Effective R-Value  
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The Total Effective
R-Value performance of ICFs consists of three factors:
(1) the R-Value of the expanded polystyrene,
(2) the thermal mass of the concrete, and
(3) the enormous reduction in air leakage (infiltration).
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Insulating Value
First, the R-Value of BuildBlock's polystyrene alone is R-20, compared to wood frame's R-9 to R-15. So ICF
walls are expected to cut the conduction losses through foundation and above-grade walls by about half.
Air Infiltration
Air leakage accounts for as much as 40% of the heat load requirements of a wood
framed structure. Nothing blows through solid concrete! ICF walls reduce air infiltration by about half, compared to wood
frame.
Thermal Mass
But ICF walls
do more than cut down on the biggest types of energy loss. The concrete gives them the heat-absorbing property "thermal mass."
This is the ability to smooth out large swings in temperature. It keeps the walls of the house a little warmer when the outdoor
temperature hits its coldest extreme, and keeps the house a little cooler when the outdoor temperature is
hottest.*
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*Energy loss graphs and thermal mass information from
Portland Cement Association, Technology Brief 1
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As a result, with the combined performance of these three factors, ICF walls actually perform as
high as R-50 in some areas of the country.
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BuildBlock ICFs...Performs as high as R-50 Value. 
