by Andrew Morrison
Some time ago I introduced you to the idea of building a tiny house with a not so tiny material: straw bales (http://tinyhouseblog.com/straw-bale/tiny-straw-bale-cabins/). The idea seemed strange at first glance to some of you; however, I have heard that many of you have since embraced it. Straw bales are obviously not an option for someone wanting to build on a trailer as the weight of a plastered straw bale wall assembly is far too heavy. For a home built on a fixed foundation, however, straw bale construction is a fantastic option. Let’s take a look below at the advantages of this construction technology:
- Straw bales are extremely energy efficient. For home owners building larger homes, the average savings tend to be around 75% over the heating and cooling costs of a conventional home. Several of our friends who live in straw bale houses report that they barely use their heating system in the winter because the home is so efficient. What’s more, they don’t even have air conditioning units installed in their homes, which stay perfectly comfortable all summer long in temperatures that reach daily highs of 100 degrees F or more. In terms of tiny straw bale houses, a friend of ours built two straw bale cabins (300SF each) and noted that their heating system only comes on once per day. That is significant when you consider that a typical heater will fire several times an hour to keep a conventionally built tiny home warm.
- Straw bale homes are extremely sound proof. This quality is a particular benefit for a tiny house in a busy area. Small houses don’t provide extra square footage to reduce the infiltration of external noises. For example, in a large home, it is common to place bedrooms and other quiet spaces towards the back of the house, away from road noise. What’s more, closets, bathrooms and other “dead space” can be used to further buffer the quiet zones in a house from the impacts of external noise. Tiny houses simply don’t have the “dead space” to help create those buffers. Every inch of living space is needed for actually living, so no matter where you place your bedroom, there won’t be much to quiet the outside world. Thick straw bale walls, on the other hand, can provide a dramatic reduction in external noise in the interior space. In fact, it’s not uncommon to have difficulty hearing someone on the other side of an unplastered straw bale wall during construction. Once plastered, the elimination of sound is even more impressive. In some cases, straw bale landscape walls are used to buffer entire properties from highway noise, so the impacts of having a tiny home built with four straw bale walls is quite impressive.
- It’s true that thick straw bale walls take up space; however, they also offer storage options and creative architectural design elements in your home. Because the walls are so thick, the window wells are very deep and provide a great place to display items in your home. You can also carve into the walls in specific areas to inset cabinetry or even an eating or sleeping nook. The ability to carve and shape the walls means that there is a lot of room for creativity in your design in ways that conventional construction simply cannot offer. Recessing cabinetry and other storage elements into the walls means that floor space is not actually impacted in those areas, which is a great advantage in a tiny home.
- Although there are other advantages to building with straw bales such as the beauty of the plastered bale walls themselves, their fire resistance (3 times as fire resistant as conventional construction per ASTM testing), their superior strength in high winds, and others, I want to focus on one more of the advantages in particular: the natural material itself. Because tiny houses are so small, any and all toxic building materials that off-gas, do so into that concentrated, tiny space. This means that your foam insulation, glues, formaldehyde, paint, and many other standard building materials will fill a tiny space with the same level of off-gassing that is typically seen in larger homes; however, those larger homes have more interior volume over which to disperse those VOCs and other toxic materials. After all, a framed and painted, 10’ tall wall will off-gas the same amount of toxic material in a tiny home as it would in a large home; however, 100 to 200 SF of interior space versus 2000 SF will surely concentrate the effects of that off-gassing. In comparison, the elements of a straw bale wall assembly: the framing members (if properly sourced), the bales, the plaster, and the plaster color, are all completely non toxic and natural. There simply is no toxic off-gassing from this wall assembly, which is a huge advantage for us tiny housers.
No matter what advantage draws you towards building your tiny house with straw bales, the results will be efficient, healthy, strong, quiet, and beautiful. For those interested in building with bales, I invite you to visit www.StrawBale.com to learn more about how the process works and how it can fit into your plans to build your perfect tiny dream home. We offer a totally free 16 day straw bale ecourse as well to get you started on learning about straw bale right away. I have been teaching people how to build with bales for many years and I can tell you that those who have followed through and built their own homes all LOVE them.
