for your own project.
To this end, we’ve included a resource list at the end of each chapter to direct your research. These are references that we have found useful, but by no means do they represent the full depth of information available. Use these sources as a springboard and search for the resources that speak most clearly to your intentions.
In many chapters, you will find sidebars written by people with a particular straw bale building experience to share. These are individual takes on specific areas of concern, both technical and personal. As a growing movement, straw bale building is developed and passed on by so many knowledgeable, creative people that we thought a sampling of voices from the field would prove useful to those who are just being introduced to the idea.
Come on inside!
A Note to Experienced Builders and Straw Bale Enthusiasts
The world currently contains a disproportionate number of first-time bale builders compared to those who have experience! We’ve written this book principally as a guide for people who are undertaking a bale structure for the first time. For builders who have a depth of experience in straw bale building or other styles of construction, there will inevitably be some redundant information. Hopefully, there will also be much that is either new or approached from a different angle. We hope you take the time to find what’s useful to you. If you are a conventional building professional, we encourage you to try some bale work and then offer it to your future clients as an option. You might be surprised at the level of interest that’s out there.
Bales Aren’t Just for Houses
Throughout this book, we often use the word “house” to describe bale buildings, but by no means is the use of straw bales limited to single-family dwellings. From tiny garden sheds to large factories or warehouses, bales can be used in many ways to create many structures using the principles outlined here. If you find working with bales as addictive as we do, you’ll start creating needs just to have an excuse to make another bale building!
Taking the First Step and Engaging Your Brain
Building your own home is a sprawling process of input, suggestion, passion, necessity, compromise, error, change, and refinement. We hope that this book inspires and assists those who wish to leap into that sprawl, immerse themselves, and emerge with a home to be proud of.
So, in the name of inspiration, it’s onward we go .…
CHAPTER 1
Why Build with Straw?
Straw bale builders must repeatedly answer the question, Why?
Why bother using straw bales? There are many answers, and we’ll start by addressing the most common reasons for building with bales.
Straw as a Building Material
Not a Building Newcomer
Despite its relatively new status as a building material in North America, straw has been used in construction for as long as humans have been creating shelter for themselves. Durable, flexible, and grown close to the building site, unbaled straw is still widely used around the world in a variety of roof, wall and flooring systems.
Straw in Block Form
The horse-driven baling machine, invented and introduced into the grain-growing regions of the North American West in the 1870s, had the unintentional side effect of turning mounds of loose straw into tight, easy-to-handle building blocks. The settlers of the Nebraskan sandhills, who faced a lack of lumber and suitable sod for building their new homes, were the first to put these building blocks to use. Some of these early bale structures are still standing and occupied — a testament to the durability of straw bale walls and the community spirit. The settlers’ enduring and effective homes are responsible for the bale building we do today.
1.1: The Pilgrim Holiness Church in Nebraska is one of the oldest surviving historical straw bale buildings. It’s a testament to the durability of bale buildings, and also the community spirit of this kind of construction.
Straw Bales: The Waste that Rocked the World
Enough straw is currently produced every year in North America to meet all our residential building needs. And the same is true in many other parts of the world, since grain farming is common across most cultures and regions. This fact alone is enough reason to move toward using this abundant renewable resource for construction purposes, even if it held no particular advantage over other building materials. The fact that straw bale buildings can out-perform buildings made from other materials and lighten the load on the planet, as well as on our pocketbooks, makes it a triply effective material with which to build.
What’s in an “R”
Let me offer a slightly different take on what is likely happening with the R-value of a straw bale wall. I question whether the best, most controlled scientific testing would show anything like the R-50 that we have all heard about for [three-string, 24-inch-wide] straw bales. The test used gives a fair first approximation but is widely recognized as being less accurate than ASTM236 Hot Box testing. That said, the difference between R-30 and R-50 is really not that great. It is certainly less than the difference between R-10 and R-30, an apparently equally distant pair of values. This is because R-value, a number derived from U-factor, is the ability of a substance to resist heat flow. To understand how that plays out in actual performance, we need to convert R-values back to U-factors, the measure of how much heat flows through a substance under a predefined set of conditions. U-factor is 1.0 divided by R-value and vice versa.
An R-10 wall will allow 1/10 of one Btu (0.10 Btus) through one square foot of wall in an hour if there is a one-degree Fahrenheit temperature difference between the two sides of the wall. An R-30 wall will allow 1/30 of a Btu (0.033 Btus) through under the same conditions. An R-50 wall will allow 1/50 of a Btu (0.02 Btus) through. Obviously, if your wall is R-10, you are going to make a much bigger dent by increasing the R-value to R-30, than if your wall is R-30 and you move to R-50. It’s the law of diminishing returns. At some point, common sense and the pocketbook say it’s good enough.
However, the tested R-value has little to do with how the wall performs in the real world. This is much truer for straw bale walls than for stud walls. Thermal bridges occur with regularity in stud walls — in fact, at every stud. Straw bale walls have fewer thermal breaks, by far. Moreover, the R-value is measured under what can be called static conditions: you can only take your readings once the wall surface temperatures have stopped changing. This takes about 20 minutes for the average window, an hour or two for a wall, and three to seven days for a straw bale wall. In other words, the conditions at the two wall surfaces must not change for days on end, or the R-value is invalid. Well, how often in the real world does that happen with one’s house? The time it takes heat to travel through a straw bale wall is about 12 to
