straw bale construction

STRAW BALE CONSTRUCTION

STRAW BALE CONSTRUCTION

Straw-bale construction is a building method that uses bales of straw (commonly wheat, rice, rye and oats straw) as structural elements, building

insulation, or both.

HISTORY

• First house in Nebraska(US), 1936. • Andaman Earthship in Andaman island

• Auroville, Pondicherry

CURRENT BUILDING SITUATION AND

ENVIRONMENTAL CONCERNS

• High energy intensity required in the

manufacture of modern building materials

• Reduction in pollution and green house

emission

Comparison of pollutant emissions between SBB and CBB

Straw bale wall

Cement brick Clay brick

Energy required for manufacture

.115Gj/tonne 6-8GJ/tonne 2-7 GJ/tonne

r-value/ inch 1.5 .2 .5

Why build with straw?

• Eco- friendly

• Energy Efficiency

• Ease of Use

• Safety

Straw bale

• Size 100 x 45 x 40 cm• usually wrapped with two, sometimes three, or

more strands of knotted twine• Weight 20-27 kg

Straw bales should be

• Dry

• Dense

• Well tied

• Pure

• Fresh

• Consistent

Straw baler

Fire resistance

• Bales are typically too dense (lacking in oxygen)

to support combustion

• Dry density varies between 110-128kg/m3

• High silica content (4-14%) impedes combustion

by charring

Insulative properties

• High thermal efficiency reduces the energy

requirements for heating and cooling

• R- value between 30-50

• Sound insulation

Method

• Straw bale buildings use the same foundation, flooring and

roofing technologies similar to any conventional type of building

• Basements, slabs and pier foundations can all be easily

adapted to straw bale construction. Similarly, prefabricated

trusses can be used to provide the roof structure.

• a moisture barrier or capillary break between the bales and their

supporting platform.

• The straw bales in the walls are stacked in a manner similar to

bricks or concrete blocks, in running bond.

• Window and door openings are created using wide, rough frame

wooden bucks inserted into the walls during construction.

straw bale wall

1.Post and beam type

• Use timber, concrete or steel frames to support roof load

• bales are either wrapped outside the framework or in filled

between the framing members

• Straw bales are mainly used as insulation

2. Load bearing wall

• Bale walls themselves support

the roof load

• Bales are precompressed

before placing to avoid settlement

• A structural roof plate

is placed on top of the walls.

Wall coverings

Types of stucco

• Cement stucco

• Lime plaster

• Earth plaster

LathGalvanized lath should be provided if the wall is to hold stucco

Moisture concerns

Presence of moisture leads to growth of molds

Moisture barriers and application of wall covering prevent moisture penetration

LIMITATIONS

• High Space Requirements For The Straw

• Limited To Two Storeys

• Lack Of Codes

• Lack Of Qualified Professionals

THANK YOU