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How much does a straw bale house cost?

The projects featured on the Gallery 2004 - 2009 page range in cost from $ 90.00 per sq. ft. to $ 220.00 per sq. ft. That includes all construction costs, from permitting to painting, but does not include the cost of the property or any sweat equity that the owners or volunteers might have provided.

Generally, the cost of building a straw bale house is about the same as a comparable conventional house but the operating costs, the heating and cooling bills, are much lower in a straw bale house because the insulation value is about twice as good. Over time, and with rising energy costs, that's a difference that is going to really add up. And in saving on your heating and cooling bills, you'll be lowering your green-house gas emissions. It's a win-win!

How much will I save?

When we arrived to plaster a house in Huntsville Ontario, I asked the homeowner why he decided to build a straw bale house. He gave me the most straight-up answer I've ever heard: "Just wanted a warm house D. Just wanted a warm house." He continued to say that the furnace at their old house had turned on every 20 minutes in the winter and it drove him crazy, drove him to build with bales.

After living in their new house for a year, he made a point of telling me that not only had their first winter been warm and quiet but their bill for heat and hot water for the whole year had only been $ 1200.00. He was thrilled.

This home is 2400 sq.ft and houses two families for a total of four adults and two teenagers. They keep their thermostat at 75 and 76 degrees and they don't have, need or want an air-conditioner.

Do you lay your bales on the flat or on edge?

Both. There are pro's and con's to both. At the design stage we decide which is best for that project. The R-value is the same either way. On edge the bale is narrower but the straw is oriented against the direction of heat flow. On the flat the bale is wider but the straw is orientated in the direction of heat flow.

Do the mice get in?

Once plastered, mice will have a hard time finding their way into a bale wall. If they do, the inside of a plastered bale wall is too dense for them to work. There is no room for them to off-load the straw they need to tunnel and nest. It would be like trying to dig your way out of a snow bank from the inside, a snow bank encased in a hard layer of ice.

What is the R-Value of a straw bale wall?

R in this case stands for Resistance so R- Value is a measure of a material's resistance to heat flow. The R-value of a straw bale wall ranges from 30 to 40 which puts it in the class of a super insulated wall and that's all that that really matters. The difference between R 30 and 50 in your walls really isn't that great. As Nehemiah Stone writes in Design of Straw Bale Buildings, "An R-9 wall allows more than twice as much heat to flow through...than does an R-19 wall. An R-33 wall, by contrast, allows less than one third more heat to flow through compared to an R-43 wall." - King and al, Design of Straw Bale Buildings, 2006, pg. 190

Won't a bale home be likely to rot or mold?

Water vapour always want to go an area of high concentration to low concentration. In a house, that's usually from inside to outside. In a bale house, it can do that without collecting and setting the stage for rot or mold because it doesn't get trapped along the way. The plaster skin on the inside is a vapour retarder. It slows the passage of vapour down to the point where the straw can easily absorb and release moisture to the outside. Bale walls deal with vapour by not trying to fight it. They know that water always wins. They know that small amounts are going to get in and so they allow so they alow it a way out. In so doing, they win too. Bale walls are smart and dry as a result.

Where is the dew point in a straw bale wall?

No tests have ever found a dew point in a bale wall. The assumption is that there is so much storage capacity in the bales that moisture is adsorbed or absorbed long before it reaches the critical mass required to actually form water droplets.

Won't they burn or combust?

No, a straw bale wall is actually fire resistant in two ways. First the plaster shields the flames and second the straw is baled too tightly to support combustion. The National Research Council fire test found:

"Bale walls withstood temperatures up to 1,850˚F for two hours." - Fire safety tests, National Research Council of Canada

Frank Tettemer of Living Sol ~ Building & Design, www.livingsol.com , will be using a plastered straw bale wall as the separation wall between two units in a straw bale duplex he is currently building in center-city Pembroke, Ontario, to be completed in 2010.

This wall between the two adjoining residencies, must have a fire-resistance rating of not less than 1 hour, according to the Ontario Building Code part 9.10.9.11.(1).

When barns burn due spontaneous combustion, that's hay not straw. It's a mortal sin in the bale building world to confuse the two. But I'll admit I didn't know the difference until I became a builder (grew up in a city...sigh).

What's the difference between hay and straw?

They both start out the same, as grass growing in the field but hay is cut and baled when the plant is green and full of moisture and straw is left to mature and dry in the field. Hay is food for animals and straw is bedding for animals. Straw is the stalk that is left over after the grain has been harvested. Bales of hay have a high moisture content and are susceptible to rot, mold and spontaneous combustion as a result. Bales of straw have a low moisture content and are not susceptible to mold and spontaneous combustion unless you soak them in water or gas.

Bale builders say, "Hay is for horses. Straw is for houses. "