straw bale construction

STRAW STRA W BALE BALE CONSTRUCTION

STRAW BALE CONSTRUCTION Straw-bale Straw-bale construction is a building method that uses bales of o f straw 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 •

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Auroville, Pondicherry

CURRENT BUILDING SITUATION AND ENVIRONMENTAL CONCERNS •

High energy intensity required in the manufacture of modern building materials

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Reduction in pollution and green house emission

Comparison of pollutant emissions between SBB and CBB

Straw bale

Cement brick Clay brick

wall Energy

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

required for manufacture r-value/ inch

1.5

.2

.5

Why build with straw? •

Eco- friendly

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Energy Efficiency

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Ease of Use

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Safety

Straw bale •

Size 100 x 45 x 40 cm

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usually wrapped with two, sometimes three, or more strands of knotted twine

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Weight 20-27 kg

Straw bales should be •

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Dry Dense Well tied Pure Fresh Consistent

Straw baler

Fire resistance •

Bales are typically too dense (lacking in oxygen) to support combustion

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Dry density varies between 110-128kg/m 3 High silica content (4-14%) impedes combustion

by charring

Insulative properties

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High thermal efficiency reduces the energy requirements for heating and cooling

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 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

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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.

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a moisture barrier or capillary break between the bales and their supporting platform.

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The straw bales in the walls are stacked in a manner similar to bricks or concrete blocks, in running bond.

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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

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bales are either wrapped outside the framework or in filled between the framing members

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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

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Lime plaster

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Earth plaster

Lath Galvanized lath should be provided if the wall is to hold stucco

Moisture concerns 

Presence of moisture leads to growth of molds

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Moisture barriers and application of wall covering prevent moisture penetration

LIMITATIONS •

High Space Requirements For The Straw

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Limited To Two Storeys

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Lack Of Codes

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Lack Of Qualified Professionals