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Fiberglass Batt Insulation Often Underperforms

February 26, 2016

Any good insulation contractor will tell you that heating and cooling drains more money from the budget than any other energy usage. They will also explain that an energy efficient "building envelope" is key to keeping heating and cooling costs down. When it comes to insulating a home, it's known that not all products are created equal, and not all installations deliver peak performance. For example, just boosting up the R-Value to the maximum will not necessarily ensure the best long-term performance. Take fiberglass batts, for instance. They are sure to underperform when installed poorly. And this is especially true when a homeowner decides to undertake a DIY project. On the other hand, fiberglass batts do perform better when professionally installed - they are cut correctly; installed strategically; and adapted properly to their space. More than that, a professional install will ensure that everything is to code, and that no shortcuts have been taken. It's the only way to ensure product performance. Even with a professional installation, fiberglass batts can be problematic. Some issues are quite typical, while others can actually compromise the integrity of the insulation and downgrade R-Values. A good contractor will underline the pros and cons for a homeowner and offer alternative product options and recommendations for the project. But nothing beats being a well-informed consumer - it makes for a better understanding of the issues at hand, and it sets the stage for a better contractor relationship.

Sizing and Cutting

Unless fiberglass batts are cut and trimmed to perfectly fit a space, they will not perform. A perfect fit means having absolutely no gaps and no compression (both will negatively affect performance). Irregular spaces are also difficult to properly insulate with fiberglass batts - they just don't fit. In the end, even if the insulation product is rated at R-15 it will not be performing at R-15.

Junction Boxes

Whether it's in the attic or the basement, electric junction boxes are ever apparent. The professionals consider these to be a "thermal liability" since heat will easily flow through these. Here again, the fiberglass batts fall short - they just cannot fully insulate around junction boxes. And as much as this seems straightforward and simple to resolve, even an expert install can fall short.

Air and Moisture

For professional insulation contractors, fiberglass batt insulation does not suitably address the air and moisture issues that are prevalent in attics or basements. This is particularly true when it comes to "air leakage". Simply put, batts do not seal a space, and therefore, air movement is not fully curtailed. It's similar with moisture control - fiberglass just isn't able to stop moisture collection.

A Wet Environment

Wetness is the enemy of fiberglass batt insulation. When batts get wet they lose their product integrity as well as their R-Value. Undetected, the batts can deteriorate, requiring removal and reinstallation. In a worst case, a wet environment can also allow mold to grow. Suddenly, this isn't an insulation issue any more, and will likely require the special services of a mold removal professional.

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