I recently received a list of questions from someone doing a report on straw bale construction for his college. His questions were good so I thought I would share my answers with you all here. You can read both the questions and answers below.
Q. From your experience, is straw bales as a building material user friendly? Can anyone learn to build with it?
A. Absolutely. I teach people how to build with bales every year at my seven day workshops. Those people range from professional builders, architects and engineers to home owners who are CPAs, teachers, computer programmers and more. Anyone can learn this technology.
Q. What current obstacles in building codes are blocking the use of straw bales in home construction? How can these be overcome? [Example: Here in Greene county MO, I was told I couldn’t build a load bearing straw bale structure because their adopted codes have no guidance for it. They did say I could build a post and beam style.]
A. It’s really about lack of education and understanding of the technology. The construction technology itself is fantastic; however, there are still too many people who either have not heard about straw bale construction, or are under educated about it and believe the rumors they hear. I’ve heard of people talking about what a fire risk straw bale structures are when, in fact, they have exceed conventional construction burn ratings in independent ASTM testing. The problem is that not enough positive MAIN STREAM media coverage has been given to this building technology. It is always viewed as “alternative” and as long as it holds that title, it will remain on the outside of “normal” construction radar.
Q. Can bales be used for the attic insulation? Is it cost effective or too heavy? Is there a better attic solution for green building?
A. Bales can be used as ceiling insulation; however, I don’t think it’s worth it. One would have to increase the framing significantly to handle the additional weight loads of the bales and there are many natural insulation materials that are light weight and better suited to overhead installations. For example, cotton batts, wool insulation, cellulose, and even formaldehyde free/sealed batt fiberglass.
Q. What would it take to retrofit traditionally build wood frame homes? Is it feasible?
A. Yes it is feasible and something that is done every year. The biggest changes that need to be made are as follows: 1. You need to extend the foundation to support the new bales as most retrofits happen to the exterior of the existing home’s footprint so as not to shrink the square footage of the home. 2. Roof overhangs need to be extended to protect the new walls. Windows and doors should be moved to the exterior plane of the wall to prevent water from settling onto the window sills and infiltrating the wall system. Depending on the original home’s siding and framing, there may be additional changes necessary to accommodate the retrofit including moving electrical and plumbing installations (not a bad idea if the house is very old anyway), and changing framing layouts to better serve the home (potential for moving windows and doors or increases their size). These items fall under the “while we’re in there” category. The original siding may also need to be removed to create a better bond/attachment between the new bale wall and the existing structure. It sounds like a lot of work and it is; however, the end result is well worth the effort in most cases. Again, the quality of the current construction should always be taken into account when performing a retrofit, no matter what material is used in the new construction.
Q. Do people have to give anything up living in a straw bale house? [example: comfort, design, size]
A. Absolutely not. Straw bale homes are everything a conventional home is and more. You can design any style home and live with all the comforts of a conventional home. The difference? You live in a healthy home built of natural materials that will save you thousands of dollars on your heating and cooling bills. Furthermore, the homes are super sound proof, fire resistant, and down right beautiful. Here are some photos to give you an idea of what I mean.
Q. I have heard that straw bale houses are so insulated, they can get enough heat from occupants and appliances that they hardly ever need to run their furnace in winter. From your experience, is this true? How often will you have to run the heat/air?
A. I think this is a bit of an exaggeration personally. They are super efficient, yes, but they do still need a heat source. In general, occupants find that they save about 75% on their heating and cooling bills. That’s not exactly heating the house with body heat and appliances, but it is a huge improvement over their conventional counterparts.
Q. What is the best exterior plaster to use in a semi rainy location in the Midwest or eastern US? [not Seattle WA rainy, but Midwest rainy.]
A. I believe the best exterior plaster to use, hands down, is lime plaster. This is true for all climates in my opinion. Lime plaster is natural, very durable, flexible, breathable, fairly easy to work with, beautiful, and hygroscopic (helps mediate moisture in the air and keep the bales dry). There are different types of lime to choose from. My favorite is Natural Hydraulic Lime as I think it is the best quality lime available for plaster in today’s market. Furthermore, it has been used for generations and thus has a long track record of success. You can learn more about using lime plaster here.
Q. Must you have overhangs? Is it ok for exteriors to get wet from blowing rain or do they have to be kept dry?
A. Overhangs are important for any style home and are particularly important on bale homes. Although walls can certainly handle rain hitting them, a continuous driving rain would prve problematic for most bale homes. In fact, that is true for any home of any construction type. Keeping rain off of the walls is a great idea. I typically suggest a minimum of 2′ overhangs, but 3′ are even better. With two story structures, I suggest a first story roof line or trellis to help protect the first story walls.