Insulating with spray foam?

[Cpt Mark]

Hi all,

Winter is coming and it gets cold here in Portland OR. Ice on the river cold.

My catamaran has a fiberglass liner between the outside and inside of the boat with a 1-2 inch or more space in between. By removing the hatches I have great access to this area.

So much heat is lost because the boat has no insulation and conversely, when it's hot outside....it's hotter inside'

I'm thinking of filling the area with closed cell spray foam. I'd need to stay away from the compression post as the mast wiring goes down there. The rest of the wiring goes through a channel that wouldn't be filled in.

Has anyone done this? Any thoughts about this idea, good, bad, indifferent?

I have a reverse cycle heat pump but I can't use it for the coldest 2 months of the year because the water temp is too low. So keeping heat in the boat as a liveaboard is a real issue.

[Bill O]

Only used the spray foam to repair portions that were originally sprayed on the interior of our hull.

If you are going to spray in into an enclosed space (between hull and liner) be careful of over expansion, otherwise it could bulge out or even crack the liner. They do make different foams w/different expansion characteristics, so possibly choose one for windows that doesn't over expand/create too much pressure.

Still there is some technique to using the foam. Basically fill the liquid into the void 1/2 way or less and it will then expand to fill the rest. Would practice on something other than the boat if you've never used it before.
If you are doing it in an area where no one will see, you could add expansion relief holes to allow some of the excess foam/pressure to escape.
The spray foam could work, but can't stress enough, be careful. Also wear eye protection, nitrile gloves and put paper down in/around the work area to catch foam drips/splatter. (The stuff is almost worst than working w/5200)

Can you fit foam boards in the voids?

[wingssail]

Originally Posted by Cpt Mark

Hi all,

Winter is coming and it gets cold here in Portland OR. Ice on the river cold.

My catamaran has a fiberglass liner between the outside and inside of the boat with a 1-2 inch or more space in between. By removing the hatches I have great access to this area.

So much heat is lost because the boat has no insulation and conversely, when it's hot outside....it's hotter inside'

I'm thinking of filling the area with closed cell spray foam. I'd need to stay away from the compression post as the mast wiring goes down there. The rest of the wiring goes through a channel that wouldn't be filled in.

Has anyone done this? Any thoughts about this idea, good, bad, indifferent?

I have a reverse cycle heat pump but I can't use it for the coldest 2 months of the year because the water temp is too low. So keeping heat in the boat as a liveaboard is a real issue.

I actually tried to use spray foam but the amount in a spray can is too small to do much good. I was able to buy 2-part urethane foam in liquid form. This was a dramatic increase in the amount of foam. You mix it and have a couple of seconds to pour it into the space. Yes, I said a couple of seconds! You must be prepared and work fast, and mix small quantities.

[Spot]

We have a family friend who does spray foam insulation as a business. Has anyone employed such a person to insulate a boat?

[psk125]

My father's center console outboard had poured foam under the sole- about 8" or more deep. Wonderful... until water soaked into it. It acted like the foam that's used in floral arrangements, turning the entire lower hull into an enormous sponge. It must have added more than 1000 pounds to the boat. To remove it I had to cut through the sole and dig out the foam with a spade. Each shovelful weighed about 15 pounds and dripped water. I replaced it with blocks of styrofoam, cut to fit, and then rebuilt the sole and glassed it in again. So... poured in foam might work, but be careful that the one you use DOESN'T absorb water.

The spray foam insulation guys that do houses generally come in and spray the open walls to fill in the spaces between the studs. They then shave off any "overfill" and then the sheetrock gets applied. On the OP's boat the liner is already in place so the foam would have to be shot in the space between -- like the sheetrock was already there in a house. Not likely easy to do. Steel boats often get sprayed insulation, but it's done before the liner (actually called ceiling, on a boat) is installed, while the boat is being built.

[SV__Grace]

I recently added insulation between our deck and ceiling panels using flexible foam boards with spray foam to fill voids.

A can of spray foam doesn't cover much surface area and is generally not used for large spaces. The expandable foam is really hard to control unless the space is enclosed.

I've seen YouTube videos of guys insulating using regular residential fiberglass rolls, which should work.

For open fiberglass areas you would need to install cover panels, which would enhance the look as well as comfort.

