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What Happens if Insulation Gets Wet During Construction

During construction, building materials that are supposed to be on the interior of a house are often temporarily exposed to the elements. When materials that need to stay dry get stuck in the rain, problems may ensue. 

When wet, insulation is dangerous and ineffective, but it’s not necessarily irredeemable.

If insulation gets wet during construction, it cannot be installed while still wet. In some cases, the insulation can be dried out again. Other times, it is necessary to purchase new insulation if the water content is too great or if the insulation has been damaged.

Wet Insulation Will Not Work

Wet insulation will not work properly if installed in the walls of a home.

When insulation made of materials such as fiberglass, foam, cellulose, and mineral wool becomes waterlogged, it loses its thermal resistance. In other words, wet insulation is no longer good at insulating.

There’s science to back up this phenomenon. Water is a better conductor of heat than air. When water replaces the air pockets inside insulation, it makes the insulation better at conducting heat as well. 

The insulation will not be able to properly regulate the temperature of the building while it is wet.

If this were the only downside of using wet insulation, the simplest solution would be to continue using the wet insulation and simply allow it to dry as construction continues around it. However, this would be a grave mistake.

Wet insulation is a structural hazard and a health hazard. The moisture in the insulation will naturally travel to the bottom, soaking the wooden framework of the house. This can cause the wood to rot and become soft.

Wet mineral wool insulation

The dark, damp atmosphere of wet insulation is also the ideal breeding ground for mold and bacteria. The insulation and surrounding construction will later have to be replaced as mold and bacteria are health hazards to inhabitants.

Wet insulation is not something that can just be covered up and forgotten about. It is an issue that needs to be solved before the insulation is used in order to prevent larger problems and expenses down the line.

Dealing With Wet Insulation During Construction

Let It Dry

The first and more cost-effective solution is to let the insulation dry. Let me be clear that the insulation must be fully dry before it is installed. Even slightly wet insulation that is installed in a home can cause the issues that were previously discussed.

There are most likely other projects that can be done in the meantime while you are waiting for the insulation to dry. Finding an alternative project to do can help keep a tight schedule running smoothly.

In cases where the insulation is only damp and not completely soaked through, letting it dry is a safe bet that won’t require too much extra time.

Being able to dry out the insulation again after it has become wet also depends on the type of insulation. Mineral wool insulation is water-resistant and holds its shape when in contact with water. 

On the other hand, cellulose and fiberglass insulation soaks up water and compresses. These types of insulation will be harder to dry out again.


  • Cost: letting the insulation dry saves you from having to purchase new product.
  • Moisture level: this option is better suited for insulation that isn’t soaked all the way through, but maybe the first centimeter or two is damp.


  • Safety: Insulation that isn’t fully dry all the way through will still be a structural hazard and health hazard.
  • Time: Waiting for insulation to dry can bump back a construction timeline.
  • Weather: If the weather continues to be wet, the insulation may not be able to dry out.
  • Unseen damage: Water inside the insulation could have caused damage that is not seen by the bare eye. The insulation may never be as effective as it should be.
  • Moisture level: insulation that is fully soaked will take a very long time to dry.

Replace It

Sometimes letting the insulation dry out is not an option. It may be necessary to replace it instead.

Man installing mineral wool insulation

As the saying goes, “Better safe than sorry.” It can be hard to tell whether or not the insulation has truly dried all the way through, and even just a bit of moisture in its center can cause problems later on.

If the insulation has been wet for an extended period of time, there is a possibility for mold spores to find their way inside and begin spreading. Installing moldy insulation will lead to poor air quality in the building, which has serious health repercussions.

Additionally, construction timelines may not be able to wait for the insulation to dry out. If there is nothing to be done while the insulation dries, people are losing out on time they could be finishing the building project.

Of course, replacing the insulation is the more expensive option out of the two. It’s not cheap to buy all new insulation, but it’s even more expensive to install a damaged product only to later have to rip it out and create more problems in the meantime.

Building insurance may or may not cover the damage caused to the insulation. Water damage caused by neglect or faulty installation will not be covered, but in cases such as extreme storms and hurricanes, you may have better luck.

Since the insulation has not been installed in the home yet, homeowners insurance will not apply. If you have building insurance specifically for damage that occurred during construction, you may be able to get insurance to cover some of the cost.


  • Peace of mind: You don’t have to worry that the insulation may not have been completely dry.
  • Time: Buying new insulation will prevent wasted time while waiting for the insulation to dry.


  • Cost: Buying new insulation is expensive and may not be covered by insurance.
  • Time: You may not be waiting for the insulation to dry anymore, but it takes time to order and receive new insulation as well.


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