[Strawbale] appropriate PC

[Rene Dalmeijer]

Dear flaxstraw,

Pc or even Fly ash cement is an open nerve on this list. As it is one 
of the products that is very difficult to avoid specifically in 
foundations. (not to forget the steel rebar). Many people on this list 
strive to minimise embodied energy (CO2) used in building their 
ecological house. Some push the envelope by limiting the use of high 
embodied energy materials altogether I am happy they do, as effectively 
I hope they are able to successfully push the envelope. The obviously 
ridiculous idea of using straw bales to build a house is a good example 
of envelope pushing Everybody is free to choose the level of greenness 
they seek.

What I personally strive for is a balance between low ecological impact 
(based on full life cycle analysis LCA), comfort and the fact that it 
should be possible in a heavily built up environment ie a city suburb. 
This means the foundation (and concrete piles) and ground floor use a 
substantial amount of fly ash cement (fly ash is not special here but 
the norm) and a prefab concrete/EPS floor system (this system uses the 
least amount of cement possible for a stone ground floor. These choices 
off course are strongly determined by local circumstances. Besides this 
the rest of the house is built using renewable/re-growable materials. I 
also have some mechanical systems like a heat pump and an ERV system 
but based on LCA this is not a bad deal and yes I use steel screws .
I would like not to use the cement in the foundation and ground floor 
but see no other suitable alternative as yet.

BTW It is possible to use pure lime plaster forgoing the use of any 
cement. But then again using lime instead of cement is not such a big 
deal. Can anybody say how much CO2 a pure lime plaster saves compared 
to a cement plaster?

As HW states transport can have a tremendous impact on the CO2 balance 
of so called green materials. The off-grid deep green house might be 
not so green as a std high rise downtown apartment once you take all 
the commutes into account, and how about LCA of the road to the off 
grid house?  Just  imagine what would happen if all we green folks move 
out of town is that a good idea, I doubt very much.

Times are changing what we do has consequences we are now more aware of 
then ever before. I hope we personally make the right choices for 
ourselves before beleaguering others with how they should make their 
choices.

Rene
On May 9, 2007, at 19:00, strawbale-request at listserv.repp.org wrote:

> It never ceases to amaze me that when anyone mentions cement that
> everyone goes on and on about how it is the root of all evils. Well
> it isn't. When we talk about cement stucco every limehead forgets
> that there is one part cement, two parts lime and six parts sand. Now
> if that isn't a lime stucco with a cement additive I don't know what
> it is. Furthermore, when people talk about cement stucco failures
> they forget to mention that it was placed on and forgotten whereas
> lime stucco must be tended to every few years or it will also fail.
>
> If we are going to compare products, please compare all components of
> the materials life cycle