That makes heating and cooling optional for most small constructions. This is not the truth for all of the country. Due to its very dramatic topography, Guatemala has many micro climates; ranging from hot, humid tropical weather in the costal lowlands to the highlands which may reach below freezing weather in the Northern hemisphere’s winter months .

    BTW, I am fairly new to cyburbia and I’d like to thank all here as I have learned a lot from surfing through all the threads.

  22. #22
    Member Martin's avatar
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    Comparing apartments to single family homes is just interesting trivia, not useful information. The two markets are not interchangeable like different heights of apartment buildings. Both apartment buildings and SFHs will be built and both should be made made efficient, you can't give up on one form and tell people to move into the other.

    On the question of life cycle, residential high-rises have a remarkably short average lifetime, I'm told, compared to other buildings. Since the embodied energy of buildings ranges from 15 to 40 years worth of operating energy, a building that lasts 25 years and is not recycleable uses twice as much energy on an annual basis averaged over the life cycle than one that lasts 50 years and is partly recycleable.

  23. #23
    Cyburbian CJC's avatar
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    Quote Originally posted by Martin View post
    On the question of life cycle, residential high-rises have a remarkably short average lifetime, I'm told, compared to other buildings. Since the embodied energy of buildings ranges from 15 to 40 years worth of operating energy, a building that lasts 25 years and is not recycleable uses twice as much energy on an annual basis averaged over the life cycle than one that lasts 50 years and is partly recycleable.
    I've heard this too, but I wonder how much of it is because of where and how residential high-rise buildings were primarily built over the past half century or so. Commie blocks, housing projects, etc were all cheaply built highrises, but were probably the majority of residential highrises built in the US and Canada during the postwar period up to about ten years ago, at least outside of Florida and Hawaii. I would bet that Japan would be a good place to look and see what the average life of a quality residential highrise really is.
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  24. #24
    Cyburbian Brocktoon's avatar
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    Quote Originally posted by PatrickMc View post
    I guess you could look at it this way:

    If you were going to build a town of say 20,000 people, what would the most energy-efficient set up be?

    Obviously not a lot of detached houses spread over a wide area and requiring cars for transportation. So that can be ruled out.

    One giant high rise containing everything - an arcology?

    A cluster of high-rises (20-50 stories)?

    smaller high rises (7-20 stories)?

    A group of mid-rises covering a wider area?

    remember, square footage and consumption patterns are equal so those can be ignored.

    I'm interested in a life-cycle analysis including the cost of construction and the operating costs over the expected lifetime of the building(s). If anyone has any info regarding this it would be appreciated.
    Why would a town of 20k need an 18 story building? Once you get over 3 stories the cost to build a building goes up exponentially. For your question cost of land will dictate whether you build 3 building with 6 stories or one building with 18 stories, as will soil, the solar profile of the buildings. Look at the Manhattan skyline, there are many reasons why there are high rises clustered around mid town and downtown. Other factor is the end user, projected absorption of the property, its classification (A,B, or C).
    "If you don't like change, you're going to like irrelevance even less" General Eric Shinseki

  25. #25
    Cyburbian CJC's avatar
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    Quote Originally posted by GUAPHLPIA View post
    CJC, I think you are making a generalization about many Latin American Cities regarding development patterns. A simple GE image can illustrate that. In cases like Mexico City, São Paulo, which are some of the more populous cities in the world, you are very correct. You observe miles and miles of 20-30 story buildings. But then again look at that same image say, at the 10 mile scale, of NYC (another very populous city) and you can see the same images. If you go to Asian cities like Tokyo (another Populous City) again very similar images. Please keep in mind these are simple observations without looking at any data compiled by studies. As mentioned by someone before, better comparisons may be made when comparing apples to apples.
    Oh, I'm certainly generalizing. However, I have spent a pretty good amount of time in South America (not as long in Central America, though I have been to Guatemala, Honduras, Costa Rica, and Belize for short periods of time), and I think you'll find that even many smaller cities in South America have miles and miles of 20-30 story buildings. I'm talking about cities in Brazil like Fortaleza, Recife, Manaus, Belem, Natal, Curitiba, and Porto Alegre, cities in Venezuela like Valencia, Maracaibo, and Barcelona, and cities in several of the other countries as well. These aren't mega-cities, but cities with populations from 500,000 to 3 or 4 million. I've seen the same in many developing east Asian nations - it seems to me to be something more than just a mega-city thing.

    Welcome to Cyburbia, by the way!
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