Closed cell
To answer your question, yes foam does lose its insulation value when it gets wet, but not 100% of it. And no, it will not dry out.
Short and sweet answer above. To expand on it a little bit - expanding foam (or great stuff or whatever it's called in your particular neck of the woods) is in no way shape or form going to stop water from getting into anything. It, by itself, is not waterproof, and water will eat it.
Styrofoam is an excellent material because it is lightweight and easy to cut and shape. However, it is not waterproof and can be damaged by water.
Since open-cell foam is more water permeable than closed-cell, once can incorrectly assume that open-cell foam will result in moisture problems. Open-Cell does not wick moisture out of air, or wick water like sponge. Water will only penetrate through the foam with pressure (i.e. submersion, flooding etc.).
Closed-cell foam is a top choice for keeping moisture out of your home. It's different from open-cell foam because it doesn't let air or water through. This makes it great for stopping leaks and preventing water damage. Closed-cell foam is special because of its density and structure.
In cases of severe water intrusion, such as a burst pipe or a flood, water will exert pressure on the foam. This pressure can cause the foam to break apart, allowing the water to flow through it. However, the foam itself does not absorb water – instead, it may be damaged or displaced by the force of the water.
While it is water resistant, it's not waterproof. Over time, it will absorb moisture from rain, snow, or spills. Extra water may also be stored causing mold and mildew growth. In addition, there are also a handful of solvents that can melt or break down polystyrene .
If your project is a floating dock or swim platform on a private lake or river, then un-encapsulated EPS will make a very durable and buoyant float. A single block of 1 lb density EPS 12” x 24” x 48” will float 440 lbs.
Directly against electrical wiring or fixtures: Spray foam insulation should not be applied directly against electrical wiring, fixtures, or recessed lighting unless they are rated for contact with insulation. Contact with insulation can cause overheating and pose a fire hazard.
Latex foams are typically “open cell” and, as a result, can absorb water.
Product information
This 750ml expanding foam filler by Gorilla Filler is perfect for weatherproofing and sealing gaps. It expands to fill voids, providing an airtight and waterproof seal.
It is known as open-cell due to half its cells being open. However, this form of expanding foam is not water-resistant or waterproof whereas closed-cell foams are. Also known as polyurethane foam, the cells are interlocked and this prevents any air or water from getting through.
If your insulation has become wet, remove it as soon as possible and replace it with new insulation. Wet insulation can lose its effectiveness and can pose health risks.
Mattresses aren't designed to get wet, particularly those made from especially memory foam. Your mattress won't dry quickly, and if it stays damp for too long because of your cleaning efforts it can start to smell or even develop mildew. That will be worse than the situation you're dealing with now!
Explanation: When water is poured into a Styrofoam cup, the cup retains its structure because water does not react with polystyrene, the material Styrofoam cups are made from. However, when gasoline is poured into a Styrofoam cup, the bottom of the cup dissolves, causing the gasoline to leak out.
Properties of Styrofoam
We use Styrofoam to make drinking cups and insulating materials, as it is a poor conductor of heat and is insoluble in water. Styrofoam is a non-polar molecule – the electrons are pretty equally shared among the bonds in the molecule.
To answer shortly: YES, spray foam can resist water from entering your home. The air-tight sealing it provides helps keep moisture from seeping inside and damaging your property.
Open-cell spray foam is more porous than closed-cell foam, so it may absorb water if it gets wet. This can lead to decreased R-value and, over time, the potential development of mold or mildew if the moisture is not properly addressed.
It absorb water slowly but can take a lot. Eps and xps are closed cell foam. Each cell don't take water if not open. In eps there is more or less space between cells that can take water, lot of water by succion when foam enclosed and pressure difference between outside and inside.
So, if it is waterproof and unsinkable, how can it become full of water? Cold water will not penetrate the closed cells of extruded polystyrene, called Styrofoam by Dow Chemical and other things by a number of other companies. However, hot water vapour under pressure can slowly saturate insulation panels.
Dryfast foam is the best foam for use in outdoor cushions. It is porous, so it allows water to flow through without being trapped. Can Dryfast foam be washed? Dryfast foam can be rinsed with water when needed.
The foam will naturally break down and dissolve back into the water. Foam can contain high levels of contaminants that may pose a health risk to humans and pets. If you touch foam, wash your skin with soap and clean water as soon as possible.
Hawaii Construction Foam insulation will absorb a maximum of 2-4% by volume when exposed to the testing specified by ASTM C578. The ASTM C578 water absorption requirement is determined by submerging a 12” x 12” x 1” piece of insulation in water for 24 hours.