For problems where the temperature variation is only 1dimensional (say, along the xcoordinate direction), Fourier's Law of heat conduction simplies to the scalar equations, 
where the heat flux q depends on a given temperature profile T and thermal conductivity k. The minus sign ensures that heat flows down the temperature gradient.
In the above equation on the right, represents the heat flow through a defined crosssectional area A, measured in watts,
Integrating the 1D heat flow equation through a material's thickness Dx gives, 
where T_{1} and T_{2} are the temperatures at the two boundaries. 
In general terms, heat transfer is quantified by Newton's Law of Cooling,
where h is the heat transfer coefficient. For conduction, h is a function of the thermal conductivity and the material thickness,
In words, h represents the heat flow per unit area per unit temperature difference. The larger h is, the larger the heat transfer Q. The inverse of h is commonly defined as the Rvalue,
The Rvalue is used to describe the effectiveness of insulations, since as the inverse of h, it represents the resistance to heat flow. The larger the R, the less the heat flow . R is often expressed in imperial units when listed in tables. Conversion to SIunits is provided in the Units Section. To convert R into a thermal conductivity k, we must divide the thickness of the insulation by the R value (or just solve for k from the above equation),
