Microporous Insulation Board vs. Calcium Silicate: A Thermal Conductivity Comparison

Calcium silicate board is the incumbent backup insulation in many ladles, kilns, and furnaces — and it is the material we are most often asked to compare against. This article puts our nano microporous insulation board side by side with calcium silicate on the numbers that matter to a specifier: thermal conductivity across the service range, and what the difference means for lining thickness and weight. All microporous figures below are measured values from our standard board; the comparison values for calcium silicate, ceramic fiber, rock wool, and insulating brick are the same reference data we publish on the standard nano insulation board page.

Thermal Conductivity Comparison (W/m·K)

Average temperature	Insulating brick	Rock wool	Ceramic fiber	Calcium silicate	Still air	Microporous
-100 °C	0.1180	0.0320	0.0300	0.0380	0.0160	0.0200
0 °C	0.1200	0.0330	0.0320	0.0400	0.0180	0.0210
100 °C	0.1220	0.0370	0.0360	0.0460	0.0200	0.0220
200 °C	0.1250	0.0550	0.0440	0.0550	0.0220	0.0210
300 °C	0.1300	0.0800	0.0600	0.0650	0.0250	0.0240
400 °C	0.1350	0.1200	0.0800	0.0800	0.0360	0.0240
500 °C	0.1440	0.1800	0.1100	0.0960	0.0440	0.0280

What the Numbers Mean in a Lining

Across the full range, microporous board runs at roughly one-half to one-third of the conductivity of calcium silicate — at 500 °C, 0.0280 against 0.0960 W/m·K. Two practical consequences follow. First, for the same cold-face temperature, a microporous backup layer can be one-half to one-third the thickness of a calcium silicate layer, which returns working volume to the vessel. Second, at equal thickness the shell runs colder and heat loss drops correspondingly. The board is also lighter: our standard grade has a density of 220–280 kg/m³, so a thinner lining of lighter material meaningfully reduces total lining weight.

Where Calcium Silicate Still Makes Sense

Calcium silicate remains a reasonable choice where mechanical load-bearing is required in the insulation layer itself, where budget dominates the decision, and where the extra lining thickness costs nothing because the vessel is already built. Microporous board has low mechanical strength and must be protected from direct flame impingement and abrasion by a working refractory layer — the same rule we state on our product page. It is a backup insulation, not a working lining.

Selection Guidance

Choose microporous board when lining thickness or weight is constrained, when shell temperature or energy loss targets are tight, or when you are debottlenecking an existing vessel without enlarging the shell. Stay with calcium silicate when the insulation must carry mechanical load or when first cost is the only criterion. For a thickness calculation on a real ladle, see how to calculate microporous insulation thickness for steel ladles, or send us your lining drawing for a free sizing review.