What to do about miss­ing in­su­la­tion?

Canal Boat - - Back Cabin - TOOMUCH, via the CB TONY REPLIES…

The more I work on my boat the more ar­eas I find where the orig­i­nal fit­ters have skimped on, or omit­ted to in­stall, Rock­wool in­su­la­tion; I also find elec­tric cables in the most un­likely places. Short of re­mov­ing whole pan­els or cut­ting out large ac­cess pan­els, which is not prac­ti­cal, I was con­sid­er­ing us­ing ex­pand­ing foam (fire-re­tar­dant type) to fill the gaps, if nec­es­sary by drilling small holes.

I am, how­ever, con­cerned about a pos­si­ble re­ac­tion be­tween the foam and the in­su­la­tion on any hid­den cables, or does this only ap­ply to poly­styrene foam?

QCans of spray­foam are usu­ally polyurethane rather than poly­styrene and polyurethane is the spray­foam used on many boats. As far as I know it is only poly­styrene that might af­fect the

Aweb­site ca­ble, how­ever, I would make some more points. Rock­wool can ab­sorb wa­ter and one may well omit it from the hull sides in case it slips down into the bilge. If your gaps are in the cabin sides, the builders might have left a gap be­tween the in­su­la­tion and win­dow frames so when (and it is when, rather than if) the frame to cabin side seal fails, you have an area for rain­wa­ter to leak down into the bilge with­out sat­u­rat­ing any Rock­wool.

Take care that you do not cre­ate a cap­il­lary gap be­tween the foam and in­su­la­tion or fram­ing. Such small gaps may al­low con­den­sa­tion on the met­al­work to wick through the gap and stain the trim. If the foam does not make an air­tight seal to the metal cabin side, you might get con­den­sa­tion be­tween the foam and metal, caus­ing cor­ro­sion.

Be care­ful about the quan­tity of foam you in­ject and try to ob­tain a zero ex­pan­sion foam oth­er­wise the lin­ing trim might be forced into bulges as the foam ex­pands.

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