joomla analytics

Straw Bale Homes Are Some Of The Most Popular Eco-friendly Structures

Straw bale home design began here in the US with the resourceful Nebraska pioneers of the late 1800s. Having little wood on the plains and facing strong winds, the settlers had to be creative with their home design, using what was at hand. So, they baled their hay and built homes. Finding how well they worked, they later created straw bale houses by plastering over the straw bales.

Previously only appreciated by those Nebraska architects struggling to survive, today, straw bale homes are beautiful, contemporary structures that offer a cache of incentives. Precision Structural Engineering provides residential home engineering, custom home design and more using straw bales in construction. Could there be a straw bale home in your future?

Some Examples of Straw

  • straw2Wheat
  • Rice
  • Rye
  • Barley
  • Oat
  • And similar plants

Because straw is usually locally available it is viewed as a readily available material. Straw bale building is the most popular natural building technique in practice today. When designed for green living, a straw bale home is one of the most comfortable and efficient style of homes available today. Some folks even host old-fashioned bale-raising parties to get their walls up. Could there be one in your future?

 

What is a bale?

A bale is a rectangular compressed block of straw bound by string or wire.

What Makes a Correct Bale?

A bale must meet the following criteria:

  • Dry density of 7.0 pounds per cubic foot
  • Rectangular compressed block of straw with a minimum thickness of 14 inches
  • Moisture content shall not exceed 20 percent.
  • Bales shall be bound with ties of either polypropylene string or baling wire

Because straw is usually locally available it is viewed as a readily available material. Straw bale building is the most popular natural building technique in practice today. When designed for green living, a straw bale home is one of the most comfortable and efficient style of homes available today. Some folks even host old-fashioned bale-raising parties to get their walls up. Could there be one in your future?

straw6

Why Build a Straw Bale Home?

Renewable Resource
Straw is an abundant, renewable resource perfect for a sustainable construction and home design method, which can be engineered to meet your local building department requirements. Have you seen all those cereal boxes on the grocer’s shelf? The making of those cereals produces over 200 million tons of waste straw each year in the US alone! Most of it is burnt, sending up billowing clouds of smoke, polluting our air.

Building with the waste product of our farms is not only renewable but also keeps the air clean. Is also provides an excellent sustainable form of insulation to keep your home cool in the summer and warm in the winter. Not only that, but constructing a typical house requires more than an acre of trees and generates four pounds of construction waste per square foot. When you build a straw bale home, you save our forests.

Energy Efficient
Instead of using petroleum-based insulation products to fill walls, the entire wall is built from a natural, energy-efficient insulating product—straw. Because of its energy efficiency—a straw bale home can lower your energy bills by up to 75%—straw bale house construction is promoted by the federal government.

Quiet
The naturally thick sheltering walls offer a sense of protection and sanctuary from the outside world that conventional homes often do not. The thick bale walls eliminate almost all unwanted outside noise. Conventional homes do little to block noise.

Healthy
Natural building materials allow you to breathe easy in your home. Straw bale homes offer an alternative to “Sick House Syndrome.” New homes today are polluted with chemicals from building materials that create allergies, asthma, ill health, and fatigue. Using natural materials and sustainable structural design eliminates this problem.

Beautiful
Straw may seem like a simple material, but the construction of a straw bale home can result in a beautiful structure. It’s easy to create beautiful, curved, sculptural walls.

Increased Fire Resistance
Conventional construction offers only a 20-minute burn resistance. Because of the density of the bales and the thick plaster, straw bale home construction yields a 60-minute burn resistance.

Energy Efficient and Quiet

RENEWABLE BUILDING MATERIAL – instead of using petroleum based insulation products, the home is built from a renewable resource – straw. This method of building is now promoted by the federal government (http://www.energy.gov/) A home constructed out of straw bales can lower your energy bills by up to 75%!

Myths About Straw Bale Home Construction

Myth: Straw Bale Homes are Not Sturdy
Are you thinking of the big bad wolf? Do not worry! Your straw bale home or building will be engineered for wind, seismic, lateral, and vertical loads—as well as the big bad wolf. There are several ways that a straw bale building can resist lateral forces:
Straw bale wall assembly with reinforced plaster skin
Diagonal Bracing System
Engineered Frame
Hybrid System
A combination of the reinforced plaster skins and the engineered brace frames produces a strong structure that is easy to frame, bale, and plaster and will resist all seismic and wind forces.

Myth: Straw Bale Homes Will Rot or Grow Mold
As long as the house is designed and the materials drained correctly, there is no need to worry about mold or rot in the walls of a straw bale home. There are straw bale houses that have been standing for hundreds of years and are doing very well.

