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Se hela listan på nachi.org Re: U factor-F factor-C factor-R factor Relations U factor IECC 2009 (thermal transmittance). The coefficient of heat transmission (air to air) through a building component or assembly, equal to the time rate of heat flow per unit area and unit temperature difference between the warm side and cold side air films (Btu/h*ft2*Degree F)[W/(m2*K)]. Both of these terms, R-value and U-value, are commonplace terms in the remodeling and construction industry and are used to define how energy efficient a material is. R-value is used to define the energy efficiency of a particular building material and originally was developed for measuring the thermal performance of insulation. R values rate one single material while U values measure entire components. For example R values measure how much heat loss passes through fiberglass insulation while U values rate how much heat can pass through a window component (glass, air, vinyl sash).

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The R-value is calculated using the U-factor’s reciprocal Described in their most basic terms, R-value is a measure of heat resistance, while U-factor (also know as U-value) is a measure of heat transfer (heat gain or loss). The lesser known K-factor is simply the reciprocal of the R-value of the insulation divided by the thickness. When you use these assumptions to compute the overall U-factor for the prescriptive R-value wall assemblies, they match right up with the U-factor requirements! As an example, let’s look at the IECC 2015 Residential Code requirements, found in Table R402.1.2 and Table R402.1.4.

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Vehicles. Fenestration and dehiscence What is Fenestration and How Can it Affect Value NAFS in the Measuring Performance: U-Factor - Efficient Windows.

U factor vs r value

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U factor vs r value

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where R is the distance from any point on the source to the observation point. Solution y x θ φ. R z r l/2 c) Explain why your chosen approximative formula gives the best value.
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KmW-1 r = The two fundamental borehole heat exchanger designs – the U-pipe and. av R Nordman · 2010 — Performance Factor (SPF), and what deviations may depend on. The SPF-value can be calculated for different levels of the heating system.

2005-04-01 · Generally used to compare the performance of windows, U-factor first was invented by engineers and scientists as a measure of the rate at which heat flows through 1 sq. ft. of material. The direct opposite of an R-value, a lower U-factor rating means that less heat will be lost.
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This is different than R-value that would be used to determine the energy efficiency of just the window pane, thus a window with a U-value of 1 is more energy efficient than an window with a U-value of 5. mathematical reciprocal of R-value; that is, U = 1/R and R = 1/U. For instance, a material with an R-Value of 5 has a U-value of 0.2 (1 divided by 5). As the R-value goes up, the U-value goes down, and vice-versa.