Cohousing-L Mailing List: Re: Straw bale, Rastra block

[Lynn Nadeau (welcome]

At RoseWind Cohousing we have a two-story owner-built hybrid strawbale  
house. They liked it and so do the folks who bought it from them.

When we were contemplating the construction of our common house, we  
evaluated straw bale construction for it. We had Chris Stafford, a  
major strawbale guru, talk with us. I remember him telling us things  
that shifted our thinking. This was ten years ago, but I assume much  
of it still holds.

We are in the Northwest. In this area, straw is not a trash commodity,  
not burned, but has a healthy market among horse raisers, mushroom  
growers, and Japanese mat makers. So it's not all that cheap. The  
easier- to-use smaller bales are also the more expensive ones, too.

The deep window reveals, the thick-wall look, feels special to many  
people. In function, it works best when you are trying to minimize the  
effects of the hot sun. In our climate, we want to maximize how much  
sun gets in.

How well insulated your building is, is related to a lot more than the  
R value of your walls. Our common house is, in effect, a glass box,  
with walls full of doors and windows. And of course glass is very low  
on the insulating scale. As is all the coming and going and opening of  
doors. The insulation in your roof may be more important that that in  
your walls.

The typical exterior finish for strawbale is stucco. This is low  
maintenance, in the long run, though more expensive to install.

Our common house was not built of strawbale, but of Rastra block, a  
type of large building block made of ground up styrofoam and concrete.  
Also called EnerGrid. Not ideal, environmentally, in that concrete is  
energy intensive to make, and in our case the blocks had to be trucked  
long distances to get here. But like straw, the insulating value is  
high, and the use of wood is reduced. Similarly, too, our exterior is  
stucco, and much of the interior is Structolite, a plaster.

Like straw, channels need to be made in the walls at the outset for  
electrical and plumbing stuff, as well as blocking where you want to  
attach stuff later. Otherwise, retrofitting is much more complex that  
putting things in, or on, the walls of wooden structures. Many people  
like the free-form waviness of hand plastered walls, and it's  
interesting to make cool niches, arches, rounded edges. On the other  
hand, cabinetry and such has a flush back, and mounting flat things on  
wavy walls is a challenge.   Lots of forethought pays off well.

Lynn Nadeau
Port Townsend WA
where we have a sunny, spacious home for sale, photos on our web site 
www.rosewind.org