There are some researchers at the University of Bath in the United Kingdom who are testing straw bales and hemp, clad in panels, as a way to build homes. They call it a BaleHaus.

Straw has become increasingly popular to build with and at the Sustainable Sources Strawbale Building Registry they keep track of the number of straw bale structures that have been built across the globe. Of course these numbers are only from people who voluntarily list their project so Sustainable Sources claims the actual numbers could easily be greater by a factor of 10 or more.

It appears the place with the greatest number of straw bale structures that are registered is the United States with 642. China is right behind with 597, Canada has 76 registered, Australia 28 registered, and Mexico has 14. The United Kingdom has six registered putting it in eighth place.

Within the United States, the state with the highest number of strawbale structures registered is California with 118. They are followed by Colorado with 70, Arizona with 51, and then Texas with 47.

According to the article in Science Daily that was reporting on the BaleHaus above, straw is an excellent green building product. One of the main reasons for that is because it can be grown locally. The article also revealed that buildings made from straw can be seen as having a zero, or even a negative carbon footprint. The high insulating properties from straw bales mean that, depending upon your climate, you may need little to no conventional heating.

The straw used in the bales can come from many different kinds of plants. Two of the homes built in Texas used wheat straw, and another one used rice straw.

The project in Bath is going to use straw bales and hemp and will use

Photo Courtesy of the University of Bath

what’s called a “modcell” process. Basically they have prefabricated wooden boxes and then stacked the straw bales inside these panels. The finished covering will be a breathable lime-based system.

Professor Pete Walker, director of the BRE Centre in Innovative Construction Materials at the University of Bath said:

Up to this point straw bales have not really been seen as a credible building material by much of the industry, even though straw has always been used in building for centuries, and straw bales have been used for about 100 years.

He went on to point out that because straw bales are an agricultural byproduct then not only is it a material that would otherwise be wasted but at the same time it’s a sustainable material, or one that can be re-grown. He also said that by getting the straw from farms that are local to the construction site, transport costs are greatly decreased which in turn helps to reduce the total carbon footprint of the building.

This particular effort in Bath is going to be monitored for a year to assess the insulating properties it has, the humidity levels, the air-tightness, and the sound insulation qualities. There will be sensors put into the walls to monitor all of those things. There will be other technologies used to simulate the heat and moisture generated by people.

While some people have claimed that using straw bales is a fire hazard there is apparently some evidence quite to the contrary. An insurance agent who has been writing policies for strawbale homes in Virginia claims that because the bale is packed so tightly there’s no way for air to get into it. So while it isn’t fire proof it is hard to burn. He claims that on a scale of one to 10, with one being a home that is completely fireproof, a strawbale home would be a three or four, while most homes are closer to 10s.

However, not every insurance company is actually sold on the fire safety of straw bale construction. Typically, for those companies that have not had the need to write any policies you’ll find a greater resistance to getting insurance for them. Other companies however have been writing policies for strawbale homes for some time, and don’t see any problems with insuring them. One agent with Farm Bureau insurance in Arizona claims they don’t even have any special criteria for strawbale houses, and there’s nothing on the insurance application that says the homes are strawbale.

Here’s a link to some pages that feature a home in Texas, with some pictures. Here’s another one that was completed in 1998 for about $90 per square foot. Finally, here’s a link to several others.

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