Tech Tues: (Un) Straw bale
[photo via Treehugger & Ted Owens]
Straw bale homes have been receiving a lot of attention. With promises of high insulation values, low energy cost, and the comfort of using renewable materials. All of this positive promotion is good, it highlighting an alternative method of construction, but I also feel a need to point out the negatives.
In order for an “alternative method” to change the industry it needs to be practical and cost effective. Straw bale building doesn’t meet any of those, in my opinion. In order to prove my point, or for you to see my point of view, we need to go over the basics.
Straw bale construction is divided into two types. The first, and not as commonly used, “structural bales”. The bales are used for the exterior walls and carry the loads of the roof. A typical bale can hold up to 600 lbs/lineal foot. This is not enough to support an additional level. Limiting this type of construction to a single level. However there are advancements being made so structural bails can handle loads comparable to concrete.
[photo via Treehugger & Tedd Owens]
The most common, and second type, of straw bale construction is “infill”. Simply put the bales are used as insulation between a double framed wall. The outer most wall is constructed as a post and beam and is required to carry all the structural loads. We are talking about 4″x4″ wood post spaced 4′-0″ on center connected to doubled up headers using metal brackets. That covers the structure, now the aesthetics. To finish a straw bale wall you have to apply a thick plaster or stucco [youtube vid] like finish to BOTH sides of the bales. This plaster or stucco finish is made up of either cement, lime, or earth and sand. This encapsulates the bales adding strength, water resistance, and even fire resistant.
How did I come up with my decision to not accept straw bale construction as a affective alternative? It is going to be easier for me to list them out:
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Straw bales cannot contain moisture and easily mold.
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Bales are not compressed, so over time they will settle.
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Constantly repairing the plaster/stucco finish from the settling
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Unrepaired plaster/stucco result in water damage and increased chance of mold growth.
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Amount of lumber needed to build the structure. Double wall construction.
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Walls are 16 inches thick. Windows need to be set to the exterior face of the walls. This creates an extra deep sill.
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The wall thickness decreases finished square footage and requires a larger foot print.
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Plaster/stucco finish needs to be on both sides of the walls. Not easily repaired, nor for hanging a picture.
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Solid exterior walls makes it difficult to run required electrical fixtures.
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Unless you are a DIY’er the plaster/stucco finish is very labor intensive.
Straw bales are fairly easy to come by making them a very renewable resource. However, using them still requires the same amount of lumber to build the structure. Since the skin (plaster/stucco) is applied directly to the bales and post and beams there is no need to add brick or siding. As I stated above, the plaster/stucco finish will require a fair to high amount of maintenance.
I believe my analysis and criticisms are accurate. I also believe it is what will keep straw bale construction from becoming more widely accepted. What am I missing or where did I go wrong? That is the benefit of us having this discussion, it will allow for all of us to learn more.
[please visit Ted Owens website and the other links for more information about straw bale construction]
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4 opinions for Tech Tues: (Un) Straw bale
Dustin
Mar 26, 2007 at 5:32 pm
Just a quick rebuttal to your list…
Straw bales cannot contain moisture and easily mold.
- Strawbales can contain moisture, and in fact do. where you run into problems is if you have too much moisture which is only occurs if you are using rebar to stabilize your bales causing warm air to condense on the metal or have improperly covered your bales allowing excess water to get in.
Bales are not compressed, so over time they will settle.
- Again if you are improperly erecting your bales , yes they would settle but so does every house
Constantly repairing the plaster/stucco finish from the settling
- Again every house settles and this same repair needs to be done
Unrepaired plaster/stucco result in water damage and increased chance of mold growth.
-Also true, but not repairing any kind of house is going to lead to damage or continued deterioration
Amount of lumber needed to build the structure. Double wall construction.
-Actually Strawbale houses use less wood unless you are framing a wall on the exterior and the interior, and if you are doing that… then why are you building a strawbale house since this step is not necessary.
Walls are 16 inches thick. Windows need to be set to the exterior face of the walls. This creates an extra deep sill.
-Not really sure how this is a con since a lot of people get windows designed with this extra deep sill intentionally in a conventional home.
The wall thickness decreases finished square footage and requires a larger foot print.
-This is true but if you are dealing with limited space maybe strawbale isn’t an option for you… not really a con against the building method since that extra thickness increases your insulation value
Plaster/stucco finish needs to be on both sides of the walls. Not easily repaired, nor for hanging a picture.
Solid exterior walls makes it difficult to run required electrical fixtures.
- Both of these cons are the same and it requires planning ahead of time to know where you are going to put things like electrical, but this is the same in a conventional house.. I don’t know anybody who finishes a wall using studs and drywall and then bashes a hole in it to put in electrical appliances later
Unless you are a DIY’er the plaster/stucco finish is very labor intensive.
-Also true but that is the nice thing about strawbale is it is very DIY’er friendly. Everything about building a home is labor intensive, if you don’t like labor… simply put don’t build a house yourself.
I think that covers it… there certainly are cons to building with strawbale but the ones listed here are superficial and not really cons so much as a dislike in design in my opinion.
Adam
Mar 26, 2007 at 9:28 pm
Dustin,
Thank you for your valuable time and detailed response to the post. I appreciate your opinion and wonder if you have built a straw bale home of your own?
dave
May 21, 2007 at 1:59 pm
Strawbale homes have elevated to being listed on http://www.ListedGreen.com ( Listed Green ). A worldwide internet platform for green homes. Maybe strawbale homes can eventually be built on a development level and build communities instead of one-by-one.
Dustin Reimer
May 21, 2007 at 2:12 pm
This guy already has started building them on the communitie level in Oregon and he really knows his stuff
http://www.thestrawbalehouse.blogspot.com/
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