Abstract
Common wheat is currently the most widely grown cereal and its grains are mainly used to produce white bread. Contrary to plant seeds, the plant itself may be considered an agricultural waste which is used as an animal feed, soil fertilizer, or pelletized solid fuel to produce heat energy. While wheat straw is used widely in sustainable building construction, mostly as straw bales, the use of the thin dry husk around the grain, the wheat chaff, remained unexplored. An insulation panel made of a medium-density fiberboard (MDF) envelope and wooden studs was manufactured. The 150-mm gap between the MDFs was filled with dry wheat chaff. The thermal transmittance of the panel was determined under static and dynamic thermal conditions using a modified guarded hot box method. The results were compared to an insulation panel of the same construction that was filled with mineral wool. The thermal transmittance of wheat chaff under steady-state and dynamic conditions was 0.307 W m−2 K−1 and 0.298 W m−2 K−1, respectively. While in steady-state conditions the mineral wool outperforms the wheat chaff insulation, after a period of dynamic thermal loading, the ability of both insulations to resist heat-energy dissipation becomes similar. In conclusion, wheat chaff agrowaste seems to be a promising environmentally friendly alternative to artificial thermal insulation. Moreover, the determination of the thermal transmittance of bio-based materials with relatively high specific heat capacities under dynamic thermal loading, provides more accurate results, compared to steady-state conditions.
Highlights
Over the last two decades, one can observe an increasing interest in green materials, technologies, and services
- After 88 h of dynamic thermal loading, mineral wool showed a 5% higher U-value compared to steady-state conditions, while wheat chaff showed a 3% lower U-value
The total heat flow depending on time, as the total energy leaked through the panel Esearched (Wh), was calculated using Usearched for every minute according to the following equation: Esearched = Usearched·A·(Tai − the cold chamber (Tae)) ·t where Usearched is the thermal transmittance (W m−2 K−1) given by the calculation using a solver function, A is the surface of the panel (m2), Tai − Tae is the difference in air temperatures between the hot and cold side of the sample (K), and t is the time (h)
Summary
Over the last two decades, one can observe an increasing interest in green materials, technologies, and services. Technical standardization, quality control, and mass production are difficult, perhaps leading to certain caution or a lack of confidence of the developers, builders, and, investors This is little discomfort compared to the long-term performance of bio-based materials and their environmental benefits, especially when considering the EU Directives 2010/31/EU [21] and 2012/27/EU [22] that aim for considerable energy-consumption reduction of the building industry in the very near future. For this reason, any research focused on testing real-size sustainable demonstrator samples is important as it can convince builders and investors to make greater use of such energy-saving renewable materials. The thermal performance in the range of +6 ◦C to −13 ◦C was found
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