Cohousing-L Mailing List: EnerGrid/ Rastra block construction material

[Lynn Nadeau (welcome]

>Lynn, what are EnerGrid blocks and what do they have to do with being in
>Washington State?
>
>--Diane
>  Jamaica Plain Cohousing, Boston, Massachusetts
>
>- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
>>We used EnerGrid blocks, which probably raised the construction cost,
>>>compared to stick framing. We're in Washington State.

That we are in Washington State is an unrelated fact (one Stephanie 
wanted in the psf costs). 

EnerGrid, also known as Rastra Block, is a wall-construction material 
made of concrete and ground-up recycled styrofoam. It comes in long bars, 
a bit like giant cinder blocks or Legos. 
The bars have holes cut at intervals, so when you stack up a wall, you 
have vertical hollow channels. Steel rebar rods are placed upright in 
these channels, and concrete is poured around them, creating reinforced 
concrete "pillars" at intervals in the walls. The block material itself 
is slightly crumbly, and can be cut with a saw, knife or other carving 
tool, which can lend itself to creative trim details, and also allows 
blocks to be cut to size.

The wall has its insulation in the material itself, like strawbale 
construction, unlike standard wooden construction which has an inner and 
an outer layer, with insulative filling of fiberglass, cellusose or 
whatever inserted in between. 

ADVANTAGES and DISADVANTAGES
+ saves trees
- indoor framing is still wood
+ uses concrete, which some say is environmentally good
- uses concrete, which has a high energy cost in making the cement
- blocks we used had to be trucked from Mexico (with fossil fuels); I 
think it now has to be trucked from the Southwest somewhere.
- because of that, you also can't just run to the lumber yard for some 
more
+ is well suited for owner-builders, especially if you have some 
afficionados of the material who will organize the team effort in a 
knowledgeable way
+ if you have local interest, you can get volunteers who will help, as a 
way of gaining experience with the techniques
- regular contractors have no experience with it
+ high insulation value
- wall insulation less important than roof insulation, and if you have 
walls full of glass windows and doors, they defeat the goal of avoiding 
heat loss
+ allows creative detailing
+ logical exterior finish is stucco, which is very low maintenance into 
the future
+ stucco is expensive, unless done by volunteers  (we did volunteers, 
with a few paid leaders)
+ logical interior finish is Structolite plaster, which is amenable to 
shaping, arches, and creates a somewhat hand-made-looking finish, with 
interesting texture.
- Structolited walls are vulnerable to chipping and cracking when you 
want to nail or screw things into them, but it can be done
- Structolited walls are not truly flat, which makes it hard to get 
cabinetry or such flush.
- attaching things to Rastra walls required special masonry anchors, or 
foresight in installing wooden blocking in strategic locations, before 
plastering. 
- electrical and plumbing in the walls requires pre-planning, with 
channels left open or routed out; later additions are less simple than in 
stud walls
+ the material is fireproof
- it costs as much or more than wood framing in an area where 
construction wood is readily available

Some people think this is a super-environmentally-sensible material. 
Obviously, my support is more qualified. Given our particular 
circumstances, it worked well. (Members in the construction trades who 
love working with it and converting others to their passion; lots of 
interest in detailing; others in town who wanted to volunteer and learn; 
volunteers for stucco and plaster work. )

We also have two houses at RoseWind built of Rastra. The local Unitarian 
congregation had recently built their church and parish hall using Rastra 
and nearly-all volunteer labor, and we had the same contractor coordinate 
our project. One of the RoseWind houses is shown in the recent 
coffee-table book, The New Cottage Home, by Jim Tolpin. The stucco was 
left gray, and ground up oyster shells were thrown at it while it was 
wet, creating a finish my sister says in Georgia is called "tabby". That 
book also shows how they carved fake-stone trim for the corners of the 
cottage. 

Hope that helps. There must be a web site, but I don't know which. 



Lynn Nadeau, RoseWind Cohousing
Port Townsend Washington (Victorian seaport, music, art, nature)
http://www.rosewind.org
http://www.ptguide.com

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