[foufou]

I have used two part polyurethane foam and do not recommend it. As was mentioned it does absorb moisture; a lot! I had to chip mine out and toss it int e garbage. And it can over expand and wreck things. I know! There are other epoxy based foams that may be more appropriate. Or bubble packing, or? Good luck. F

[winjamerk]

We used to live aboard a 40' mono with a Webasto diesel [liquid model] heater for primary heat source and electric radiator during less cold times. We also had horizontal 1-1/2" wide thin strip planking along most of the hull in the salon and berth areas including in some storage lockers. The wood strips were about 1" away from the hull. A trip to the hardware store & purchased 50' rolls of the aluminum foiled bubble wraps which were about 1/2-3/4" thick and 12" wide were slid down from top plank to as far as it would go along the hull. Also did additional in any accessible areas overhead. Immense difference in heat loss and was cooler during the summer. Also reduced moisture near cushions/mattresses. We also had opening ports and hatches with screens and cut-fitted clear thick mil plastic sheeting from the inside. These sheets were cut to extend about 1" beyond the opening when the port lite or hatch screen was closed or put back into place. No mil plastic was touching the exterior, keeping the 2-3" airspace. Virtually eliminated condensation and stayed bright inside. Saved these cut pieces and folded away for the next winter season. Any hardware store will have these readily available. Please keep air flowing 24/7 with dorades and fans.

[TBear60]

Two big concerns with spray foam is 1)filling too much into a small space and 2) using a very dense foam. Those who professionally spray foam into homes will caution you that to fill a wall cavity is tricky at best (I know, I asked for my house).

When they fill the walls in a house, there is only the outside surface in place; the inside drywall in not in place so the foam expands away from the outside towards the inside of the house! Then, after the foam has stopped expanding, the foam is trimmed flush with the inside level of the studs and the drywall is installed last.

Obviously denser foam, 2 lb vs 1lb, has more insulation properties, but it will also exert a greater force on the sides of an empty cavity.

Putting in too much is the same as putting in too dense of a foam. Tricky at best according to Pro's I've spoke to.

Good luck; Good Sailing!

[Matt Johnson]

We used Handi-foam slow rise to fill a cavity between the fridge insulation and the hull. I drilled a series of 3/8" holes in a grid pattern through the fiberglass fridge liner to get full access to the area. I started on one end, slowly filled through the first hole, waited for it to came out the next hole, and went to that hole and filled.

The slow rise puts much less pressure on the surface - no bulging bulkheads or anything - and it allows you to control the coverage better. I then filled the holes with fairing and gelcoat. This could easily be done with a hull liner.

Matt

[Mithril Bham]

I've heard foam is a fire hazard. Is there any true to this?

[Grattaway]

polystyrene will become very heavy when water logged - polyurethane not so much
both toxic and flammable if burned

One alternative could be plastic beads such as you can buy for a bean bag - you could blow these into a cavity. We use these for insulating tubes that go through freezer floors or where we want to put temperature probes into frozen spaces -they are a pain when not confined though

You could probably blow other insulation products into a space as well - chopped fibre or wool
Good luck

[boden36]

I can testify to the force of expanding two part foam - I filled some hollow seats in a dinghy and nearly blew the thing apart!
If you are mixing the two parts, refrigerate them first and they will be slower to react - this gives you more time to pour the foam.

[Jack C]

There are different types of spray in foam. Use the closed cell type. Then you wont get mush when water gets in. There are also the foams that dont apply high pressure. Used around window frames. The dont expand as much and only fill narrow areas. Not good for large areas because they have limited expansion and I dont know if they are closed cell.

My thoughts are use closed cell with careful application so as to not exert too much pressure. Leave holes for expansion. Getting it out later will be difficult or impossible.

For roofs they typically use open cell so that roof leaks can be detected. Closed cell in kneewalls.

To prevent condensation NO space between hull and insulation is critical. Otherwise moist air gets in and condensation happens. If its a steel boat it will rust from the inside.

Where you have easy access to the hull, we use 1 cm closed cell neoprene type foam, glued to the hull with contact cement over ALL the surface. Solves the condensation problem. Then other insulation as needed.

[R.Boyd]

Sorry to be so late reading this post. I worked for a foam contractor years ago and what you need is a “pour” foam. It has a slower reaction time and slower rise time, allowing it to fill the cavity. It’s not a product you can buy at a home center so you’d need a contractor to do it.