Economic Insulation Thickness
Economic insulation thickness is the thickness at which total cost - the capital cost of the insulation plus the value of the heat it still lets escape over its life - is lowest. Adding more insulation always cuts heat loss but with diminishing returns, so there is a cost-optimal thickness for each line size, temperature and energy price.
As insulation thickness increases, annual heat loss falls but installed cost rises. Plotting the sum of the two against thickness gives a U-shaped total-cost curve whose minimum is the economic thickness. Higher energy prices, higher operating temperatures and longer run hours all push the optimum thicker; standards such as ASTM C680 and tools like 3E Plus are used to compute it.
The same logic explains why insulating previously-bare fittings is almost always justified: going from zero to even a modest jacket thickness sits far to the left of the cost minimum, where each unit of insulation removes a large amount of expensive heat loss, giving short paybacks.
Related reading
Related terms
Heat Loss · Thermal Insulation · Thermal Conductivity (λ) · U-value (Thermal Transmittance) · Energy Audit · Boiler Efficiency · Sensible Heat · Total Cost of Ownership (TCO)