Home Improvement

At the end of the 19th century, people living in the Sandhills region of northwestern Nebraska were faced with a challenge. The area was covered with sand dunes and had no trees for building. Moreover, there were no nearby railway stations to bring in building materials, and the little fertile soil available was better suited for growing crops.

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Photo courtesy StrawBale.com
A modern straw bale home before plaster is applied.
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Perhaps one of the settlers was familiar with the New England technique of using stacked hay bales to insulate blocks of ice, or maybe someone was inspired by the recently invented mechanical baler that produced bundles of straw. In the late 1890s, the settlers began constructing houses, schools, and churches using straw bales. By stacking one bale on top of another, they created square or rectangular one-story buildings with a simple, sloping roof.

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Initially, these buildings were not intended to be permanent, and many were not. One of the earliest recorded straw bale structures was a one-room schoolhouse constructed in 1896 or 1897, which cows ate in 1902 because the walls were not plastered. However, once the settlers began plastering the walls, they discovered that these temporary structures could keep them cool in the summer and warm in the winter. The houses could withstand the high winds of the Nebraska prairie, and they were also quiet. One woman, whose family lived in a straw bale house, recalled her parents playing cards while a tornado raged outside [source: Hammett].

Straw bale construction in Nebraska declined around World War II as cement became more popular. Today, we tend to think of the story of the three little pigs, one of whom built his house with straw, only to have the big, bad wolf blow it down. However, had the pig had access to a baler and some plaster, his home would have been sturdy.

A straw bale house can use straw bales as insulation or as the primary building material. The walls are then finished with plaster. This type of construction is gaining popularity as a natural building method. In 2001, a British company estimated that around 1,000 new straw bale structures were built every year worldwide [source: Amazon Nails].

What is driving the interest in straw bale homes? What advantages do they offer? Isn’t it dangerous to live in a house made of straw? We’ll explore the benefits of straw bale construction on the following page.

Advantages of Straw Bale Houses

With the cost of lumber on the rise and its availability decreasing, straw has emerged as a renewable resource that is easily accessible as a byproduct of growing grains. Most straw goes to waste, but it can be effectively used as a building material. In the United States alone, 200 million tons of straw is unused every year [source: U.S. Department of Energy]. Straw is available in most parts of the country, which reduces transportation costs of construction. By using straw bale houses, the construction industry can reduce the production of greenhouse gases by over 50 percent [source: Amazon Nails].

Although straw is cheaper than traditional building materials like brick or lumber, constructing a straw bale home usually costs the same as a conventional home because the wall budget is only 10 to 15 percent of the total building budget [source: Magwood, Mack, Therrien]. However, cost savings can be achieved by using straw bale raising parties. These are similar to barn raising parties, where a group of people stack bales like building blocks. Building a straw bale home requires little experience, and it can be done quickly. Many resources are available online to teach you how to build your own straw bale house, but it’s important to know when to seek the help of a contractor.

The real cost savings of straw bale building are related to energy efficiency. Straw bales, finished with plaster, have a high R-value which measures the insulation resistance of the wall. Straw bale walls provide excellent insulation that can easily keep heat in or out, depending on your needs. A straw bale home can save up to 75 percent on annual heating and cooling costs [source: Morrison, Amazon Nails]. These thick walls also provide excellent soundproofing. Recording studios and homes near busy highways have benefitted from straw bale building.

Straw bale houses may seem like a fire hazard. However, they provide three times the fire resistance of conventional homes [source: Morrison]. The tightly packed bales reduce the chance of combustion because there’s no oxygen within them. The plaster coating of the walls adds an additional fire-resistant seal. Tests conducted by the National Research Council of Canada showed that straw bale walls withstood temperatures up to 1,850 degrees Fahrenheit (1,010 degrees Celsius) for two hours [source: Magwood, Mack, Therrien].

Photo courtesy StrawBale.com
The thick walls of a straw bale home provide good insulation.

Straw, not hay, is the preferred material for building a straw bale home to avoid attracting animals. Straw, when tightly packed and combined with plaster, forms a barrier that is difficult for critters to penetrate. Straw is also a natural, breathable material that doesn’t contain pollens and is free from chemicals found in modern building materials. It usually requires additional nitrates to decompose, whereas hay decomposes naturally and causes the house to rot. Moisture is the main threat to straw bale homes, but this can be addressed using appropriate measures.

