FAQ'S

To be blunt, we're trying to get away from the habit of answering people's general questions about green building outside of our consulting or lecturing work. We have to be disciplined if we're going to get our paid work done and put bread on the table. Many of these questions are answered in the books and articles we write, so we usually just try to steer people toward the appropriate source. To our minds, green building is about awareness, which means you're going to have to take a lot of personal initiative to become aware. However, if in the process of our work we have an exchange that answers a general question that we think might be of help to others, we'll eventually post it here. Due to time constraints, this will have to be a work in progress. The following exchange is a sample of what you'll eventually find here:

Question:

I've heard that straw bale building is not well-suited for our Carolina/Georgia environment because of its tendency to get moldy. Should I stay away from earthen home options when building my house?

Answer from Clarke:

First let’s define our terms. To my mind, straw bale construction isn’t a form of earth building. I reserve that phrase for techniques like cob (a mixture of clay, sand, and straw), adobe, and rammed earth. In my opinion, the problem with earth building in our climate isn’t water but cold. Earth, like stone, concrete, and other heavy mass materials, is good at storing heat but not good at preventing its movement. That’s why I like to use these materials in the floor to collect solar heat as part of a passive solar design strategy, while using more insulative materials, like straw, to fill the volume of the walls.

There are two distinct approaches to using straw bales as insulation in walls: load-bearing or infill. Load-bearing straw bale construction, often called “Nebraska style”, entails stacking bales like bricks to create walls in which the bales themselves carry the weight of the roof and other loads such as those created by wind. I don’t recommend load-bearing straw bale construction in our climate mainly because it entails building bale walls without the protective cover of a roof. Completely soaking your bales with rainwater during construction is an excellent way to guarantee the mold problems that you’re wondering about.

The second type of straw bale construction involves building a skeletal structure like a stick frame, post and beam, or timber frame complete with roof, and then filling the open spaces between the framing with straw bales. In this approach, the bales are acting solely as insulation, a job at which they excel. I think that using bales in this way can be a sensible choice in our climate. Yes, bales can mold, but so can many other materials that are commonly used in conventional residential construction. As with any building approach, the devil is in the details. In order to build successfully with bales in our climate, you need to understand how water and humidity work and carefully create a design whose components function together to keep your bales dry. The details of how to do this are too involved to go into here and would have a lot to do with the specifics of your building site and personal housing needs.

© Clarke Snell, 2005