A straw bale house is constructed using straw either as the main structural element or as insulation or both. The buildings are constructed by stacking rows of compact bales of straw on a sturdy foundation before being sealed with a moisture barrier and an outer layer of gypsum. They usually have very thick walls with efficient thermal mass for lower energy bills and year-round comfort.
Straw bale homes are relatively rare, but the practice is gaining momentum thanks to growing sustainable design trends.
Straw is cheap (sometimes free) and the entire process reduces construction waste that can have a negative impact on the environment; Any excess straw or natural plaster on site could, in theory, be used in compost or as ground cover to protect the soil. One paper found that straw buildings save 40% on construction costs compared to traditional homes.
What is the House of Straw Bell
Hay is an agricultural by-product that comes from growing grains such as wheat, oats, and rice – the straw itself is made from the dried stalks of grain plants after the grains have been removed. It has been used for thousands of years as a building material to strengthen clay structures or clay as an inexpensive, renewable resource with good insulation value.
The modern practice of straw thatch building originated in Nebraska during the late 19th century, when early settlers were looking for the fastest method of temporary housing (although straw and reeds were used as building materials in thatch roofing throughout the Middle East for thousands of years before that). Unsurprisingly, the method of construction directly followed the invention of the steam bale engine, which collected straw and packed it into the tight, brick-like bales we see today.
straw construction regulations
Whether or not your state has a building code for straw bale construction depends on the region. Those planning to build a thatched house will need to search the code book for their specific case and check the alternative building department as well as any local or state additions.
In California, for example, thatched straw houses have their own guidelines; They include a minimum bale wall thickness of 13 inches, a maximum of one storey in the case of buildings with load-bearing pallet walls (unless they were designed by a state-licensed civil engineer or architect), and at least 40 other requirements .
In general, a thatched house covered with stucco, drywall, or stucco is equivalent to fire resistance as a timber frame construction.
How to build a thatched house
Basically, there are two ways to build a straw carrier house – bearing and loads. This load-bearing straw house uses straw bales as the primary structural support, making it more reliable in milder climates.
On the other hand, a non-load bearing straw straw house uses another material, such as wood, for its primary support. Bales of straw are then added to form the walls and provide insulation, so it’s often a better choice for unpredictable climates or those with a lot of snow.
Construction begins with the foundation, something as sturdy as a layer of concrete, in which bales of straw are stacked on top of each other to form the walls. A moisture barrier is then applied to the surface of the walls, usually consisting of earthen plasters, cement stucco or gypsum.
The final layer consists of another plaster made of clay, lime or cement to provide thermal mass, which can serve as a top layer or supplement with paint. Oftentimes, the owner decides to use an additional sustainable building element, such as a rammed floor wall, to add texture or complementary details while maintaining the home’s overall eco-friendly appearance.
In addition, small sections of the interior wall may be left unclad and opened with glass or a frame such as a window so that occupants can see what the building is made of inside.
The straw bales are fixed to each other using pegs of wood, bamboo or rebar so that they do not fall off during construction. To keep the house in good condition, it is important to periodically check the plaster layer for cracks and holes to avoid excessive moisture and subsequent mold.
Pros and Cons
Overall, straw is a sustainable material that has a lot of redeemable features when it comes to construction, although it may not be right for everyone or every situation. Take time to consider the risks and rewards (and limitations) while considering a thatched house.
Positives
Renewable materials
Rattan straw houses are environmentally friendly thanks to the main material, straw, being a completely renewable by-product of the agricultural industry.
Hay already has many uses, such as bedding or bedding for animal sheds, and it can be regrowth quickly each year rather than the longer time it takes a tree to mature for wood.
Harvesting lightweight straw also requires less energy than producing and transporting timber—farmers can leave it in the fields to protect the soil from erosion, add organic matter or return nutrients to the soil.
Cost-effective
Not only is thatch less expensive than traditional building materials such as wood, concrete and steel, but thatch house can be less expensive to heat or cool due to its higher insulating factor.
A study published in the Journal of Building Engineering in 2017 conducted a life cycle assessment using a straw wall to investigate energy and environmental performance. The researchers found that while the wall provides adequate thermal insulation under constant winter conditions, the lightness of the structure may be detrimental to unstable summer conditions and overheat in warm climates. Overall, the paper concluded that the use of straw bales in the walls is able to reduce both energy and carbon embodied in the building.
Low fire risk
This may sound far-fetched, but thatched homes don’t actually pose a higher fire risk than traditional homes (once finished, that is). Since the hay bales are tightly packed, there is not much airflow available to start a fire.
According to fire safety tests conducted by the National Research Council of Canada, the thatched straw house was able to handle temperatures of up to 1,850 degrees Fahrenheit for two hours.
Biodegradable
The staple materials for a straw straw house can be returned to the ground at the end of its life. Thatch, natural clay plaster and most other parts of the soil can simply be plowed to decompose naturally.
low embodied energy
Studies in Italy show that embodied energy (the sum of all the energy required to produce a home) is about half that of a conventional home, while CO2-equivalent emissions vary by more than 40%.
Growing and processing straw does not consume a lot of energy outside of the sunlight needed during the growing phase, the blasting process, and the transportation of the bales to the construction site.
Negatives
Allow
Aside from dealing with challenging protocols when planning a thatched house, some states may not even factor it into their building codes; This can make it difficult to obtain a building permit.
Likewise, city officials may find this concept unconventional and uncomfortable to accept a thatched house based on the house’s aesthetics compared to the rest of the area.
moisture
Hay bale homes are more prone to moisture-related issues because thatch will degrade and weaken if it becomes damp, which can quickly become a hazard to residents.
Moisture can come from cracks in grout, plumbing pipes, flash flood damage, or in cases where window sills or joints were not sealed properly. For this reason, climates known to be particularly humid or humid may not be ideal for straw thatch homes.
no studs
Since there is often no wood supporting the structure, thatched straw houses do not have studs in the walls. Hanging anything on the walls, including shelves, cupboards, or even picture frames, would be a much more complex endeavor than in an ordinary home.
pests
Some of the biggest concerns about thatched houses have to do with issues of insects and rodents, although thatch enthusiasts might argue that choosing the right grout and applying it will take care of either. However, depending on where they come from, hay bales may arrive at a construction site that already contains grain-eating pests.
Maintenance work
A layer of grout that keeps thatch dry and safe from mold or mildew doesn’t last forever. Once it begins to deteriorate, it must be replaced, which means that thatch house maintenance is required more often than most other modern homes.
The layer of grout on the exterior ranges from cement grout, which can cause moisture problems when cracking, to clay-based earth grout, which requires regular re-application.