Warming up to Energy Efficiency
Warm up to energy efficiency and help your customers with their facility planning by understanding how to calculate insulation value and compare insulation efficiencies of building materials.
A material's R-value measures its resistance to heat flow; a higher R-value signifies greater resistance. The 'true" thermal performance of building envelopes is most accurately determined through a two-step process that combines Isothermal (Series-Parallel Path Method) Analysis and Thermal Dynamic Building Envelop Analysis. Both of these calculation methods and the resulting summaries are based on information provided in the ASHRAE handbook of Fundamentals and ASHRAE/IESNA Energy Standard 90.1-1989 (adopted as the Model Energy Code). Isothermal Analysis accurately predicts the effects of irregular sized and spaced penetrations (thermal breaks) through an insulation layer, like windows or doors.
The second step in determining "true" thermal performance is Mass Analysis. This method incorporates the facility design, occupancy classifications, internal power generation assumptions, climate load factors as well as other construction inputs in order to determine the Btu consumption reduction for a facility built with mass and insulation versus a facility constructed with insulation alone. This yields a direct comparison between design R-value and actual performance R-value, which results in an "Equivalent R-value " rating for an insulated concrete wall panel.
In order to accurately compare energy efficiency due to mass effects, the C-value or conductance of a material is also used. A materials C-value is determined by the following equation, C = k/n, where k = conductivity and n = material thickness. Some products like concrete masonry units that do not have a homogenous thickness determine only a C-value. So how do C-values compare? .... 8 " of wood has a "C-value = 0.1 to 0.14; 8 " solid concrete wall: C = 1.25 to 2.5; 8 " concrete masonry wall: C = 1.7 - 2.2; 8 " of steel would be around 125. The higher the C-value the easier it is to quickly store heat or cold, but you also need a large volume of the material. This is where concrete is at its best, not too high and not too low. It is just right.
In order to accurately compare energy efficiency due to mass effects, the C-value or conductance of a material is also used. A materials C-value is determined by the following equation, C = k/n, where k = conductivity and n = material thickness. Some products like concrete masonry units that do not have a homogenous thickness determine only a C-value. So how do C-values compare? .... 8 of wood has a "C-value = 0.1 to 0.14; 8 " solid concrete wall: C = 1.25 to 2.5; 8 " concrete masonry wall: C = 1.7 - 2.2; 8 of steel would be around 125. The higher the C-value the easier it is to quickly store heat or cold, but you also need a large volume of the material. This is where concrete is at its best, not too high and not too low. It is just right.
Today, the inherent energy efficiency of concrete structures and diverse finish options give insulated precast concrete wall panels a dramatic advantage over other building materials for commercial construction. Call one of our MPA members today to find out how the inherent energy efficiency of a total precast concrete structure or by adding insulated precast wall panels to your next project can save your clients money year after year.
Summer 2005 Industry News
