Most everyone is familiar with the pink fiberglass insulation found in many, many homes. Everyone knows the pink feline character that shows us how this stuff will keep our homes warm and our energy bills reasonable. If only he had an infrared camera, the things he'd see!

There has been controversy surrounding the effectiveness of fiberglass insulation for years mostly between the manufactures and building science experts. The facts are strong that fiberglass is poor insulation that rarely performs as stated.

In the infrared image at right (this was taken in the summer) this insulated ceiling doesn't look to be insulated at all in some areas.  The hot attic air is moving around the insulation, or more accurately the vapor retarder, rendering it ineffective. Air also easily passes through fiberglass (they make filters out of this stuff). Exposed fiberglass attic insulation is subject to convective loops and studies have shown its performance diminishes dramatically as temperature difference increases (winter or summer).

The second image shows a wall section where the studs are actually performing better than the insulation. Notice the wall is cooler (purple) than the studs (orange). This is a 2 x 6 wall with R-19 fiberglass batt insulation. Woods R value is about 1.5 per inch. Which means this R-19 wall is performing at less than R - 8!

Cellulose insulation on the other hand is not prone to these thermal or convective problems. First it does not require a paper vapor retarder. It can be sprayed or dense packed into wall and ceiling cavities leaving no voids around mechanical penetrations. Cutting and fitting batt fiberglass insulation around electrical boxes, plumbing and heating fixtures results in voids that create airways.

It has a slightly higher R value (3.8 / inch) than fiberglass (3.7 / inch). Best of all it is made from recycled materials (newspaper) and uses significantly less energy (750 Btu / lb.) to manufacture than fiberglass (12,000 Btu / lb.) or foam (33,000 - 48,000 Btu / lb.) insulations.

One potential problem with cellulose is in retrofit applications. As can be seen in the last infrared image these wall cavities were incompletely filled. Older cellulose was prone to settling, this image however is not an old installation.

Cellulose today is manufactured to eliminate settling by making the material slightly "springy".  By dense packing it in the wall cavity the material is under slight pressure and can not move. No more settling problems.

The benefits of this material over other insulations, most notably fiberglass, are considerable. Yet what usually decides what insulating material is used, initial cost, is where cellulose falls behind fiberglass. Its cost is about one and a half to two times that of fiberglass, but because it performs better the energy savings usually offset the extra up front expense.

Continually seeing air leakage and poor performance through the infrared camera lens has made it apparent to me that using fiberglass insulation is a bad building practice. In the long run using higher performing insulation such as cellulose will help make our homes more comfortable and energy efficient.

James Quarello
JRV Home Inspection Services, LLC

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