Newton House

Answers to some of those
Frequently Asked Questions

Can I Build with sugar cane bales ?

Sugar cane mulch have been used in Queensland due to there availability, affordability and they are shapes like straw bales. I have a few concerns about them - though time will tell whether these are founded.

1. Termites have been reported to have been found in bales of sugar cane.
2. Sugar cane mulch will break down more readily then straw bales.
3. I don't believe that sugar cane mulch resists moisture in its thick stems and flat leaves compared to straw.
4. The flat leaves of sugar cane are more difficult for render to adhere to.

To observe how sugar can would perform on my property I conducted my own accelerated failure test. You can see the results of this here.

Having built with a few different quality straw bales, sugar cane and grasses; I can not emphases enough the benefit paying for building quality straw bales. This will substantially reduce the work and time during construction and rendering.

Who do I need to draw my plans?

A Draftsman completed their training at TAFE and can draw up basic plans. Use a draftsman for your house if you have a design you are happy with and just need it drawn up.

A Designer went to Uni for 4 years and has skills at drafting and providing design concepts. There are some restrictions eg can't design skyscrapers. A designer or architect will be able to help you with residential plans. I work with a good designer who has a sound knowledge of straw bale construction and passive solar design.

An Architect went to Uni for 6 years. Once an architect they specializing in a diverse choice of careers - sky scrapers, residential, commercial, industrial, units, bridges, sustainable design etc.

Like any professional groups - they all have areas they specialize in. Selecting someone with experience with straw bale construction is the most important thing you can do when selecting the person to draw your plans. Their understanding of straw bale will ensure you get the most of you design coupled with good Straw Bale practice. They will be able to save you money during construction by designing a system that is suited to strawbale construction.

The person who draws your plans will work along with a structural engineer. This is the person who makes sure the footing are appropriate for the soil types, the tie downs are appropriate for the wind loads and that the beams, brackets, nuts and bolts are all the right size. It can't go to council without a structural engineers drawings along side the architects drawings. Again an engineer experienced in straw bale construction will be able to design a simple wall system that will meet council requirements for your land.

Earth-n-Straw commitment is not to straw bales, but to environmental sustainable design and living. Any referrals from earth-n-straw will be to businesses that reflect this Commitment. For local contacts click here

Can you build from straw bales in hot humid climates?

I have done a literature review on available research on this topic. You can review this data information here.

What is sustainable building?

Straw bale garden walls have been built before, but in the face of breaking the 2 cardinal rules of straw bale construction. If you have a garden wall should have a roof over it to prevent water penetrating into the core of the wall. Straw bale walls are constructed with a rendered wall that can breath - if not the wall develop condensation on the inside and rot may occur in the straw. Straw bale garden walls have been built by using additives to your render that will let water vapour but not rain pass through the wall.

How much will an average 3 bedroom house cost?

We not builders - so do not take part in costing.
You will find that a builder will not take part in costing either until you have purchased your land and have a set of plans.

The best I can give you is some guidelines.
The wall cost is approx 20% of the total cost of construction of a building.
A Straw Bale wall is 300mm wider then a brick veneer wall system.
Final costing will vary depending on the detailing and type of render that you use on the wall.

Will I still need air conditioning?

If you are considering straw bale as medium for passive solar design - you can not go wrong using straw bales for insulation. Use it as your outer envelope of your home. R-value of straw bales is 4.8. This provides a great esky like qualities in summer and thermos like properties in winter.

No building material works in isolation when considering passive solar design.

The render over straw bale walls provides a little thermal mass, but I recommend that you couple the insulated external walls with a thermal mass on the inside of your home. Mud brick wall, rammed earth wall, earth floor, slab on ground all provide excellent mediums for heat storage.

http://www.ecobuildnetwork.org/
http://www.buildinggreen.com/features/straw/straw.cfm
http://sol.crest.org/efficiency/straw_insulation/straw_insul.html
http://members.axion.net/~enrique/roundstrawhouse.html

I read somewhere that....

You can build with straw bales in the slab (such as a waffle pad) or in sub-surface walls. Bales in the slab have historically had a very high failure rate - don't go there. The combination of moisture and heat in the soil will lead to a rapid failure in our climate.

Re bales in the ceiling - this has been done, I saw quite a few while I was in Europe as a form of insulation. You will need to render the bales to provide protection from fire and vermin. This will add weight and cost of the ceiling. Your engineer will need to ensure that your roof structure is appropriately designed.

I have some dry straw, though it is more grey then yellow.

Don't use the grey / black bales! Sounds like they have had some exposure to moisture in the past - the black are mould that started to grow. Even though you bales may now be dry the spores are there ready to bloom with any future exposure to moisture or humidity. I early stages of rot from mould it may be some dark discoloration - in advance stages it is a pile of black goo where the bale was.

Can I use straw bales for my sound studio?

I got this information the acoustic properties of Straw Bales at: http://www.users.bigpond.com/brookman/strawbaleBuildingProject.htm#Sound%20insulation

Can I Build a straw bale garden wall in Queensland?

What about the big bad wolf and cyclones?

Once constructed, bale walls are very strong and stable. When tested, bale walls have withstood the equivalent of a significant wind of over 215 km/hr.
*ASTM E72 80 transverse load testing of load-bearing straw bale walls, Building Research Centre of the University of New South Wales, Australia, 1998

What will happen in the case of a fire?

Won’t straw bale walls be easy to burn? Tightly compacted straw bale can not suppor rapid comustion, it will be similar to trying to burn a telephone book. Now wrap the book in 5cm of plaster. There is too little oxygen to support combustion. During research plastered straw bale walls have withstood temperatures of up to 1942°F for two hours; the temperature rise on the unheated side averaged less than 10°F.*
*ASTM E-119 Fire Test, SHB Agra, New Mexico , USA, 1993

What about rodents and insects?
The straw bale walls will be covered with about 1.5 inches of hard, earthen plaster on both the inside and outside, creating a very strong deterrent to critters. And unlike hay, the straw itself has no nutritional value -- it is the stalk that remains after the seed heads, such as wheat or hemp, are removed.

Are straw bale walls strong enough to hold up a roof? What about a second story?
Yes, you can build one or two storey load-bearing straw bale buildings. There has been a lot of testing on the compressive, lateral and sheer strength of bale walls. Recent compression testing of an earth plastered straw bale wall at Queen's University in Kingston, Ontario, revealed that the wall surpassed conventional stick-frame walls in this regard.

Can straw bale techniques really make a difference to the environment?
“The embodied energy for the conventional frame house was 509,000 KBtus. The embodied energy for the low impact straw bale house is 41,000 KBtus, or about one twelfth that of the frame house.”*
*Investigation of Environmental Impacts, Straw Bale Construction, by Ann V. Edminster, University of California , Berkeley , 1995.

What do you mean by "embodied energy"?
Embodied energy is the non-renewable energy consumed in the acquisition of raw materials, their processing, manufacture, transportation to site and the construction process. It also includes the energy consumed to maintain, repair, restore, refurbish or replace materials, components or systems during the lifetime of a building.

Fire Testing in Germany

Answers to some of those Frequently Asked Questions