[GSBN] Fwd: Embodied energy comparisons: SB vs Stick-built

[John Swearingen]

Hi,

I did a quick simulation of a conventional house in Boston, 2000SF in size,
vs. an energy efficient one that uses "off the shelf" improvements (better
windows, furnace, etc.), and got a difference of 4.2 times the emission for
the conventional house.  In quantity, that's about 24,000 more pounds of CO2
emitted annually (31,292 vs 7,352), which is a striking difference.

If both of those houses were 50% larger, or 3000SF,  the emissions are
increased by about 30% (33% for the conventional and 28% for the efficient
one). You can get up to about 15,000 SF before the efficient house burns as
much as the smaller conventional house (but I wouldn't spread that around).
So size matters but  efficiency matters more.

 I've no idea how that compares with the carbon burned/sequestered during
construction, the "net" numbers, and would certainly be interested to know.

John

On Sun, Feb 15, 2009 at 10:51 PM, Derek Roff <derek at unm.edu> wrote:

> Thank you, Andrew, for replying to my concerns and questions.  I'd like to
> investigate two points a little further, if you are willing. The first is
> getting the 2x4 to the job site.  I see that I wasn't sufficiently explicit
> in my use of that phrase.  I was not thinking simply of transportation.  I
> was thinking of all the fuel burning, carbon releasing things that are
> required to produce and deliver that 2x4.
>
> My mental model begins when the tree is harvested with chain saws and
> perhaps larger scale motorized harvesting.  It is brought out of the forest
> with large diesel vehicles, then loaded on trucks for transport to a
> sawmill.  Road building is involved, whether this is a forest or a
> plantation.  Road maintenance is involved.  Tires are replaced, vehicle
> parts are replaced.  At the sawmill, we run the saws, and light/heat the
> buildings.  Sawdust and scrap are burned, more or less efficiently, which
> releases some of the carbon which had been stored in the tree.
>
> At some stage, the lumber is sent to the drying kiln, which also uses
> fossil fuel.  All of the office workers, sitting in their heated/cooled
> offices, are releasing carbon in order to help produce that 2x4.  Almost all
> the direct and indirect workers arrive and leave their workplaces by fossil
> fuel vehicle.
>
> The 2x4 goes to the planer.  It is graded.  It may be moved a few times in
> storage and warehousing.  It is transported in various steps, with repeated
> loading and unloading, until it finally gets to the job site.  Meanwhile,
> the harvest site is being cleaned up and prepared for replanting.  Slash may
> be burned, which has a greenhouse gas impact far worse than the simple CO2
> contained.  The new trees are planted.  Some level of care is expended until
> the next harvest.
>
> Each of the items in this chain had to be built, maintained, and at some
> time will be dismantled.  A little bit of carbon from each of these steps
> must be counted against the carbon stored in the 2x4.  At the point when we
> are ready to harvest again, we reach the beginning of the cycle, as I have
> delineated it.  Only then can we stop the meter on the carbon used to
> produce and deliver a 2x4.
>
> There are probably other factors that I have overlooked.  These were the
> kinds of things that I was thinking of when I said that I would be surprised
> if you could get a 2x4 to the job site with a negative (good) carbon
> balance.  I am prepared to be surprised again, but I wonder if all of these
> kinds of things included in your calculations, Andrew.  I would love to see
> the estimates on these factors.  Perhaps they will be in your upcoming
> thesis.
>
> I'd like to better understand this statement that you made:
>
> "The numbers in my report are net, to the factory gate. So, a negative
> number for timber indicates the overall CO2 that has been removed from
> the atmosphere."
>
> Please tell me more about what goes into the "net" numbers.  And is this
> "factory gate" the last milestone before the 2x4 heads to the job site, or
> is it earlier in the process?
>
>
> The other thing I would like to hear a little more about is Bill's question
> about building size and energy usage.  In the US, for the last 100 years,
> carbon released due to heating/cooling energy use during the building's life
> cycle has been many times the embodied energy of construction.  A larger
> house will waste more energy, and therefore release more carbon, using the
> fossil fuel energy sources that supply the overwhelming majority of homes.
>
> How can this be factored into the carbon sequestering discussion? How much
> difference would there be between an average new house, and a highly energy
> efficient one, in terms of the relative importance of size and carbon
> sequestering?
>
> Thanks again for sharing your time and information.
>
> Derek
>
>
>
> --On Monday, February 16, 2009 12:12 PM +1300 Graeme North <
> graeme at ecodesign.co.nz> wrote:
>
>  Hi Derek
>>
>>
>> Undoubtedly, building smaller uses fewer resources than building
>> large, if you are buildng with the same materials AND there is a net
>> carbon emission from those materials. But there are buts. The way to
>> get your head around this is to think from a global level down to
>> your
>> own building level. (Think globally, act locally.)
>>
>>
>> THE major (far and away) threat to the planet is climate change.
>> Yes,
>> OK, population (P), consumption levels (C), and the particular
>> impact
>> of the particular technology of consumption (T) are big issues
>> (I=PCT:
>> Ehrlich and Holdren). But the biggest way they are, in aggregate,
>> currently impacting on the planet is via climate change. Sure,
