Building a Straw Bale Home
We all want to live in a home that is comfortable and energy efficient. We want our home to be healthy, and for the air that we breath in it to free of harmful chemicals. And we want our home to be unique, beautiful, and gentle on the earth. Straw bale homes provide all these qualities, and more.
A well-designed home invites lots of natural light into living spaces, is warm and quiet, and provides a deep sense of well-being from knowing that the materials are natural and free of harmful toxins or chemicals so common in many conventional building materials today. The home should be free of drafts, regulate humidity, and store warmth/coolth so that temperatures are stabilized. Many different building components will have to be brought together to achieve these good design qualities, but when it comes to walls, the straw bale/plaster combination creates a fantastic compliment to this package.
This combination creates a living, ‘breathing’ wall, that is exceptionally insulating, fire resistant, and quiet. The great thickness of the walls provides unlimited aesthetic possibilities, such as deep window seats, built-in furniture and niches.
How We Can Help
Please visit our ‘Building Services – ‘How We Can Help’ page for information on how we can support your straw bale project.
Here are 10 reasons that straw bale walls stand out:
- Great insulation: straw bale walls achieve an R-value of R-27.5 or greater. A typical 2Ã—6 stud wall with maximum fiberglass insulation is rated at R-19.
- Better air quality: straw is a natural, non-toxic building material, that when covered with a natural clay finish is not only zero VOC but contributes to healthier indoor air quality by regulating humidity levels and releasing negative ions.
- Gentle on the earth: straw is an agricultural waste product leftover from the production of cereal crops – wheat, rice, rye, flax, etc. Straw bale building is an excellent example of up-cycling.
- Very good fire resistance: straw bale walls have a very good fire rating. An earth plaster wall can withstand temperatures in excess of 1400oF for 1 hour, while cement-lime walls can withstand these temperatures for 2 hours without fail. A typical stick-built wall with drywall has a 30 minute fire rating.
- Making friends with moisture: unlike conventional building that goes to war with moisture by wrapping homes with plastic inside and out, the straw bale/plaster combination seeks to make friends with moisture by providing a vapour permeable wall system that allows moisture to safely pass through the wall before it can create problems.
- Reduced material use: a plastered straw bale wall replaces the insulation, drywall and paint combination used in a conventional construction.
- Better sound quality: straw bales provide wonderful sound insulation and have a positive effect on interior acoustics.
- User-friendly: building with bales can create opportunities to involve friends, family, and community members through workshops, wall raisings, and work-bees.
- Beautiful: straw bale walls are aesthetically versatile. They can be made straight or flat, or be shaped to gently undulate, revealing the organic nature of the bales. Bales accommodate window seats, built-in furniture, and niches. They can be built to any style: from square and contemporary to handmade and hovel-like.
- Revolutionary: straw bale building is open source and collaborative, thereby shifting the dominant paradigm of home building which has become unnecessarily complicated, expensive, and proprietary. Building with bales is freeing and accessible, making them a perfect building material for those who seek to play a more active role in creating their shelter.
Why use straw to build homes?
There are many reasons to do this.
First, straw is a very good insulator and utilizing it will make a very efficient, high-performance home.
Second, straw is a plant-based material (a waste product of grain farming) that is widely available, making it a great choice for those wishing to lessen the ecological impact of their home.
Third, straw bale homes are a pleasure to live in. The combination of straw bale and clay or lime plaster (the material that covers the bale), is not only healthy for the environment, but it makes for a very healthy and pleasurable interior environment for those living in a straw bale home. The interiors are free of harmful chemicals, they manage humidity very well, and they offer a softness not found in most other building materials.
Lastly, straw bale construction lends itself to having the owners participate in the building of their home. Workshops, like those offered by Dirt Craft Natural Building, give people the tools and skills necessary to take an active role in the building of their own home.
But won’t straw rot in the walls?
Any cellulose-based building material (including wood) will decay if moisture is not properly considered. Careful attention is taken to ensure straw bales do not get wet in either the construction phase or while the home is being lived in. Proper foundation and roof design are fundamental in accomplishing this, as are the choice of plasters used to seal the bales from the elements. Detailing around doors, windows, and other penetrations are carefully considered to ensure health and longevity of the home.
Isn’t a straw bale home more likely to burn in the event of a fire?
The simple answer is no. Loose straw is very susceptible to catching on fire, though a tightly bound bale will smoulder, not ignite. Besides, straw bales are not left exposed to the elements but, rather, covered in 1.5 inches of plaster on both the interior and exterior, starving the bale of oxygen. Where there is not oxygen there can not be fire. Fire tests show that once a straw bale is encased in plaster, it is able to withstand an 1400 degree (F) open flame for more than an hour without any significant structural damage, a benchmark that demonstrates just how fire resistant straw bale homes are. For more information on fire testing, please visit our Straw Bale Resource Page.
What about mice and other pests?
Since straw is the stem of a plant, it doesn't contain any food value. And once the plasters are applied to the bales, inside and out, access to the straw is no longer available. The existence of sound, long lasting straw bale homes (>110 years) proves this to be true.
How much insulation does a straw bale house provide?
This will depend on a number of factors, the size of bales (2 or 3 string), whether they wrap the building or are placed between wooden posts, their orientation (on edge or on flat), etc. - but generally speaking, straw has an R-value of 1.45/inch. This means a two string bale laid flat will have an R-value of 27.5. Compare this to R-19, which is the standard for walls in new construction in Canada. R-values simply indicate the thermal conductivity, and thus describe the rate of heat transfer through a material or assembly. The higher the R-value the higher the performing it is.
What’s the difference between straw and hay?
Straw is the dry stalk of a cereal plant (like wheat, flax, oats, rye, rice, or barely) after the nutrient grain or seed has been removed. It's the material that is left over once the combine harvester has removed the more valuable tops of the plant. Hay is grass or legumes that have been cut, dried, stored to be used for animal feed. It is generally fed when there is a shortage of pasture or rangeland on which to graze animals, and especially during winter months.
Can you get insurance and/or a mortgage on a straw bale home?
Absolutely! This is not to say it will be the easiest thing to do in the world but many straw bale home builders have taken out mortgages and have gotten their homes fully insured. Your success in dealing with banks and insurers will largely depend on the person whom you are dealing and your ability to assemble the proper documentation, engineer-approved plans, a building permit, and a realistic, well-documented budget - to support your project.
How much does it cost to build a straw bale home?
As you can imagine, this will depend on many, many variables - the design, the size, other materials used in the construction, the cost of bales, how much time and work you're willing to contribute, etc. Generally speaking though, the straw is cheaper than most other systems that will yield similar performance but the labour to get a straw bale home complete may be more. This is because much of the cost of more conventional materials is accrued off-site, while straw bale construction tends to rely on more unprocessed materials, working them into their form on-site. Straw bale projects lend themselves nicely to those wishing to contribute time and labour to the building of their own home. Also consider that a straw bale home is unlike any other conventional home. It truly is a handmade home, giving those involved in its construction the ability to impress their care, love, and craftsmanship into the walls. The efficiency of a straw bale home will lessen the operational costs of the home - heating, air conditioning, etc. - compared to many other 'cheaper' building techniques. And finally, it's important to weigh the ecological costs of the materials we choose to build with, including those relating to the extraction, manufacture, transportation, use, and disposal. When all things are considered, a straw bale home provides excellent value.
Want More Information?
Be sure to visit our Straw Bale Resource Page for information on building codes, fire ratings, avoiding moisture issues, plaster systems, etc.