U-value of simple layered structure. Define your structure by entering the material and thickness for each layer, inside to out. Includes condensation risk assessment.
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The U-value assesses the rate of heat loss / gain through all the thicknesses of the combined elements that make up a building component such as a wall, floor or roof. It is measured in units of W/m2. K (Watts per metre squared Kelvin). It is a way of measuring the insulating properties of the building element.
U-value, or thermal transmittance (reciprocal of R-value)
Thermal transmittance, also known as U-value, is the rate of transfer of heat through a structure (which can be a single material or a composite), divided by the difference in temperature across that structure. The units of measurement are W/m²K. The better-insulated a structure is, the lower the U-value will be. Workmanship and installation standards can strongly affect the thermal transmittance. If insulation is fitted poorly, with gaps and cold bridges, then the thermal transmittance can be considerably higher than desired. Thermal transmittance takes heat loss due to conduction, convection and radiation into account.
Calculating U-value
The basic U-value calculation is relatively simple. In essence, the U-value can be calculated by finding the reciprocal of the sum of the thermal resistances of each material making up the building element in question. Note that, as well as the material resistances, the internal and external faces also have resistances, which must be added. These are fixed values.
Vesma have created a simple tool to support calculating u-values of simple layered structures for your project.
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