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Straw bale walls explained

Straw bale insulation has been used in the US and parts of Europe extensively. Straw is a by-product in wheat/ oat/ barley/ rye/ rice farming. After the chaff and grain have been removed at harvest, the straw stem is left over. The straw stem is then bundled into a ball or block and used for livestock bedding, fuel, gardening or our case- insulation. Strawbales are a great natural insulation material that is renewable and sustainable.


Living in a straw bale home:

Straw bale houses are super-insulated, usually far surpassing the legal requirements for insulation and keeping you super warm in winter. The great thing about the thick straw bale walls is that every window is a potential window seat, getting you closer to the outside and having seating built into your home. The clay plaster (mixture of clay, sand and water) in combination with the straw bales add character and give the entire home a natural feel. The cost of straw bales can vary quite a lot depending on where you are, how accessible it is in that area and the potential transport cost. Straw bale homes do come under the 'Alternative Solutions' in the building code in NZ.

Types of straw bale construction:

There are two options in straw bale construction:

  • one is where the straw bale act as the structural wall

  • one is where there is a standard structural frame and the straw is used as the insulation material only (also called infill).

The biggest worry for builders is to ensure that the straw bales stay dry before, during and after installation; as a wet straw bale will likely start to compost. To protect the straw bales from the moisture in the environment, rain and snow a clay plaster is usually applied. Other cladding options are also possible.


Advantages of straw bale insulation:

  • Superior insulation value compared to other products, keeping your heating costs lower

  • A natural and renewable product that can be recycled or used as compost

  • The thick walls of straw bale homes add character. Walls of the same thickness of other construction methods are a lot more  expensive to construct

  • Due to the thickness of the walls window seats are easily achievable

  • Walls can be carved with a chainsaw or knife, which makes it possible to create funnily shaped walls and integrated shelves

  • Straw bale homes are very fire retardant due to the denseness of the material- this runs contrary to logic but is true


Disadvantages of straw bale insulation:

  • The thick walls mean losing floor space either inside the house or outside the house

  • It is vital that straw is kept dry so roof overhangs are highly recommended but might not fit the visual appeal of your home

  • It is difficult to predict the wall costs as it depends on availability and transportation costs.

Image by Mihály Köles
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