Musings from a Deep Energy Retrofit: Dense Pack Cellulose Check

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This week, I’m sharing a few observations, some technical, some not, from a deep energy retrofit of my own home in Burlington, VT. Part 3 of the series

Original draft proofing, building paper held to the inside of the exterior wall, fastened with battens to the studs

Original draft proofing, building paper held to the inside of the exterior wall, fastened with battens to the studs

When I first bought this house six years ago, the walls weren’t insulated. While I intended all along to insulate on the exterior, I knew that wouldn’t be for several years.  (Sounds like a staged retrofit, to me.) I didn’t want to wait that long to start chipping away at better comfort and reduced energy use. That meant insulating the walls and attic.<sup>1</sup>

At that time I was responsible for the Syracuse operation of my previous company. There were some superb installers on staff, and a few made the drive over to Burlington to dense pack my walls with cellulose.

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The dense pack cellulose was…densely packed. It stays in place if uncovered.

And they did a great job. (Joe, Tom, Jim thanks.) Checking the walls with IR I found only a couple of anomalies, each about a square foot. One I later discovered was caused by some bunching of the building paper that had been the original draft protection when the home was built. Essentially it was building paper held to the inside of the exterior wall, fastened with battens to the studs. See the picture at right, for a sense of how this looks from the exterior (with sheathing removed). Subsequent remodeling has found they were pretty meticulous, hitting even the smaller partial bays above and below windows, for example. It two spots during the dense packing process, drilling and inserting the tube apparently cause the paper to fall away and bunch in the cavity preventing full coverage–but that’s not bad considering the total area treated.

The dense pack was, well, densely packed. As you can see here removing the sheeting and paper the insulation stays in place in its monolithic state. Same thing where I removed the plaster board in a few areas. Uncovering about 150 square feet of wall, I only found one area were the insulation didn’t have complete coverage.2 I suspect this was because the jumble of wires from a wiring retrofit created enough of a structure so the cellulose created an obstruction as it was being installed.

The only void in the insulated cavity that I've been able to find.

The only void in the insulated cavity that I’ve been able to find.

By and large, I was very impressed with the installation, and with the results. In the first phase of the retrofit, I was able to reduce natural gas use by more than 60%, and this included heating water for a family of four instead of the single occupant previous owner.

There are still a lot of empty wall cavities around the country. And more will poorly installed insulation. We can make then perform better–increasing comfort, and decreasing energy bills–with a good wall insulation job.

1The slopes of the attic where insulated with 6″ of mineral wool batts. Interestingly, the gable ends were not insulated at all. I removed the batts and reinsulated with 9″ of SPF in an extended and thermally broken rafter cavity. I also furred out the gable ends and insulated with 6″ of SPF. I share that detail in the discussion of high R-value cavities.

2Why uncover the walls? This didn’t really have anything to do with the DER. It’s just a coincidental addition/door moving project. This small areas had been hidden by a refrigerator on the inside and a stack of bins on the outside.

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About the Author:

Mike Rogers is the President of OmStout Consulting. A nationally recognized expert in residential energy-efficiency, he works with contractors and programs to scale sustainable market approaches to improving homes. More on Google+

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