Straw Bale Construction Units, 450mm thick (450mm)
Highly insulating natural building material with R-value 4.8-9, excellent fire resistance (FRL 90-90-90 when rendered), suitable for all Australian climate zones and BAL ratings. Requires Performance Solution for NCC compliance.
Highly insulating natural building material with R-value 4.8-9, excellent fire resistance (FRL 90-90-90 when rendered), suitable for all Australian climate zones and BAL ratings. Requires Performance Solution for NCC compliance.
Straw bale construction units are compressed rectangular bales of cereal straw (wheat, rice, barley) used as structural insulation in walls. Standard Australian bales measure 900mm×450mm×350-400mm, weighing 16-20kg. When rendered with earth, lime or cement-based plasters, they provide exceptional thermal performance, fire resistance up to BAL-FZ, and acoustic insulation. Carbon-negative material when considering sequestration.
- Exceptional thermal insulation (R-value 4.8-9)
- Fire resistant when rendered (FRL 90-90-90)
- Carbon negative with sequestration
- Low embodied energy (<50MJ/m²)
- Excellent acoustic insulation
- Breathable wall system
- Agricultural waste utilisation
- Suitable for owner-builder construction
- Non-toxic, no VOC emissions
- Locally available across grain-growing regions
- 01 Exceptional thermal insulation (R-value 4.8-9)
- 02 Fire resistant when rendered (FRL 90-90-90)
- 03 Carbon negative with sequestration
- 04 Low embodied energy (<50MJ/m²)
- 05 Excellent acoustic insulation
- 01 Requires Performance Solution for NCC compliance
- 02 Moisture sensitive - needs careful detailing
- 03 Labour-intensive construction
- 04 Thick walls reduce internal floor area
- 05 Limited experienced contractors
- Density
- 90-110 kg/m³ (typical construction grade) kg/m³
- Specific gravity
- 0.09-0.11
- Porosity
- 85-90% %
- Water absorption
- <15% moisture content required for construction %
- Hardness
- N/A - compressible material
- UV resistance
- Poor - requires protective render
- Chemical resistance
- Moderate - alkaline compatible
- pH tolerance
- pH 6-9 optimal
- Surface roughness
- N/A - covered by render µm
- Tensile strength
- 0.01-0.02 MPa (perpendicular to straw) MPa
- Compressive strength
- 0.05-0.9 MPa (unrendered), 1.7-6.0 MPa (rendered) MPa
- Flexural strength
- Dependent on render - typically 0.5-2.0 MPa MPa
- Shear strength
- 0.02-0.05 MPa MPa
- Poisson's ratio
- 0.1-0.2 (varies with orientation)
- Impact resistance
- High - flexible response
- Creep resistance
- 20-80mm settlement typical under compression
- Embodied carbon
- -0.35 to -0.91 kg CO₂e/kg
- Carbon footprint
- -1.35 kg CO₂/kg (sequestered)
- Embodied energy
- 0.91 MJ/kg (baling and transport) MJ/kg
- Water footprint
- Variable - dependent on crop irrigation L/kg
- Recycled content
- 0% (agricultural by-product) %
- Renewable content
- 100% %
- Circular score
- Excellent - full biodegradability
- Combustibility class
- Non-combustible when rendered to AS 1530.1
- Fire resistance level
- FRL 90/90/90 (rendered)
- Ignition temp
- >300°C °C
- Flame spread index
- 0 (rendered surface)
- Smoke dev. index
- 0-3 (rendered)
- Heat release rate
- Minimal - oxygen-starved environment
- Material cost (range)
- $3-8 per bale
- Material cost (per unit)
- $35-50/m² (wall area, bales only)
- Lead time
- 2-8 weeks depending on season
- Lifecycle cost
- Lower than conventional due to energy savings
- Annual maintenance
- $50-200/year (render maintenance)
- Market availability
- Seasonal - harvest dependent
- Expected lifespan
- 50-100+ years with maintenance
- Maintenance interval
- Annual inspection, 5-10 year render touch-ups
- Warranty period
- Builder-dependent, typically 6-7 years