The technical name for which we use the shorthand uvalue is thermal transmittance. A low u value usually indicates high levels of insulation. A uvalue is typically a low number because it is a rating of how much heat energy is lost or gained. Construction materials ppi united states 2018 statista. If we look at the two values mathematically, uvalue is the reciprocal of rvalue. In simple terms, rvalues measure the effectiveness of insulation and a higher number represents more effective insulation. In construction, the rvalue is the measurement of a materials capacity to resist heat flow from one side to the other. Uvalue is the term used to describe the heat transfer coefficient of a building element e.
The lower a uvalue, the better the insulation quality of the building element. R value table common building materials resistivity r per inch thickness resistancer for given matl. The production price index ppi for construction materials and components in the united states has risen fairly steadily, reaching 235. Uvalue is generally used to rate door or window units. Uvalues for common materials reference table for u values u value is the coefficient of transmission, i. The uvalue of a building component like a wall, roof or window, measures the amount of energy heat lost through a square metre m 2 of that material for every degree k difference in temperature between the inside and the outside. Uvalues are measured in watts per square metre per kelvin wm. U values are important because they form the basis of any energy or carbon reduction standard. The uvalue describes the insulation quality of a building. Rvalues of insulation and other building materials. Explore alternatives to the prescriptive wall insulation more ci and less cavity r value, etc. Determine u factor input to energy model or energy rating programs must use codecompliant insulation materials must substantiate u factor for assembly. For example, a double glazed window with a uvalue of 2.
Prescriptive rvalues, ufactor equivalents, and total ua. For example, a material with an rvalue of 5 has a uvalue of 0. A range of uvalues are indicated below for the purposes of comparison only. Tables of uvalues table a1 indicative uvalues wm2k for windows and rooflights with wood or pvcu frames, and doors gap between panes adjustment 6mm 12mm 16mm for rooflights or more in dwellings3. The lower the uvalue, the more energy efficient the system in question will be. Uvalues by measurement or calculation according to the standards given in section 0 should be used in preference to the data given in these tables. They are useful as it is a way of predicting the composite behaviour of an entire building element rather than relying on the properties of individual materials.