[Greenbuilding] Earth block wall section

[Stephen Collette]

Hello everyone.

I have a good friend who is a civil engineer running a great  
renewable energy company here in Peterborough, ON (between Toronto  
and Ottawa) and he is building an addition to his century cottage.  
(Had to, since his shop/office is larger than his house right now,  
the missus was going to have his head on a platter if he didn't do  
something). He has a very interesting idea for a wall system. He  
explains it a little below, which is why it's attached, however his  
pdf drawing explains it better. I'm not going  to try to draw those  
little x and o drawings that some of you are very good at, so I will  
describe the wall system from the inside out. I'd be interested in  
anyone's feedback and thoughts on this interesting design idea.

Proposed wall system from the inside out.

8 x 8 timber post and beam. Posts inset from slab edge by 1.5"
1/2" plaster finish.
Earth block wall. 4". We have a friend who has an adobe block machine  
up our way, and that is the proposed method.
2 x 4 strap wall.
Sprayed in place polyurethane foam wall. 4.5"=R22
Horizontal wood siding tied to 2 x 4's.

I know there is a measurement that doesn't work with the spray foam  
and the studs. There is a gap and I don't know what it is, and it  
isn't labelled on the drawing he sent me. (pdf available to all  
interested).

My concerns are the spray foam and adobe together. I'm a bit hesitant  
on that combination. But I don't  know how well the two materials  
will play together. His other questions are minor to the fact of  
whether this wall system would actually function in a varied climate  
such as ours.

I appreciate any input and interest.

Stephen


Stephen Collette B.B.E.C. - Principal
Your Healthy House - Indoor Environmental Testing & Building Consulting
www.yourhealthyhouse.ca
stephen at yourhealthyhouse.ca
705.652.5159


>
> I've come up with a wall section that I'd like to try out on our new
> addition here next summer (see attached pdf).  Essentially it's a
> combination of earth block wall and sprayed in place polyurethane foam
> (structure is timberframe).
>
> I've heard anecdotedly about a similar wall configuration being  
> used in BC
> by rammed earth builders, geodesic dome builders also do something  
> similar
> across the USA, but I've not heard of anything more local.
>
> Scientifically, I think it should be OK:
> - dew point is safely contained within insulation
> - no thermal bridging (except maybe with brick ties back to 2x4  
> strapping -
> not drawn)
> - earth blocks will never see freezing temperatures
> - spray foam offers air barrier and vapour barrier
> - earth blocks will hopefully absorb and release seasonal interior  
> humidity
> (and give plenty of thermal mass)
>
>
> I have some questions/concerns I'm hoping you can help me with:
> - Will earth blocks be able to adequately breathe given one side is  
> covered
> with polyurethane?  Do they need to breathe to the outdoors?
> - What kind of plaster might I use for a reasaonably smooth  
> interior finish?
> - Can I mix earth blocks and clay bricks? (I've got a ton or two of  
> old
> Peterborough clay bricks lying around here that I'd like to get rid  
> of)
> - What about mortar?
>
> I'm curious for your feedback.  Would you mind giving it some thought?
>
> best regards,
>
> Simon