InsulSizer: Insulation Calc

Stop the sweat. InsulSizer gives you the minimum insulation thickness that keeps a cold pipe or duct above the dew point - in seconds, on site, with no internet connection.

Built for HVAC and mechanical engineers, contractors and estimators who need a defensible number fast.

THREE CALCULATIONS
- Condensation control: enter operating temperature, ambient temperature and relative humidity, and get the minimum thickness that holds the surface above dew point, the resulting surface temperature, and your margin, colour-coded at a glance.
- Heat loss and gain: enter a thickness and get heat flow per metre or per square metre, the outer surface temperature, and an automatic condensation-risk flag.
- Personnel protection: find the thickness that keeps a hot surface at or below a burn-safe limit, 60 C / 140 F by default.

WHY THE NUMBERS HOLD UP
- Thermal conductivity is evaluated at the real mean temperature of the insulation instead of being fixed at one reference value, and the k value used is shown with every result so you can check it against a data sheet.
- Jacket emissivity is a first-class input. Bright metal and painted or PVC finishes behave very differently, and on a cold line that difference changes the required thickness.
- Surface temperature is solved iteratively, because both the conductivity and the outer film coefficient depend on it.
- Results round up to standard nominal thicknesses, so the answer is something you can actually order and install.
- Steady-state heat transfer follows the ASTM C680 approach; dew point uses the Magnus/ASHRAE saturation relation.

MATERIALS AND GEOMETRY
Elastomeric, fiberglass, mineral wool, polyisocyanurate, cellular glass, phenolic foam, calcium silicate, XPS and EPS. Pipe from 1/2" to 8" NPS using standard outside diameters, plus flat surfaces for ducts, tanks, vessels and equipment.

WORKS THE WAY YOU DO
- Fully offline. No account, no sign-up, no tracking, no ads.
- Metric or imperial, set independently: C or F, mm or inch, W/m.K or Btu.in/h.ft2.F, W or Btu.
- Still air, or enter a wind speed.
- Warns you when the ambient air is so close to saturation that no practical thickness will keep a cold line dry.
- Available in English, Spanish, Chinese, Portuguese, Japanese, Korean and Vietnamese.

One-time purchase. No subscription.

InsulSizer is a calculation aid for preliminary sizing and field estimation. Published material properties vary between manufacturers and grades, and real installations are affected by joints, supports, jacket condition, moisture and workmanship. Always confirm the final specification against the manufacturer's published data for the product being installed and against the governing project specification and local code.