The Beauty of Straw Bale Construction

Straw bale construction is taking a bold leap forward and straw bale homes are being built with an increasing frequency.

| April/May 2001

It wasn't long after the appearance of baling machines in the 1850's that straw and hay bales began to be considered a building material. Historical patents for bale walls date back to the 1880's in Indiana. The first significant use of bales as a building material occurred in the Sandhills of Nebraska, a vast tract of desolate, grass covered hills. An abundance of wild grasses, combined with the lack of timber and good building soils, provided incentives to devise new building techniques using unconventional materials. The oldest bale building on record is a school built in Scott's Bluff County in 1886 or '87. Ultimately, the school was devoured by cattle.

Although many houses built from natural materials are beautiful, the use of such materials does not guarantee beauty. We have seen many straw bale houses that appear no different than any other building. When incorporated into conventional construction, natural materials are subjugated to the same stresses and patterns. Straw bale walls can rapidly become a very insignificant part of the whole house. We once asked a friend how she liked her new house; she responded, "I really wanted a straw bale home, but what I got was a house with straw bales in the walls."

The Right Straw

Bales used for building should be dense and compact, capable of supporting a substantial amount of weight without changing shape or deforming. The strings should be tight, holding the bale securely together. Most importantly, straw used for building should be bright golden-yellow with no signs of discoloration, which indicates moisture damage. Simply put, you should only use bales that have been kept out of the weather.

The R-Value of Straw Bales

R -value means "resistance value," using a rating system for measuring the relative capacity of insulating materials to resist heat transfer.

The first R -value tests of straw bales were conducted on individual bales by Joe McCabe; he achieved results that ranged on average, depending on the size and orientation of the bale, from R-40 to R-50. Later tests conducted on whole wall assemblies of straw bales got lower results: Oak Ridge National Laboratories had R-31.2, while the California Energy Commission adopted a value of R-30 based on testing conducted by Nehemiah Stone. These results were disappointing to those who thought that the tests for wall assemblies, including allowances for losses, would be similar to results for individual bales. However, the same disparity holds true for other materials. For example, 2x6 framed walls that are nominally rated at R-19 only achieved whole-wall ratings of R-12.8 at Oak Ridge, even with properly installed insulation (it often is not). By these terms, straw bale walls compare very impressively.

It's also very important to remember that laboratory tests are conducted under steady state conditions. In the real world, consistent conditions rarely exist for more than a minute or two. The true test of any material is the amount of energy required, over time, to maintain a reasonable level of comfort. Rather than measuring just R-values, it is essential to consider the overall contributions of a wall's thickness and the thermal mass provided by interior and exterior coatings. Together, these provide comfort and thermal performance much greater than R-value alone would indicate.

mother earth news fair 2018 schedule


Next: September 14-16, 2018
Seven Springs, PA

Whether you want to learn how to grow and raise your own food, build your own root cellar, or create a green dream home, come out and learn everything you need to know — and then some!


Subscribe Today - Pay Now & Save 64% Off the Cover Price

Money-Saving Tips in Every Issue!

Mother Earth NewsAt MOTHER EARTH NEWS, we are dedicated to conserving our planet's natural resources while helping you conserve your financial resources. You'll find tips for slashing heating bills, growing fresh, natural produce at home, and more. That's why we want you to save money and trees by subscribing through our earth-friendly automatic renewal savings plan. By paying with a credit card, you save an additional $5 and get 6 issues of MOTHER EARTH NEWS for only $12.95 (USA only).

You may also use the Bill Me option and pay $17.95 for 6 issues.

Canadian Subscribers - Click Here
International Subscribers - Click Here
Canadian subscriptions: 1 year (includes postage & GST).

Facebook Pinterest Instagram YouTube Twitter flipboard