Powdermill Nature Reserve

Straw Bale Insulation

tomsFully cognizant of its responsibilities for environmental stewardship, Powdermill underwent a significant expansion and upgrade including technologies that are energy efficient, are derived from renewable resources, and that effectively manage wastewater. The building itself serves as an educational exhibit of environmentally sensitive design and construction.

One very interesting and important component of the building is the Straw Bale Wall.

A Brief History 

When most of us hear about walls made of straw we have visions of three small pigs and one angry wolf, but straw bale housing is not a new concept in building. After centuries of use in indigenous cultures, straw bale construction began gaining popularity in the 1890s in areas of the United States that had few lumber resources, but plenty of residual material from the farming of grain crops—mainly the plains states.

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After the grain crop was harvested, the remaining straw was baled and stacked like bricks, pinned through with metal or wooden stakes, and sometimes sewn together for strength. Windows and doors were cut out, and the walls were covered with a layer of stucco. The roof was attached to a top plate laid over the final row of bales and secured to the foundation with metal rods or straps. Windows and doors were installed, and the house was ready! Often, the walls of a house could be raised in a single day. The Sturtz Ranch in Stapleton, Nebraska, was built in 1905 by local craftsmen and was inhabited by the same family until 1998. The house still stands.

Why Here? Why Now? 

Pennsylvania certainly has no shortage of lumber, so why are we using bales here? The hollow, air-trapping nature of the plant stalks combined with the compact nature of bales provides a beneficial side effect: insulation. Our all-natural, home-grown insulation reduces the amount of energy needed not only to heat our building, but to create it. The traditional pink insulation requires high amounts of energy to be produced, shipped, and sold. Our bales do the same job and do it just as well, but without the high energy costs.

wallWe used switch grass, a common cover crop for hunting preserves in the area, which has to be cleared periodically. The crop is sustainable, and baling reduces the chance the crop will be burned—which releases carbon dioxide into the environment. Our insulation was grown and donated by Tom Stickle of Monona Farms, Ligonier, less than 20 miles away!

And what about the bugs? Many people wonder about the safety of using bales in their homes. However, the compressed bales covered with stucco allow very little oxygen into the walls. Critters find it hard to breathe or nest within the sealed bale walls.

The main concern is moisture, as wet bales can mold and decay over time. The best defense is to keep the bales dry before installation and to seal walls completely.

The Process 

sealedIt all started with local farmer Tom Stickle planting switch grass (first picture at top). The grass spent the summer providing cover for small game, then died in early fall. The grass was mown and baled, then placed in the barn to dry. The walls of the expanded nature center headquarters were prepared using traditional building techniques (second picture). Bales were stacked within the exterior wall frame (third picture). The bales are protected by a layer of stucco, and the finished wall is covered with decorative wood (fourth picture).