Recycled Loose Cellulose Attic Insulation

Why: Heat rises, so near your ceiling the air is probably the warmest in your house (good reason for slow circulating fans in high ceiling houses, but that's another topic). If there's an attic above your ceiling it's probably a major conduit of heat loss in winter. Adding insulation to your attic is said to be one of the most cost-effective energy saving investments you can make. Typically the attic will also get very hot in summer, so insulating it will also greatly reduce cooling problems in summer.

My project: Soon after buying my 32 year old house in 1999, I realized the attic insulation was pathetically inadequate. This house has roof trusses and the original builders simply put a few inches of loose mineral (rock) wool in the spaces between the 2x4 rafters. 32 years of settling and blowing around left the remains of the rock wool in very scattered condition. Many spots were bare -- you could look right at the gypsum drywall of the ceiling below!

Extensive remodeling in this house involved new and replaced wiring, recessed ceiling lights, bathroom fans, etc. etc. that required much climbing around in the attic, over the rafters, displacing and replacing insulation. Obviously, I had to finish all those big projects before adding more inches of insulation in the attic. Therefore it was summer of 2002 before this job got done.

Choosing the method of adding insulation was easy. I wanted to leave the few inches of rock wool there -- it would be nasty to remove and why waste it? So, by far the quickest and cheapest method was to add more blown-in loose insulation. Recycled cellulose, made from old newsprint I think, with flame and bug retardent chemicals added, was the clear choice. You can actually rent machines to do this, buy the bags of material, and do it yourself. But it was cheap enough to hire a professional and I'm glad I did. They knew how to seal off the attic from living spaces below, had more powerful blowing machines than you can rent, and knew how to get even coverage. And it's a really dirty job.

The two fellows came one morning, did the whole attic and were gone by noon. I had about 1700 sq. feet of attic area, to which they added 6+ inches of blown cellulose for total cost of $668. The R-value of what they added is ~23, so my total ceiling R-value now is probably close to the recommended 30 for this area. I now have between 7-8 inches covering the entire attic.

cellulose blown insulation

Energy savings:I averaged my natural gas usage in therms for the 6 highest heating months (Oct - Mar) of 2000-2005 -- two winters before and three after attic was insulated. The average savings after insulating was 330 therms for the 6 heating months, approximately 1/3 of the total usage for those 6 months of the year (980 before, 650 after). Natural gas was pretty cheap in 2002-3, a little over $.50/therm, but has approximately doubled since then, though it spiked higher in 2005-06, it has come down a little since then. But at then current rates, my insulation project paid for itself in the beginning of third winter (fall '04-winter '05). At present gas price, the project would have paid for itself in the second winter.

depth approx 7-8"