The design of a straw bale house should take into consideration natural factors such as the sun, wind, rain, and vegetation. The orientation of the house and window placement should be designed to make the most of these elements. There are two main methods of constructing a straw bale home: post-and-beam infill and load-bearing. Post-and-beam infill is closer to a standard form of construction, making it more acceptable to building officials, lenders, and insurers. Load-bearing construction is preferred by some because it requires less construction skill and uses fewer resources, although it has some design limitations such as being limited to one story and having a maximum wall length of 25 feet in any direction. Windows and doors are also limited to 50 percent of the wall surface area. Local building codes should be consulted to determine which construction method is required for your area.

Photo courtesy StrawBale.com

Straw Bale House Design

Reaping the benefits of a straw bale house involves more than just stacking straw willy-nilly. The home should be designed so that nature aids energy efficiency. Before building, figure out where the sun goes, how the wind blows or if there’s water nearby. Where does the rain go when it falls? Think about how trees, shrubs and other natural barriers could block the wind or a heavy sun. These factors will determine how to best orient the house and design features such as windows.

The straw bale home movement is mainly concentrated in the arid climates of the Southwest United States and Southern California. These locations are suitable for this method as the insulated walls can block excessive heat or cold. While straw bale homes are vulnerable to moisture, they have been built successfully in rainy Pacific Northwest and snowy New England. However, humid areas are not appropriate for this type of construction. The Straw Bale Registry maintains a global database of straw bale structures, with the majority located in the United States and China.

The choice of straw is an important aspect of the design. Straw bales are available in various shapes and sizes, but the most common are two-string bales and three-string bales. These are tied together with wire or twine. The dimensions of these bales, according to the U.S. Department of Energy, are:

Type	Dimensions	Weight
Two-string bale	18 inches by 14 inches by 36 inches	50 pounds to 60 pounds
Three-string bale	23 inches by 16 inches by 42 inches	75 pounds to 80 pounds

You can use an online bale calculator to determine how many bales you need for building. Harvest Homes offers an example of such a calculator.

Dry bales should be purchased from feed stores or farmers. Hand-held moisture meters can be used to check the moisture content of the bales. Up to 20 percent moisture content is considered safe. Golden-colored bales are preferred over lighter-colored ones, as they indicate less moisture. Bales should also be tightly strung to maintain their shape when lifted or dropped.

Straw Bale House Construction

Design choices for a straw bale home are similar to those of conventional home building. A straw bale home can have any type of foundation or roof. Solar-paneled roofs can enhance the energy efficiency and environmental friendliness of a straw bale home. Load-bearing and post-and-beam structures are the two options for construction. A load-bearing home involves laying the foundation and stacking the straw. A roof frame is then placed on top of the straw, and the roof is assembled. In contrast, all the structural elements, including the foundation, frame, and roof, are put in place before filling the gaps between the posts with straw bale in a post-and-beam straw bale home.

Photo courtesy StrawBale.com
A toe-up

When building a straw bale house, it is important to keep the bales elevated off the ground to prevent them from absorbing moisture. This can be achieved by using toe-ups, which are platforms made of lumber and gravel attached to the concrete foundation. Nails or pins are hammered into the toe-ups, and the bales are then placed onto them to anchor them. Once the first layer of bales is in place, the rest can be stacked like blocks, with windows and doors inserted into the straw bales using wooden frames. Cutting, notching, and retying bales may be necessary to achieve the desired size and shape, and chain saws can be used to create architectural features like niches or cabinets.

After the bales are stacked, they may be supported using steel or bamboo poles or pins and wire mesh. Plastering is the next step, typically using stucco cement, gypsum plasters, earthen plasters, or lime for internal and external surfaces. The plaster should be applied in three coats, with the first worked into the straw. Waterproofing materials should not be used, as the straw needs to ventilate moisture. Breathable paints like lime, silicate, or some latex paints should be used.

Moisture is the biggest challenge when building with straw bales, as it can cause mold and rot. Precautions must be taken from the moment the bales are purchased, including storing them off the ground and under tarps.

Building a Straw Bale Home

When designing and constructing a straw bale home, it’s important to keep water out of the house. The foundation’s toe-ups protect the home from moisture below, while roof designs with overhangs provide protection from above. Windowsills and joints must be well-sealed to prevent liquid dangers from rain or snow. Additionally, using breathable plasters will keep moisture from accumulating in the walls, and maintaining these plasters will prevent cracks from developing.

Photo courtesy StrawBale.com
Before plastering a straw bale home

Photo courtesy StrawBale.com
The final product of a straw bale home

However, building a straw bale home can be challenging due to its newness in the construction world. Building codes may not account for straw bale methods, and conservative banks, lenders, and insurance agents may be hesitant to finance this experimental approach. Therefore, those interested in building a straw bale home may need to work closely with building officials to meet codes and gain financing and insurance. They may also need to hire consultants to help explain the benefits of straw bale building to institutions.

