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Steam Piping Insulation


I have just replaced my 70+ years old steam boiler - a local contractor appears did a knowledgeable and quality job. However, the job is not completed because I decided to install new and missing piping insulation by myself, to save money on the labor.

Can anybody advice where to find table for selection of insulation thickness for steam piping? I will need to install fiberglass or mineral wool pre-formed pipe insulation. So far, I cannot find information with clear data and I am not sure if the local insulation suppliers would be very particular on the data.

I do have calculation software by Armacell (Armaflex), but I am not sure what is the definition of surface temperature. Is it of pipe or insulation? Also, it does not appear that Armacell makes mineral insulation.

Please share your knowledge.

Thank you.


  • Thad English
    Thad English Member Posts: 152

    As a homeowner who has done this project, I can tell you that 3/4" fiberglass pipe insulation is the way to go. Folks have found it at Lowe's. I have seen it at the HD. A plumbing supply house most likely will carry it. You need to know the diameter of your mains since this stuff is rigid, and covered with a nice foil-backed paper. It is split down one side so you can slip it over then pipe and it also has a glue tab to make sure it stays put. It's kind of pricey, but it pays for itself over one heating season.
    Good luck,
  • Zorian Pinsky
    Zorian Pinsky Member Posts: 21
    Insulation Thickness


    Thank you for the input. However, a chart that I found indicates that thickness of fiberglass insulation should be 1 1/2" for pipes 2" and below, 2" for 2 1/2" and above pipes - all for steam carrying. My pipe size range is 1 1/2" to 3".

  • Thad English
    Thad English Member Posts: 152

    I have seen the same chart, but finding that 1.5" insulation for a reasonable amount of $$ was a real challenge for me here in Philly. I went with the 3/4" and have had good performance. I do like to have a little heat in the basement so it works out fine for me.
    Good luck in your quest for the thicker varieties.
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