Using bubble wrap to minimize moisture in settee lockers?

[RhythmDoctor]

I'm trying to minimize moisture buildup in my settees. When I acquired my boat there was some minor mildew on the orange life jackets stored there. Fortunately I have many better PFDs from my other boats, but I want to keep them mildew-free.

Conventional wisdom on this seems to be to increase ventilation in the settee lockers to prevent moisture buildup, and I often see boats with vent grills added there. But this past April I noticed that the more I ventilated the worse the moisture got. We had an unusual heat wave in April with temps and humidity in the 80s. Then I realized that the moisture was only occurring below the water line. Water temp at the time was about 50, so it was clear to me that the moisture was condensation from the large temperature difference.

I'm not sure if those conditions are representative, but it did lead to some contrarian thinking on my part. Since my boat has a bone-dry bilge (no packing gland because of an outboard), it seemed that I could minimize condensation by insulating the settee lockers. I wanted a cheap, disposable material for insulating the inner hull, so I taped in some leftover bubble wrap (the type with the 1" dia bubbles). Of course it would help to insulate the top also, so I now leave the settees closed when I leave the boat, with the cushions down to further insulate. So far I have had no moisture on the materials that I stored. When I check under the bubble wrap, there's no moisture there either. So either the climate conditions have been just right, or I've made a significant improvement.

How does this match up with all of your experience?

FYI, I also posted a comment about a miniature dehumidifier here.

[GraemeInCanada]

I have to say that I think that is a great idea.. I can think of a few uses for that. I wonder how it stacks up against a flexible insulation material like some kind of foam or something. Bubble wrap sounds cheap and easy though, I like it.

[RichH]

Youll probably increase the mildew formation due to the 'localized' increase of humidity between the bubble wrap and the hull --- unless you completely seal the bubble wrap to the hull to prevent intrusion moisture AND mildew spores.

Mildew propagates from spores which easily are carried on the smallest air-currents. So, if you are plagued with mildew it means that there is probably a massive growth of mildew on your boat somewhere hidden that is issuing the spores - all the dark and damp 'undersides' of flooring, ceiling, panels, bilge walls, etc. that NEVER get cleaned.

To lessen mildew in such places you can use a modern version of what our ancestors called 'whitewashing'. Take a modern highly caustic liquid detergent, spray it onto those surfaces (not painted or bare wood) and let dry (dont wipe). Mold spores are inactivated by such 'caustic' surfaces. One of the best of such 'caustics' Ive found is a fairly common product containing sodium silicate - "Tuff-eNuf", sold in many 'boat stores'. Caustics also DISSOLVE and liquify the mildew cells - makes for SAFER and easier cleaning; as, mildew can be very dangerous to your respiratory system when 'disturbed' while cleaning.

Chlorine bleach only kills the cells; thus, leaving the cell debris on the surface which can become the nutrient source for other (some dangerous) mold/mildew species.

[RhythmDoctor]

Originally Posted by RichH

Youll probably increase the mildew formation due to the 'localized' increase of humidity between the bubble wrap and the hull --- unless you completely seal the bubble wrap to the hull to prevent intrusion moisture AND mildew spores.

The bubble wrap has been in place for over a month now, and the effect is exactly the opposite of what you say. The inside hull surface went from always damp below the waterline (due to its temp being below the dew point) to completely dry everywhere, including between the bubble wrap and the hull surface. The reason for this appears to be that the bubble wrap eliminates the abrupt temperature gradient that causes warm moist air to contact a hard surface below the dew point. I will continue to monitor this, but basically if there's no moisture there will be no mildew growth.

Prior to putting in the bubble wrap I did a thorough process to kill and mechanically wash any potential mildew from all accessible hard surfaces in the boat. I also did some special off-site cleaning of the cushions. All of this was precautionary - there was never anything more than a few black spots on a couple of PFDs that appeared to be stored in constant moisture. It's rather presumptuous for you to suggest that I am "plagued" by mildew and water intrusion without even seeing my boat. I'm just trying to take an overall good situation and make it better by eradicating the last apparent source of moisture in my lockers.

Note that my results may be unique to boats with no moisture in the bilge. For other boats with packing gland and other sources of water in the bilge, closing off the circulation under the settees may cause moisture buildup no matter how well you insulate below the water line.

[scottyt]

do a search on reflectx or something like that. its a bubble wrap with small bubbles and a tough coating with mylar on one side

[mitchbrown]

Hi Doctor

This is a great idea, I will try it as well.
Im sure since the moist air is unable to circulate next to the cool hull wall that is why it stays dry. Bravo!

Mitch

[RichH]

Originally Posted by RhythmDoctor

It's rather presumptuous for you to suggest that I am "plagued" by mildew and water intrusion without even seeing my boat.

I gave you a myco-biologically correct response with NO inference to your cleanliness preferences, etc. Im sorry that I wasted the time to give you the advice.

[hellosailor]

RD, this is a case where "both sides are right" even if that seems contrary. When moist air hits a cold surface, you get condensation. If you provide insulation (even bubblewrap) that causes the "cold" boundary to be shifted into the insulation...then the moist air can't reach the boundary and you don't get condensation.

Unless the boundary is still exposed to SOME lesser amount of air, in which case it forms a nice protected niche for the mildew to start growing in. So in theory, you want the sealed insulation to be sealed to the hull, so no condensation can get trapped and start mildew back there. In practice, you may have enough insulation and a "good enough" fit so that you get little or nor condensation and mildew growth. All depends on how lucky you are, how much moisture and air movement there is, the phase of the moon and all that good stuff.
Turn your back on it for a month--and you may find a nasty surprise growing in there. So using a troweled-on adhesive and sealing the insulation to the hull, might not be a bad idea. Except bubble-wrap eventually gets popped, so a closed-cell foam insulation might be a more permanent solution. Your choice, whatever compromise works.
Mildew, like roaches, is awfully good at surprising you.

[bljones]

I have been able to get a handle on the moisture issues in the below deck lockers in my boats with a few of these:



Silica Gel Dehumidifiers - Lee Valley Tools

No rust, no mildew, no mould. Reusable, durable and no energy usage.

[RhythmDoctor]

Originally Posted by RichH

I gave you a myco-biologically correct response with NO inference to your cleanliness preferences, etc. Im sorry that I wasted the time to give you the advice.

Your advice is helpful to both me and others here. In my haste I made a poor choice of words. That's not a valid excuse - I apologize for rubbing you the wrong way.