In hopes that you will join me at a hands-on workshop this coming year, Gabriella and I have created a coupon code, exclusive to our tiny house friends here on TinyHouseBlog, that will save you $100 on your registration. To take advantage of the discount, simply type the following into the discount field during the checkout process: TINY STRAW. The discount expires December 21. Our workshops are a blast from start to finish and you will not only learn a ton about building with bales, but also have a week of fun, connection, and inspiration.
Sorry, the Oregon location is already full. The Arizona workshop only has 2 spots left and Idaho just 5. The rest of the locations (Australia, Vermont, Nebraska, and Texas) still have a bit more room in them. Here is the link to the workshops themselves: http://strawbale.com/store/category/workshops/ I hope you can join us. Happy baling and stay tiny my friends.
The best strawbale house I ever saw was posted several years ago by a man who had done all of the work himself. There were ceramic tile floors and casement windows that were diamond pane. The pictures only showed the kitchen because he was still working on the place. I never saw any pictures after that and wondered how he finished off the rest of the house. It was truly something with its marble counter tops and all. It really proved that a strawbale house could be just as elegant as anything else out there on the market.
I see one huge problem with straw bales houses; mice.
Mice can’t get into the walls because of the plaster or stucco. They would only be able to get in a damaged wall, same as any type of house.
Hi Fred. Although a common concern, mice and other pests are actually not a problem at all. Because the walls are covered in roughly 1.5″ of lime plaster, and the bales are incredibly dense, there is no space for mice to make a home. In a stack of bales in a barn, there are a lot of soft gaps and spaces for the mice to move; however, those are totally eliminated in a bale wall assembly.
Good stuff. Any info on how this conforms (or doesn’t) to most US building codes?
Hi Mike. The good news is that there is a full code section on straw bale construction in the 2015 IRC. That is a nationwide building code and makes getting approvals very easy.
That great to hear. Is there a place online to access the full building codes? I can never seem to find them…
http://www.iccsafe.org/content/pages/freeresources.aspx?usertoken={token}&Site=icc
Thank you!
Seems somewhat limited; my state isn’t up there and they also don’t seem current.
YMMV. Try the international codes even though they only go to 2012. Some states don’t have their own version.
While I like straw bale and all, I do not understand the fascination with it’s insulating qualities. Straw is only ~R-1.5 per inch. So of course it stands to reason that an 18″ bale would have good insulation, being somewhere around R-27. But what would happen if you built an 18″ wood frame wall and filled it with cellulose loose fill (AKA shredded recycled newspaper)? You’d get something more on the order of R-3.5 per inch and an R-63 wall. Of course, you still have the opportunities to build the cute little cutouts and storage spaces.
So why do straw bales get so much love?
I built my Straw Bale Home in 2011 and I still can’t believe how energy efficient it has been.
I just came back into my house from 40 degrees outside and in felt like a furnace was going. I open all the curtains in the day and let all the sunshine inside.
I have no furnace and only use the wood stove a minimal amount in the winter even when it goes below freezing the wood stove does the job.
I also enjoy the sound proof qualities and often cannot hear a car in my driveway until my dog barks.
Many of times I did not know it had been raining until I opened the door.
That’s fine and I can appreciate you promoting the qualities as stated in the article.
But how is straw bale better on a technical scientific level than the same wall thickness of wood framed cellulose filled?
Because if you built an 18″ wall with wood frame you would be talking 3 to 4 times the material (wood, insulation etc), and 3-4 times the cost…
Where, Kansas or Alaska? In Kansas, I’d say strawbale is going to be cheaper, hands down. You still need to buy some of the materials for the stucco coating (unless you have a lime quarry in your backyard). In places where straw is less plentiful, it may or may not be the cheaper option.
An 18″ wood framed wall would be built with two 2×4 walls. Since homes are normally built with 2×6 walls, we’re looking at 1.5 times the amount of wood, not 3x or 4x. Besides, I don’t need 18″ to match the R-27 of a strawbale wall, I only need 8″. Again, going from 5.5″ to 8″ thick is about 1.5x. Where am I missing the jump to 3x or 4x?
Strawbale construction allows for a very free form design if you are building the type of house that put the wire over the bales. Free flowing lines, smooth surfaces, arches, and non-linear walls all are relatively easy to make. Blowing insulation into a regular wall means you first must have a regular wall and limits you to flat surfaces and standard stick built shapes.
It’s not just about the insulation, it’s also about the freedom of design.
Sure but to curve the strawbale wall, you’d ideally use a chainsaw to taper the edges so there’s no large gaps.