If you’re looking for a straw bale contractor, resources such as “The Last Straw” and the green builders’ database can provide assistance. Additionally, educating potential buyers about the benefits of a well-insulated home can help increase resale value, as little data exists on the resale value of straw bale homes.

Straw Bale Additions and Retrofits

Even if you’re already settled in your home, you can still use straw bales for additions and retrofits.

Photo courtesy StrawBale.com
Straw bale construction

Adding straw bale structures to an existing building involves tying the new addition to the existing structure. The process involves laying each row of straw and placing a sheet of metal mesh called a lath over the bales. The lath is then secured to the frame of the existing house using dowels or landscape pins. When building a straw bale addition with wooden frames, the frames can be attached directly to the existing house’s frames. Plastering the addition is done similarly to straw bale construction.

It’s advisable to consult a contractor to ensure the addition’s exterior matches the existing house. When laying the foundation for the new addition, it’s crucial to consider the bales’ thickness and plaster to ensure the finished addition lines up with the existing building.

Wrapping an existing house in straw can improve energy efficiency. However, the design must prevent moisture from penetrating the walls. Straw bale constructions feature large roof overhangs that protect the walls from rain. Retrofitting may require changing the existing roof, which involves changing its slope and extending it.

When adding bales to the outside of an existing house, windows and doors may require some adjustments. Using 18-inch wide bales can lead to deep wells around windows and doors. Instead, retrofitting with bales on the inside of the house can be done similarly, but it reduces the house’s space by the bales’ width.

Although incorporating straw bale construction may seem expensive, the costs should be weighed against the energy savings achieved over the house’s lifetime. To learn more about straw bale construction, visit the links provided.

The following are sources for information on straw bale building: StrawBale.com, Green Home Building: Strawbale, The California Straw Building Association, and The Last Straw. The sources for information on straw bale building include Amazon Nails, Geiger’s Strawbale Questions and Answers, Hammett’s The Strawbale Search, Keefe’s Straw Bale Design and Site Evaluation, King’s Straw-bale Construction, Magwood’s Expert Advice on Straw Bale Building, Morrison’s 7 Essential Steps to Straw Bale Success, Morrison’s Adding Bales or a Bale Addition to an Existing Home, Morrison’s How to Choose the Right Straw Bales, Morrison’s Recent Radio Show Podcast, Morrison’s Retrofitting a House with Straw Bales, Shepard’s Straw Bale Home Basics, and the U.S. Department of Energy’s House of Straw: Straw Bale Construction Comes of Age.

FAQ

1. What is a straw bale house?

A straw bale house is a type of building construction that uses straw bales as insulation and structural support. The bales are stacked and compressed to form the walls of the house, and then covered with plaster or stucco for weatherproofing. Straw bale houses can be built in a variety of styles and sizes, and are often praised for their energy efficiency and sustainability.

2. How do straw bale houses compare to traditional construction?

Straw bale houses have several advantages over traditional construction methods. They are highly energy efficient, with thick walls that provide excellent insulation. They are also made from a renewable resource, which makes them more sustainable than many other building materials. Additionally, straw bale houses are often less expensive to build than traditional homes, since the materials are inexpensive and the construction process is relatively simple.

3. What are the downsides of building a straw bale house?

While straw bale houses have many benefits, there are also some downsides to consider. One potential issue is moisture damage, since straw is vulnerable to rot and decay if it gets wet. Another concern is fire safety, since straw bales are highly flammable and can quickly ignite if exposed to flames. Additionally, some building codes may not allow straw bale construction, which can make it difficult to get permits for building.

4. How long do straw bale houses last?

If built properly and maintained well, a straw bale house can last for many decades. The plaster or stucco exterior helps protect the straw from moisture and decay, and regular maintenance can prevent damage from pests or weather. Some straw bale houses that were built in the early 20th century are still standing and in use today, which is a testament to their durability.

5. Can straw bale houses be built anywhere?

Straw bale houses can be built in many different climates and locations, but some areas may be better suited for this type of construction than others. In general, straw bale houses do well in dry, arid climates where moisture damage is less of a concern. They may not be as well-suited to humid or wet areas, since the straw can be more vulnerable to decay in those environments.

6. Are straw bale houses a good investment?

Whether or not a straw bale house is a good investment depends on a variety of factors, including the location, the cost of building materials, and the housing market in the area. In general, straw bale houses are less expensive to build than traditional homes, which can make them a good choice for people on a budget. They may also be a good investment in areas where energy-efficient homes are in high demand, since they offer excellent insulation and can help reduce energy costs over time.