SAY NO TO FIBERGLASS UNDER YOUR HOME

CHOOSE YOUR INSULATION CAREFULLY

It is very common for our appointment center to receive calls from homeowners wanting their fiberglass insulation to be replaced in their crawlspace or basement. However, this wouldn't provide a long term solution.  The big selling points for fiberglass make it the most commonly used and recommended insulation. It is inexpensive and works in the vast majority of installation practices within the home. In fact, more than 90% of homes in the United States are lined with Fiberglass insulation. (Fuller, 2017). It is a mixture of fibrous glass that came into popularity with the declining use of asbestos. When installed properly it is safe and rests between panels, sheetrock, and plaster. However, according to manufacturing specifications, the correct installation of fiberglass, has the insulation covered on all 6 sides (as in a wall cavity). This is specified so the glass particles do not escape, and do not become fine particulate in the air of the home that are then breathed in. However, this is not how insulation is installed in a crawlspace.

The typical installation of subfloor insulation is as follows:

Insulation is placed inside the floor joists with the vapor barrier side (paper adhesive that the insulation is secured to) facing the interior side of the home. You are not to compress the fiberglass and allow it to expand completely to fill the rafter cavity. The fiberglass insulation is then held in place through the use of support wires below to secure the fiberglass insulation in place (Lipford, 2017). 

This process leaves that underside of the fiberglass completely exposed to the elements under the home and runs into a problem when we consider “The Stack Effect”. The ground takes in water during rain and evaporates back up into the atmosphere. The vapor absorbs into the fiberglass and when water weight hits, we run into more problems:

• This condensation moves up from the dirt floor crawlspace, and into the exposed fiberglass insulation. Over time this insulation retains enough moisture that it sags. Once the insulation has sagged and fallen from the rafters a few issues can occur. Fallen insulation provides an air break. The entire point of installing insulation under the floor is to prevent cold air from the crawl space from entering the home. These gaps allow that cold outside air a direct path up through the floorboards, rendering the insulation useless. 
• Once moisture has collected and breaks up the insulation, the moisture is able to reach organic material such as the paper backing of the insulation and the wood subfloor. This creates a perfect environment for mold to grow. Much of this is due to our current building methods. Homes are sealed up tight. Energy efficient windows and doors, sealed building envelopes and controlled home environments add to the stack effect. Air must have somewhere to go. It will continue to travel upward. The fiberglass insulation serves as a filter between the ground and your home. Think of furnace filters and car filters for a second. How do you clean them? You don’t, you replace them. Only you don’t replace your fiberglass insulation annually. It just continues to accumulate mold, mildew, and debris.
• Fiberglass insulation provides a warm protected area for rodents to eat, live and reproduce. According to Basement Systems, rodents are attracted to crawl spaces because they are warm, damp, and protected from the elements. In addition, they are typically near food supplies (such as trash) and are not usually monitored frequently by homeowners. Crawl spaces supply plenty of entry points for pests, including gaps between the foundation and framing, spaces under doors, penetrations for wires and pipes, vents, and tunnels through dirt floors (Basement Systems, 2017).

Fiberglass insulation may be a solid choice for many areas of the home when it is installed according to engineering specifications, but for the crawlspace, fiberglass insulation is the wrong choice. This insulation retains moisture, houses rodents, provides food for mold, and once damp provides no insulating value for your home. Before installing ineffective fiberglass insulation, review other insulating materials that would be better suited for crawlspace conditions and your home specifically.

Resources

Basement Systems (2017). Rodent Control in Crawl Spaces. Retrieved from https://www.basementsystems.com/crawl-space/crawl-space-rats.html

Fuller, J. (2017) Is insulation dangerous? Retrieved from https://home.howstuffworks.com/home-improvement/household-safety/tips/dangerous-insulation1.htm

Lipford, D. (2017). Is Hidden Mold at Home Making You Sick? Retrieved from http://abcnews.go.com/WNT/story?id=131638&page=1