Insulation K-Values Reference

Thermal conductivity (k) versus mean temperature for calcium silicate, mineral wool, perlite, foam glass, aerogel, and PIR/PUR insulation.

Insulation K-Values

INSULATION THERMAL CONDUCTIVITY (K-VALUE) REFERENCE · K-values in Btu·in/(hr·ft²·°F) at indicated mean temp | Source: ASTM C892, C547, C533, C612, manufacturer data

Material	Density (pcf)	K @ 100°F	K @ 300°F	K @ 500°F	Use Range (°F)
Calcium Silicate (ASTM C533 Type I)	14.5	0.39	0.49	0.65	100 to 1200
Calcium Silicate Type II (asbestos-free)	13	0.42	0.52	0.68	100 to 1200
Mineral Fiber (ASTM C547 Class 1)	7	0.27	0.36	0.53	-180 to 450
Mineral Fiber (ASTM C547 Class 3)	10	0.25	0.33	0.48	200 to 1000
Mineral Fiber (ASTM C547 Class 4)	12	0.24	0.31	0.46	1000 to 1200
Mineral Wool Board (ASTM C612 Type IV)	8	0.26	0.34	0.51	100 to 850
Perlite (Expanded, Preformed) ASTM C610	13	0.41	0.54	0.7	100 to 1200
Cellular Glass — Foamglas (ASTM C552 Type II)	8.5	0.3	0.42	0.58	-450 to 900
Polyisocyanurate (PIR) ASTM C591	2	0.18	0.23		-297 to 300
Polystyrene XPS (ASTM C578 Type IV)	1.6	0.2			-40 to 165
Flexible Elastomeric (ASTM C534 Grade 1)	4	0.25			-297 to 220
Aerogel Blanket (Pyrogel XTE)	10	0.16	0.24	0.32	-40 to 1200
Aerogel Blanket (Cryogel)	7	0.15			-455 to 390
Fiberglass Pipe (ASTM C547 Class 1)	4.5	0.23	0.3		0 to 450
Ceramic Fiber Blanket (ASTM C892)	8	0.44	0.58	0.95	100 to 2300
Refractory Ceramic Fiber Board	12	0.42	0.55	0.88	200 to 2000
Urethane Foam (rigid, closed cell)	2.5	0.16			-250 to 200
Vacuum Insulation Panel (VIP)	10	0.028			-40 to 150

Typical Applications

TYPICAL INSULATION SELECTION GUIDANCE

Service Condition	Recommended Insulation	Notes
Pipe ambient to 250°F	Fiberglass (ASTM C547 Cl 1) or flexible elastomeric	Flexible is simpler, higher cost
Pipe 250-850°F	Mineral fiber (C547 Cl 3) or Cal-Sil	Cal-Sil more durable for piping
Pipe 850-1200°F (CUI range avoided)	Mineral fiber Cl 4 or Cal-Sil	Use stainless jacket; watch for CUI
Cold service (≤40°F)	Foamglas, XPS, PIR, aerogel	Foamglas preferred for fire resistance
Cryogenic (≤-150°F)	Foamglas, PIR, aerogel blanket, vacuum panels	Vapor barrier is critical
High temp refractory (>1400°F)	Ceramic fiber, mineral wool (up to 1200°F)	Module / castable for >1800°F
Personnel protection only	Calculate per ASTM C1055/C1057; target <140°F surface	Often drives thickness > heat-loss thickness
CUI critical services	Cellular glass (Foamglas) — water-impermeable	Higher cost but eliminates CUI risk
PERSONNEL PROTECTION — MAX TOUCHABLE TEMP (ASTM C1055):
Flat metal surface: ≤ 140°F (5-sec contact)
Curved pipe surface: ≤ 160°F
Brief incidental contact: ≤ 180°F
UNITS CONVERSION:
1 Btu·in/(hr·ft²·°F) = 0.1442 W/(m·K)
1 W/(m·K) = 6.933 Btu·in/(hr·ft²·°F)

References

Source: Insulation_K_Values_Reference_v1.xlsx

© 2026 Inflection Point Engineering, LLC. All rights reserved. The content of this page — including calculation methods, reference data, written analysis, interactive tools, and source code — is the intellectual property of Inflection Point Engineering, LLC and is protected under applicable copyright, trademark, and trade secret laws. Unauthorized reproduction, redistribution, modification, or derivative use in whole or in part is prohibited without prior written consent.

Disclaimer. This material is provided for informational and educational purposes only and does not constitute professional engineering advice. Calculations, reference data, and methodologies are based on published standards and accepted engineering practice but are not a substitute for engineering judgment, site-specific analysis, or review by a licensed Professional Engineer. Inflection Point Engineering, LLC makes no warranties, express or implied, regarding the accuracy, completeness, or fitness for a particular purpose of any content presented here, and shall not be liable for any direct, indirect, incidental, or consequential damages arising from its use. Users assume all risk associated with applying this content to real-world design, operations, or decisions.