Straw Bale Q & A

Written by Andrew Morrison

Question markI 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, are 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 in our How-To Instructional Series. It’s over 10.5 hours of professional instruction for only $40! You get a FREE set of the Mountain View Cabin construction plans with every order too!

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 prove 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.

A straw bale Q&A is always a good idea; however, the best way to learn is hands on. Join us at one of our 7-day workshops and you’ll see what I mean. It’s a TON OF FUN and you’ll walk away with the confidence to build your own straw bale home, CLICK HERE to learn more about this year’s dates and locations. If you’re not quite ready for the hands-on experience, you can learn a boat load in our instruction video series too. It’s only $40 and contains over 10.5 hours of professional instruction on foundations, framing, baling (load bearing and post and beam), and plaster. Get it delivered instantly to your inbox by clicking HERE.

6 Responses

  1. On the Tiny House email it was mentioned that straw bale homes are more resistant to high winds events such as tornados. I live in Oklahoma. There WILL be tornados nearby this weekend. (High risk by the weather folks)

    I love the idea of straw bale homes, but I had never heard about them being more resistant to high wind events. Details for straw bale construction to make a home more resistant to high winds would be wonderful. Verification of these claims by that university in Texas that tests construction methods and materials for high wind resistance would be exceptionally wonderful. (they shoot 2×4’s with a cannon at things like walls, windows, etc. to simulate flying debris hitting houses in tornados or hurricanes.)

  2. Hi David. I believe there has been some of this very testing done; however, I have not found the data results anywhere, so perhaps I am mistaken. Do you know which university in Texas does the testing? I would be interested in contacting them to see if they would do a study for bale walls.

  3. Hi David, I found the Texas Tech University Wind Science and Engineering Research Center. They are the ones that do the testing you had mentioned. I have written to them and hope to get a ball rolling towards either finding the existing study or studies and/or initiating a new study. Thanks for the tip and nudge!

  4. Precisely how a straw bale home is constructed is probably going to affect how it performs in high wind events. The thickness of the walls are a plus – better to slow down fast moving projectiles. Normally, straw walls are tied down and compressed in some way, and have reinforcing (metal or wood or whatever) both horizontally and vertically. Being tied down to the foundation is a plus. Stick built homes built to high wind standards need a fair amount of metal hardware in key spots to tie the whole structure to the foundation.

    I wonder if a layer of metal mesh or metal lathe would help the walls be more tornado resistant?

    I believe it IS possible to build a significantly better wind resistant home than what is usually available. A friend’s newly built high wind design home was in the middle of an F4 tornado’s half mile wide damage path near Perry, Oklahoma, on May 3, 1999(?) (same day as the big F5 tornado hit OKC) Her home was not destroyed! The carport was ripped off and the tool shed outside never was found again, but the house survived intact with minimal damage. The house was built with additional lumber, thicker sheathing, and metal tie down hardware. It can be done.

  5. @ David Tyler, National Geographic magazine several years ago had a 2 or 3 page short story about earthquake resistant housing designs. They had several designs for various climates and cultures. One of the designs was a straw bale home, as I recall. If I remember correctly, it had concrete base plate connected with concrete support columns which were connected with a concrete top plate. The straw bales were used as filler in a concrete box. The idea was to make the wall rigid enough to move as a single unit and not as a bunch of straw building blocks all moving separately during a quake.

    Also, the current “HOMES” issue of Fine Homebuilding has several articles of interest. One of the homes highlighted is a hybrid straw bale home (walls with lots of windows are conventionally framed.) They show how 14 inch wide wood I-beams are used for the post and beam frame that holds the roof up.
    Another article is about “resilient” housing which can protect its occupants during severe weather of various types, whether that be high wind events or weather events that knock out electric power for weeks on end even up north in the winter.
    Another article talks about how far behind the USA is in not improving “building science”. The 1970’s saw lots of effort to improve the efficiency of homes. Much of that effort stopped in the 1980’s with the election of Reagan. We’re just now picking up the ball again. (This straw bale web site would be part of that.) There is still much we do not know about moisture condensing where it shouldn’t where it causes rot and mold.

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