“Standard stick built shapes” makes me chuckle. There’s a whole ton of stuff you can do with lumber and plywood that just isn’t normally done. Well OK, it is, but only on multi-million dollar homes. For a tiny home, there’s no reason you can’t use those same effects.
If I’m building an 18″ thick framed wall, I’ll likely be building two 2×4 walls. In that case, I can be as random and non-linear as needed. I could pull the wall down to 12″ or 8″ total thickness if I want, create recesses at will. But for the R-27 I could get from a strawbale, I might as well build a 2×8 wall or build my 2-2×4 walls 8″ apart for the entirety. With a double stud wall, I get sound attenuation and thermal breaks.
The biggest confusion of straw bale construction R-value is that the straw itself is the only measure used in the per-inch calculations. The entire wall assembly has to be considered because it acts as one with the plaster being fully embedded into the straw, not sitting on top of it like in conventional building materials. The combination of the straw’s Rvalue, the plaster’s thermal mass, the lack of thermal bridging of framing materials, and other factors makes a straw bale wall roughly 3 times as energy efficient as a conventional wall. Couple that efficiency with the use of a natural, waste material that makes up the bulk of the construction, and you get a healthy, relatively quick and inexpensive construction process. There are certainly other ways to reach the energy efficiency provided by straw bale wall assemblies, but straw bale has several other factors that help it “get all the love” as compared with other means. It may not be for everyone, and that’s okay.
I’ve got a few years under my belt working as an energy efficiency consultant for local power utilities. Plaster has an R-value of between 0.3 and 0.5 R/in. Since strawbale is about 1.45, plaster seems to defeat the insulative properties of straw.
But let’s say you only have 3″ of the outer layer of straw permeated with plaster. In this case your wall (simplified) would calc out to be 3 * 0.5 + 15 * 1.45 = R23.25. Of course, I could add the air layer and other factors but they’re negligible.
What you might have been getting at is the tightness that plaster over straw affords. In my part of the country, standard construction is 7.0 air changes per hour (ACH). This is okay but 3.0 ACH is much better. 0.6 ACH is phenomenal and gets on the level of PassiveHaus standards. Straw bale homes can land in this latter range *IF* the window and door bucks and the transition to the top plate and ceiling are well detailed.
Of course, stick frame houses are reaching this ACH as well, as demonstrated by the aforementioned PassiveHaus.
So perhaps the biggest pro is the use of a waste material? I could start trolling and claim that it would be better used in this day and age to brew biofuel (instead of using actual food like corn) but I think we’d be getting way off topic.
Straw bale construction is certainly an option for small houses, but only if the location is permanent.
A better wall solution is ICF. ICF is a much easier for the DIY builder to use than straw bales. And you would get more useable interior space with ICF if you compare the same outside dimensions of a house built with straw vs. one built with ICF blocks.
Although ICFs can provide a quality wall system, I would disagree that it is a “better solution” than straw bale construction. Your walls would end up slightly thinner (not much mind you); however, they are full of concrete. The production of concrete is one of the most environmentally devastating practices we have in the construction industry. For every pound of Portland cement (the binder in concrete) that is produced, a pound of carbon dioxide is produced in the production process due to the high temperatures at which the material needs to be “cooked.” What’s more, the rigid foam that is used in the ICF is much more toxic than straw and plaster. Be sure to compare all aspects of what makes a wall assembly a “better solution,” not just the apple to apple R Value.
is this legal in California?
I assume it depends on the county/city regulations, but I have seen a couple of straw bale houses in Guinda, California. They even do tours of some at the Hoes Down festival.
Straw bale construction is absolutely legal in California. There are many straw bale houses already there. There is also full approval of straw bale construction in the 2015 version of the International Residential Code (IRC) which is the building code that governs all residential construction in the United States, nationwide.
‘Small Strawbale: Natural Homes, Projects, and Designs’ is a good book written by authors with a lot of experience building with straw bales. They have a non-profit that promotes strawbale building and help people design and build their own.
I like the idea bit what about the straw decomposing as does all organic material do.
In Ontario Canada there are much more generous width limits for straw bale transportation. If you could convince the ministry of transportation that it was a hay wagon and not a house.
Straw needs water and oxygen to decompose. Straw bale walls are densely packed eliminating airflow and protected from water by the stucco finish.