Search

This paper describes the hot-box testing (based on ASTM C1363-11) of seven straw bale wall panels to obtain their thermal conductivity values. All panels were constructed with stacked bales and cement-lime plaster skins on each side of the bales. Four panels were made with traditional, 2-string field bales of densities ranging from 89.5 kg/m3–131 kg/m3 and with the bales on-edge (fibres perpendicular to the heat flow). Three panels were made with manufactured high-density bales (291 kg/m3–372 kg/m3). The fibres of the manufactured bales were randomly oriented. The key conclusion of this paper is that within the experimental error, there is no difference in the thermal conductivity value for panels using normal density bales and manufactured high density bales up to a density of 333 kg/m3. However, because of lack of precision of the hot-box, no conclusions can be made on the true thermal conductivity of the high density bale panels. In addition, the panels tested were found to have significant voids between bales, and this is believed to have contributed to higher measured thermal conductivity values compared to those reported in the literature for normal density bale panels. Thermal properties may be affected for bales with higher densities than 333 kg/m3, therefore further testing is suggested.

Experimental data describing the mechanical performance of Portland cement- hydrated lime mortars used for straw bale construction is presented. Straw bale construction uses stacked straw bales plastered on each side to form load-bearing elements. Mortars used have slumps of approximately 50 mm, compared to slumps up to 279 mm for conventional masonry mortars. Cylinder and cube tests of a range of typical straw bale mortar mixes were carried out. The mortars had compressive strengths ranging between 0.3 MPa and 13 MPa. Empirical equations describing the relationships between compressive strength and curing time, w/cm ratio, proportions of lime, cement and sand, and modulus of elasticity are presented. The data show that cement-lime mortars for straw bale construction will have a higher modulus of elasticity and lower failure strain than a conventional mortar of equivalent compressive strength. The Modulus of Elasticity is on average 818 times the compressive strength of a straw bale mortar, compared to 100 to 200 times as reported in the literature for conventional mortar. The average failure strain for straw bale mortar is 0.00253 compared to 0.0087 to 0.0270 reported in the literature for conventional mortar.

The search for more sustainable construction methods has renewed interest in straw-bale construction. Rectangular straw bales stacked in a running bond and plastered on the interior and exterior faces have been shown to have adequate strength to resist typical loads found in one- and two-storey structures. The straw bales provide excellent insulation, while possessing low embodied energy compared to conventional insulation materials. The structural behaviour of a load-bearing plastered straw-bale wall subject to uniform compressive loading has been the focus of a number of studies reported in the literature. However, in a typical building wall, there will be numerous locations (such as around window and door openings) where the load paths produce areas of concentrated stress. The behaviour in these regions cannot necessarily be predicted using tests from uniformly loaded wall assemblies. This paper describes experiments on plastered single bale assemblies subjected to three-point bending. These a...

To date, much of the research on green roof technology has focused on the capacity for these systems to contribute to the cooling of buildings during summer months. The thermal performance of green roofs in cold climate conditions is critical to understanding the potential of these roofs to decrease energy use in buildings during winter. This paper compares the behavior of two green roof systems with that of a conventional built-up roof by making use of a novel hot box testing apparatus. The green roofs tested are classified as extensive systems. Each system included: a 3 mm thick styrene butadiene rubber waterproofing membrane, 0.2 mm thick polyethylene slip sheet, a 76 mm thick extruded polystyrene insulation layer, 2 mm thick filter fabric, a 51 mm drainage layer followed by a 2 mm thick filter cloth, either 100 mm or 150 mm growing medium, and a 25 mm thick wild flower vegetated mat. The conventional roof consisted of a 2 mm thick layer of Kraft™ vapour retarder bonded with insulation adhesiv...

The concepts of “green building” and “sustainable construction” have received tremendous interest in North America in the past decade, as shown by the growth in the numbers of L.E.E.D.™ ce...

The Haliburton 4C's Food Bank and Thrift Store building, shown in Figure 1, was designed and built in June through August 2005. The structure combines an impressive variety of sustainable ...

The structural performance of plastered straw bales under compressive loading is extremely important when considering the suitability of plastered straw bales as a construction material. Most currently available results do not investigate how different construction methods and practices can affect the strength of a plastered bale. The experiments discussed in this paper illustrate how the strength of the plaster, the thickness of the plaster and the orientation of the bale itself can affect the strength of the plastered bale. It was found that the bales plastered flat were 36% stronger than those plastered on edge. In addition it was found that although the plaster strength does affect the strength of the plastered bale, it does not have as significant an impact as the plaster thickness. It was also found that nearly all plastered bales tested had higher strengths than would be required in typical residential construction. The strengths were found to be in the same range as the values reported in the existing literature. The plastered bale modulus was found to be highly variable and un-predictable.