>> reducing P, C, and T reduces overall impact (I), and getting each of
>> them down seems a sensible aim. But while doing that, climate is the
>> pressing issue. The problem for the planet (which is not quite the
>> same as the problem for the humans) is that too much many GHGs are
>> being dumped in the atmosphere. So, if overall fewer GHGs can be
>> dumped into the atmosphere, and more GHGs can be removed from the
>> atmosphere, the better.
>>
>>
>> On that basis, if Jane and Joe Bloggs are going to build a house,
>> there is the potential for them to build it in such a way that it,
>> overall, removes CO2 from the atmosphere. They can do that by
>> reducing
>> the CO2 emitting materials and technologies, And by increasing the
>> ones that have a net absorption. They will have to work pretty hard
>> at
>> this, but it can be done. IF they build it bigger, and the extra
>> size
>> comes from timber, straw and other carbon-storing materials,
>> (shingle
>> roof, timber floor, timber window frames) then the net effect will
>> be
>> that their house has removed more CO2 from the atmosphere than it
>> has
>> emitted. This will include things like having their own solar hot
>> water system, probably their own on site electricity generation,
>> and a
>> few other things.  If the extra size also requires more aluminium
>> window frames (bad), more steel roof, more concrete floor, lots more
>> copper wiring and plumbing, then they may find they are emitting
>> more
>> CO2 overall. So, yes, bigger CAN be better.
>>
>>
>> One caveat here: my analysis has been done on NZ materials and
>> houses.
>> The Nth American situation will be different. But probably not that
>> different. Someone will just have to run the numbers. Perhaps later
>> in
>> the year I will be able to make an on-line calculator available that
>> will help in this regard, although getting the Nth American numbers
>> for materials is one challenge. Thermal analyses for different
>> cliamtes woud be needed too. (As a complete aside, does anyone have
>> a
>> guess if/how much people would be prepared to pay for such a gadget
>> -
>> that calculated the CO2 impact of a particular house design?)
>>
>>
>> OK Derek, be surprised: the CO2 released in getting a 4x2 out of a
>> tree, to the site, and into a house IS less (a lot less) than the
>> CO2
>> removed from the atmosphere and stored in that 4x2. Again, my
>> numbers
>> are from NZ, but Nth America will be pretty similar. The idea that
>> transport releases lots of CO2 is only true when you think about all
>> the cars and trucks running around. It is a fallacy that transport
>> CO2
>> emissions are a big part of the emissions for materials and
>> products.
>> Transport is almost always less than 5%, and frequently less than 2%
>> of the total. Basically it's a big red herring in this debate. Sure,
>> local is better, but other things are more important - like
>> aluminium
>> uses heaps of electricity to make, and timber doesn't. The distance
>> that aluminium has to be transported, even if it's twice around the
>> globe, is insignificant (like, right off the radar) compared to the
>> manufacturing energy and CO2.
>>
>>
>> The numbers in my report are net, to the factory gate. So, a
>> negative
>> number for timber indicates the overall CO2 that has been removed
>> from
>> the atmosphere.
>>
>>
>> Yes, indeed Derek. Your question "What would have happened to this
>> material if I hadn't used it in my house?" is an excellent one. The
>> best question in this regard is, I think, "What is the effect of
>> doing
>> abc or xyz?" If the effect of using a 4x2 to build your house is to
>> bring down a virgin forest, that ain't a good idea. Go forth and
>> protect virgin forests! But, in NZ, and I expect there too, timber
>> for
>> houses comes from plantation forests. When you cut them, they get
>> replaced. They're an on-going carbon removal system - as long as the
>> carbon in the timber gets sequestered, and not returned to the
>> atmosphere. That's how our atmosphere got to have the high
>> oxygen/low
>> CO2 levels it did - by forests turning atmospheric carbon into
>> below-ground carbon, as coal, oil and gas.
>>
>>
>> So, turn that tree carbon into houses and things. Then make sure the
>> houses last a long time and don't rot. And, make sure that at the
>> end
>> of the life of the house, the demolition timber either gets re-used,
>> or gets buried in well managed landfills that stop the timber from
>> rotting. (Then it's on its way to becoming coal, which, hopefully
>> won't get dug up and burnt in a few million years.) There is
>> evidence
>> that between 1 and about 25% of the carbon remains intact in the
>> timber after burial. (Depends on things like the moisture and oxygen
>> levels in the landfill - which can be controlled.)
>>
>>
>> Straw is basically the same story. If burnt or allowed to rot in the
>> paddock it returns its carbon to the atmosphere. If put into (dry)
>> houses, its carbon stays there. The by-product question is a bit of
>> a
>> red herring here. Whichever way you allocate the energy and
>> emissions
>> for the grain/straw, there's a net global carbon benefit from
>> sequestering the carbon in the straw into a house (or whatever).
>>
>>
>> And finally, absolutely agree about the large perspective.
>>
>>
>> Cheers
>> Andrew Alcorn
>>
>>
>
>
> Derek Roff
> Language Learning Center
> Ortega Hall 129, MSC03-2100
> University of New Mexico
> Albuquerque, NM 87131-0001
> 505/277-7368, fax 505/277-3885
> Internet: derek at unm.edu
>
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-- 
John Swearingen

Skillful Means
www.skillful-means.com
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