Port Side Main Salon: Hull Insulation

Is In! This is one one area where progress was held up waiting on hull insulation. Now the following items can be pursued:

  • Plumbing for domestic water and heating
  • Cabinet layout and structure
  • Cabinet “wall in”
  • Dinette table and settees 

Most of these items still need design work.

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Why Insulation?

The first reason is to reduce condensation on the inside surface of the hull. The second reason: to help keep heat in (our out depending on where in the world you are).

Most fiberglass production boat builders do not insulate hulls. If you spend winter time boating north of the 45th parallel, you are likely to run cabin heaters all the time. The larger the temperature differential between the inside surface of the hull and inside air, the greater the chance of condensation on the interior surface of the hull. Condensation leads to mold and mildew, which is what we are ultimately trying to avoid. Having lived aboard a small fiberglass boat one winter, we have experienced this first hand. The insulation reduces the temperature differential. Note, for steel or aluminum hulls, insulation is practically a “must”.


Our chosen material for insulation is stuff called “Armaflex SA.” It is a type of insulation often used in industrial plumbing and HVAC ducting applications. It is a black, peel-off adhesive backed, closed-cell foam kind of material. Easily cut with a utility knife, it is fire resistant and designed to withstand extreme temperatures. It comes in a variety of thicknesses (we are using the 1 inch variety). The surface is specifically treated to resist mold and mildew.

3 comments for “Port Side Main Salon: Hull Insulation

  1. Anonymous
    August 17, 2011 at 1:53 pm

    Wow that insulation looks great!

  2. August 30, 2011 at 2:02 am

    "Most fiberglass production boat builders do not insulate hulls."

    They do if they are good old fashioned Canadian boat builders from Whitby. The Whitby 42 has a cored hull above the waterline.

  3. August 30, 2011 at 1:57 pm

    I imagine canadian builders would know more about thermal insulation. Cored hulls must provide some degree more of insulation over solid glass. But our cored 28 footer suffered quite the condensation during a winter livaboard. Perhaps insulation can only do so much.

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