What Happens When Metal Building Insulation Becomes Wet?

March 3, 2021

This is a question that gets asked very frequently, and in most cases, the next question is, “Does the insulation need to be replaced?” The most common response to the original and follow up question is, “It depends”. So, we are going to take you through how insulation typically becomes wet on a job site, what to do if/when it becomes wet, and what preventative measures should be taken to reduce the chance of the insulation becoming wet.

How Did The Insulation Become Wet, And Was The Water Clean Or Dirty?

Clean Water

The most common reason is a rain storm. When (MBI) fiberglass insulation becomes wet from rain or another clean source of water, it can temporarily lose a substantial measure of its thermal resistance (R-value). This is because the spaces created by the glass fiber that are filled with air will now be filled with water. Water is more conductive than air, which reduces the thermal value of the insulation. The water may also reduce the thickness of the insulation as the glass fibers are not able to support the weight of the water. Reduced thickness also will reduce the thermal value.

This loss of thermal performance may only be a temporary situation. As soon as the water evaporates and the insulation becomes dry again, it can regain its original performance level. In addition, since fiberglass insulation does not absorb water, the insulation fibers will not be structurally altered or permanently affected in any other way, meaning it will likely return to its original listed thickness and thermal value. Insulation that becomes wet with clean water like condensation or rain water can likely be left in place and allowed to dry. Once dry, it should contain no more organic material or contaminants than insulation that was never wet.

Therefore, as long as the insulation is allowed to dry from clean water exposure and it retains its original thickness, it does not need to be replaced.

Please note, however, that if the water infiltration and saturation is substantial enough to mat down the fiberglass insulation to a greatly reduced thickness, the insulation will not likely regain its original shape. If this occurs, and the insulation cannot be fully dried and/or cannot recover to its original thickness, it will not retain its original R-value and should be replaced with new insulation.

Dirty Or Contaminated Water

Another common example of insulation becoming wet is if the insulation was resting on the ground at the jobsite during a storm. Due to a storm, large puddles of contaminated water can form around the insulation. The contamination can be from dirt, mud, oil, etc. The issue with dirty and contaminated water is that when it evaporates, it can leave deposits of foreign materials or other contaminants in the insulation. These may decrease the R-value, and more importantly, could also give mold and/or mildew a food source and a place to propagate within the insulation. This growth and/or odor may also be transferred to connected building materials. For this reason, if the condition or contamination of the water is unknown, it is highly recommended that the insulation be removed, disposed of, and replaced with new insulation.

Therefore, any insulation that becomes wet with contaminated water should be replaced with new insulation.

How Do I Make Sure The Insulation Does Not Become Wet On A Jobsite?

While there are never any guarantees when it comes to Mother Nature, there are ways to store and/or stage the insulation to insure that the chances of it becoming wet are greatly minimized.

The best way to ensure that insulation does not get wet is to keep it covered and secured in a trailer at the jobsite, as can be seen in the picture.

If having a trailer full of insulation at the jobsite is not an option, then store the insulation on pallets so that it may be raised high enough off the ground from forming puddles or the potential flooding from heavy rains. If possible, place the pallets of insulation on concrete or at the highest elevation on the jobsite as possible.

Besides keeping the insulation off the ground, if there is a potential for rain in the forecast, placing tarps over the insulation can further reduce the chance it will become wet.

During installation, any insulation that will be left exposed at the end of the workday should be covered, especially if there is even the slightest chance of rain in the forecast. The small amount of time it takes to cover up exposed insulation at the end of the workday may be well worth the effort.