Abstract
Natural, or ‘green’ insulation materials, have become more popular for the ‘ecologisation’ of construction activities. The ecological aspects for such materials are being widely analysed, but experimental data about their physical properties when installed in building constructions remains lacking. In this study, pressed samples of three locally wild grown agricultural materials – rye, reed, and hemp – are analysed. Thermal conductivity measurements were carried out using the hot plate device. Comparison with widely used mineral insulation materials shows that thermal conductivity for simple pressed materials are roughly three times higher, and are comparable to plywood and cross-laminated timber insulation properties. Additional experiments regarding such materials include measurements of hygroscopic sorption properties (adsorption/desorption), determined using the dynamic gravimetric method at different temperatures and a wide, relative humidity range. The results obtained show that the difference in all studied materials appeared only at high humidity values; the rye straw and reed spikelets adsorbed more water than other materials, which is important for potential indoor air humidity assessment.
Highlights
In recent years, the EU adopted several directives related to energy efficiency, e.g. the Energy Efficiency Directive 2012/27/EU [1], which requires a significant reduction in buildings’ energy consumption through, e.g. the introduction of nearly zero energy buildings
Insulation materials made from agricultural and plant products are mostly soft and compressible; it is very important to choose the optimal pressure on a specimen in the hot plate device, a too-high compression pressure will squeeze out the air, which will lead to incorrect results, due to increasing thermal conductivity
Thermal conductivity for similar unconventional natural raw materials like sunflower stalks, corn cobs or hemp shives is in range 0.9...1.1 W/(m·K) [4, 7], which is very close to the measured values
Summary
The EU adopted several directives related to energy efficiency, e.g. the Energy Efficiency Directive 2012/27/EU [1], which requires a significant reduction in buildings’ energy consumption through, e.g. the introduction of nearly zero energy buildings (nZEBs). To meet these requirements, the industry will need to improve the efficiency of existing materials, optimise their use as building structures, as well as develop novel, sustainable, and ecological construction materials [2]. Natural insulation materials can be made from vegetal or animal sources. Information about the thermal properties of other unconventional building insulation materials can be found in [4, 5]
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