Blown Cellulose Insulation: Frustrations and Advice

By Vernon Trollinger, December 11, 2009, Energy Efficiency, Green, Save Money

I was looking for a new tool to cut circles in ductwork sheet metal when I stumbled onto   It's the adventures of a couple working on their first home: a lovely Victorian Italianate in upstate New York.

One of the sections they cover is blowing cellulose insulation .  Cellulose insulation is made from recycled newspaper with borate added to increase its resistance to fire and insects.  Cellulose insulation is “dense-packed” into the wall cavities to increase thermal resistance and seal air leaks.

If your home is older and has little or no insulation in the walls, and you are thinking about saving money with the Federal Energy Efficiency Tax Credit, this on-line journal is something you might want to check out.

Most installations use the two-hole method: Two holes are drilled in the area between two studs ("stud bay") – one half way up the wall and one towards the top of the wall. (You can be inside or outside for any installation in your walls).  As the material goes in you also have to allow the machine’s air pressure to escape, otherwise the pressure will continue to provide resistance to the material trying to exit the hose.

Cellulose is then added with a hose and nozzle through the lower hole. The cellulose falls to the bottom and slowly fills the wall cavity until it reaches the level of the lower hole. The nozzle is moved to the upper hole and the process is repeated to fill the entire cavity.

The problem with the two-hole method is that the cellulose is not packed to a tight enough density to prevent settling and airflow.

The dense-pack, or wall-tube, method is best because it eliminates settling by filling the stud bay from bottom to top. The wall tube is a rigid hose connected to the blower hose nozzle.  The wall tube is then inserted into the top hole all the way to the bottom of the stud bay.  One commentor recommended a 90 degree pice of pvc tubing for the connection.  Switch on the blower and retract the wall-tube as the cavity fills. As the machine boggs down you know to retract the hose until you top it off.

If you've never had the pleasure and are considering it, this is a nice resource.  They also talk about their mistakes and their solutions:

Lessons Learned:

*  Prepare for a big mess. Put plastic up in your doorways and tape the seams so you can keep the mess in one place. Put a big tarp under the hopper for easy clean-up outdoors.

*  It’s more time consuming than you might think. We did 4 outer walls and one ceiling in about 8 hours. We had a major setback with the clogging, though.

*  It’s definitely a two-person job. Three would be ideal, since it was hard to hold the hose in place and run the remote control at the same time. It took two hands to hold the hose steadily against the wall for that long.

*  Break your cellulose up into very small chunks, the smaller the better. The machine doesn’t agitate and break them up all that well.

*  Watch your hose closely so you can catch it clogging before the whole thing is packed up. Once it’s packed, it’s a major pain to get cleaned out.

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