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

[Graeme North]

Andrew replies to Derek


Graeme
Graeme North Architects
49 Matthew Road
RD1
Warkworth
tel/fax +64 (0)9 4259305

graeme at ecodesign.co.nz
www.ecodesign.co.nz


Begin forwarded message:

>
>
> 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
>
>
>
>> I'm a bit concerned by what I understood from the summary.  It  
>> seems to say
>> that it is better/greener to build a bigger house, at least one  
>> with more
>> materials, such as straw plus wood frame.  While straw and wood  
>> both contain
>> carbon, I would be surprised if you could get a 2x4 to a job site  
>> in an
>> industrialized country without generating/releasing a lot more  
>> carbon into
>> the atmosphere than is contained in the board.
>>
>> Another aspect of the calculation should be, "What would have  
>> happened to
>> this material if I hadn't used it in my house?"  The average 2x4  
>> would still
>> be a tree, which would be much better for the environment.  Straw  
>> is a
>> little harder to pin down, since it is a by-product of growing  
>> grains.  If
>> we compare building with straw to burning it, building has a great  
>> greenness
>> advantage.  If we compare building to leaving the straw in the  
>> field, the
>> difference is much smaller, and might favor leaving the straw in  
>> the field.
>> In any case, we know that straw would not live on for another season.
>>
>> I believe that smaller is better/greener, when it comes to  
>> building design,
>> and a larger perspective may be needed in analyzing the importance  
>> of carbon
>> sequestering.  Have I misunderstood Andrew's summary?
>>
>> Derelict
>>
>> 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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