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Summer Heat Protection
To super insulate our house against summer heat, we have chosen to use natural wood-fibre insulation from Europe. This Wood-fibre insulation is made from timber waste products or wood from sustainably managed forests. It is produced in both rigid and flexible forms. The rigid form is used for sheathing and sarking on roofs, walls and floors, whilst the flexible form is used for interior insulation of walls and ceilings.
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It is vapor permeable and helps regulate humidity in the air.
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Because natural wood-fibre insulation is not made in Australia we have chosen to import the insulation from Steico, a German company that has excellent environmental credentials. The company is dedicated to producing a product that is both healthy and effective against heat and cold penetration. The end result is an easy-to-install, natural product that keeps the home well insulated and, therefore, thermally comfortable. This also has a follow on effect in that energy bills for heating and cooling are dramatically reduced.
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It's all about low Thermal Diffusivity
To protect our homes from absorbing the intense heat of summer an insulation with high density, low conductivity and a high specific heat capacity is required This type of insulation has a very slow temperature transfer time (or low Thermal Diffusivity). Steico boards and batts have this very special combination of elements. If you compare Steico's Flex (a semi-rigid batt) with mineral wool, the Flex has a Thermal Diffusivity rating of 13, whilst the mineral wool has one of 53. This means that the wood-fibre batts have 4 times the capacity to resist summer heat. If you also use a woodfibre sheathing board, the boards have almost 18 times the capacity to resist heat as mineral wool.
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Another way to compare insulation materials is by measuring it's amplitude dampening and phase shift. These measurements are vital for summer heat protection, just as the U value is vital for a winter thermal comfort measurement.
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Amplitude dampening is a measurement of the difference between the fluctuations in the external and internal temperatures. When the temperature fluctuates dramatically outside (for example, between 18 and 42 degrees = 24, and if the house can maintain a very low fluctuation in temperature (between 19 and 21 degrees = 3) then the building has been dampened from the external to internal side by 24/3 - a factor of 8.
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Phase shifting is the time span between the highest external temperature and the highest internal temperature. The aim of efficient summer heat protection is to delay the transfer of heat, until it cools down outside and the heat can be released back outside. A phase shift of 10 hours is to be desired. Wood fibre insulation achieves this by its density, low conductivity and thermal storage capacity.
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