Dear Sir, I enjoyed your write up on using Armaflex for insolating the hull of your new FPB. Why did you use only 1/2" Armaflex on the hull for insulation? If you were planning to be in the Northwest most of the time, would you have used 1" or 1 1/2"? Did you equate an R-value for 1/2" Armaflex when compared to PF? Thanks, Dex
Hi Dex: There are a lot of trade-offs with insulation including weight, cost of materials, and labor to install. As we are only planning only to cruise during the summer months, we looked at the insulation strictly from the standpoint of condensation.
With condensation there are two factors as you probably know, temperature differential and humidity. We are based on a outside temperature of 22 degrees F/-5.5C inside ambient of 68F/20C, with a humidity of 70%. We can control the humidity, if required, with our dehumidifier to get more of a temperature differential.
Given the insulation value of the Armaflex, assuming no double glazing on the house windows, we expect a heater duty cycle of 50% in the coldest conditions.
Going to thicker insulation would reduce fuel burn and heater duty cycle, but for our purposes, and the expected temperature range (and most of the time the temperature outside would be well above our design point) we think we’re OK.
We prefer not to use blown foams as they tend to absorb moisture over time and have been known to cause problems with aluminum, if they are in direct contact. Regards – Steve
PS-my notes on the R value of Armaflex are not handy right now, but you can get the technical specs from their website.
Posted by Steve Dashew (November 30, 1999)