Myth: Straw Bale Homes Will Catch Fire Too Easily
Like a telephone book, condensed and packed straw will not catch fire due to lack of air/oxygen flow through the material. In addition, straw bale homes are covered with fire resistance stucco.

Myth: Straw Bale Homes Smell Like Barns
No way! Straw bales are a natural material and do not smell. Additionally, you will not experience the toxic gases released from manufactured items.

Myth: Straw Bale Home Construction is Cheaper
Straw bale home construction is about 15% more costly than traditional stick-frame construction. However, it is possible to complete some or all of the work yourself, making it cheaper. Additionally, the cost savings over time due to a straw bale home’s energy efficiency will make up for the extra cost.

Is There a Building Code for Straw Bale Home Construction?
Yes, it is included in a special section at the end of some codes such as Appendix S of the Oregon Residential Specialty Code. You can check with your local building department or use an experienced structural engineering firm such as Precision Structural Engineering to design and engineer your custom home plans.

Types of Straw Bale Construction
There are 2 types of straw bale homes—load bearing and non-load bearing. There are some important differences between the two.

Load Bearing:
Load-bearing straw bale homes (infill design) are constructed so the bales are stacked within a structural framework, such as steel, wood, etc. These buildings can be more than one-story. There must be a height to width ratio of 5.6 to 1 and openings shall not exceed 50% of the total wall area.
Non-Load Bearing:
In non-load bearing straw bale homes, the stacked bales support all or part of the roof. These homes are limited to one story.

straw3

The thick bale walls eliminate almost all unwanted outside noise. Conventional homes do little to block noise.

  • Beauty
  • Health
  • Building with the waste product of our farms keeps the air clean.
  • Natural building materials allow you to breathe easy in your home. Straw bale offers an alternative to “Sick House Syndrome.” New homes today are polluted with chemicals from building materials that create allergies, asthma, ill health and fatigue. Using natural materials eliminates this problem.
  • Beauty of natural colors and the bales have also been found to be pest resistant. Another advantage is the ease of creating beautiful, curved, sculptural walls. The naturally thick sheltering walls offer a sense of protection and sanctuary from the outside world that conventional homes often do not.

Fire resistance

  • Increased fire resistance
  • Conventional construction offers only a 20 minute burn resistance.
  • Because of the density of the bales and the thick plaster, bale walls yield a 60 minute burn resistance
straw8

The Truth Behind the Myths about Straw bale construction

The big bad wolf. Do not worry, your building will be engineered for wind, seismic, vertical loads and the big bad wolf. Straw will rot in the walls. Not if building is designed and drained correctly. Straw will catch on fire way too easily. Like a telephone book, condensed packed straw will not catch fire due to lack of air/oxygen. In addition, it will be covered with fire resistance stucco. It will grow mold. As long as the house is designed and drained correctly, no worry about mold. There is a house that has been standing for hundreds of years and doing very well. It will smell like a barn in my house. No way. Straw bales are a natural material and you will not get the gas released from manufactured items. It is cheaper to build with bales. Straw bale construction is about 15 % more than traditional stick framing construction. However, if you do the work yourself, it could be cheaper.

straw5

 

Is there a Building Code for Straw bale construction?

  • Yes, it is included in a special section at the end of Some Codes such as Appendix R of the Oregon Residential Specialty Code
  • Please check with your local building Department

Types of Straw Bale Construction

There are 2 types of straw bale homes- Load bearing Limitations: Height: One Story with height to width ratio of 5.6 to 1. Openings shall not exceed 50% of the total wall area Non-load bearing The difference between the two is that in the load-bearing style, the stacked bales support all or part of the roof. Non-load-bearing homes are limited to one-story. Load-bearing styles, aka, infill design, is constructed so the bales are stacked within a structural framework, such as steel, wood, etc. These buildings can be more than one-story.

How do Straw bale building resist Wind and Seismic forces?

There are several ways that a straw bale building resist lateral forces

  • Straw bale wall assembly with reinforced plaster skin
  • Diagonal Bracing System
  • Engineered Frame
  • Hybrid System

A combination of the reinforced plaster skins and the engineered brace frames produces a strong structure that is easy to frame, bale and plaster.

Resources and Links

As experienced residential structural engineers, PSE has completed many straw bale home projects. From the design of your custom home plans to construction management, PSE provides everything you need to build a straw bale home. For more information about straw bale home construction, please visit strawbale.com

What a Structural Engineer Provides for a Custom Home

What is “Building Green?”

Sustainable Home Building Materials

How to Begin Green Home Designs with Precision Structural Engineering

Additional Images