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Ask Mr. Tight-Watt: Wet-blown Insulation  Smart Choices Archive

Ask Mr. Tight-Watt: Wet-blown Insulation

Reputable contractors know how to install wet cellulose insulation.

Ask Mr. Tight-Watt

Question: I have talked with some others and have a concern about using the wet-blown insulation. The complaint is it will be too wet and produce mold in the house before it dries. Is this true or what needs to be done to make sure it will not happen?
—John, a Smart Choices reader

Mr. Tight Watt asked Bill McAnally, energy efficient building expert, to answer John’s question.

Bill's Answer: When using a wet blown cellulose product, the key is proper installation. Installers are able to precisely place the material in the cavities with only the needed amount of moisture, ensuring the product is the correct density and has the correct moisture content.

If the insulation is too dry, it will fall out of the cavity. If it’s too wet, the insulation might either fall out or may remain in place but take a long time to properly dry. The product should be around 15% moisture content or even less, according to a major cellulose manufacturer, before it is covered with wallboard.

Depending on the drying capacity of the surroundings, it can take a few days to even weeks to properly dry. A surface test is not enough; you must check the center of the cavity and against the exterior sheeting.

Caution: To dry the insulation more quickly,use electric heat or de-humidifiers. Using propane or kerosene heat only adds moisture to the air.

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