Building Green: Energy Efficiency and Aesthetics From The Same Materials (Part 17)


Cellulose insulation in the hopper of the rented blowing unit. Cellulose is a recycled
material that is appropriate for green building.

Before I start to talk about insulating the ceiling, I want to make one additional comment on the windows. As a general rule, windows that are hinged on one side—and therefore open and close like a door—are better at preventing drafts and air leaks than windows that slide in a track. Sliding windows are more apt to let air leak in because the seal must be loose enough to allow the window to slide back and fourth easily, whereas hinged windows press against a gasket which creates a nice tight mechanical seal. With the windows in place, it is time to insulate the ceiling. For this house, blown-in cellulose insulation was used. This material is manufactured from recycled newspaper, so it's a terrific option for anyone who's building green. A small amount of boric acid or borax is added to the product as a fire retardant and bug repellent. Another environmentally-friendly alternative— which is also great for the do-it-yourselfer—is cotton batting. This material (which usually consists of denim fibers) utilizes approximately 85% pre- consumer waste.


The end of the blowing hose is directed into the space between the ceiling and roof.

For my ceiling, the cellulose, which was blown in at a thickness of fifteen to eighteen inches, gave me a rating of R-55. The code for this area is R-30. Insulating a home to the minimum code requirements means that you will pass your inspection, but just barely. It's like getting a D-minus in school instead of an F. You squeaked by, but it's nothing to brag about. By blowing in a little more insulation, your home will stay cooler in the winter and warmer in the summer (for the entire life of the building). The added cost for this home was just a few hundred dollars— insignificant compared to the overall cost and also the long-term energy savings.

Large bags of cellulose can be purchased from your local home-improvement center. These same stores also rent the blowing equipment for a reasonable daily rate. The advantage of blown-in insulation is that it seals all the nooks and spaces around the rafters, conduit and framing. Batt insulation can leave gaps that allow the exchange of air between the interior and the exterior, which greatly diminishes the energy-efficiency of the home.

One thing to keep in mind if you decide to install the dry insulation with a blower is that the process generates a lot of dust. You absolutely must wear a respirator mask and eye goggles if you take on this job yourself. Another consideration is that there will be some settling of the dry insulation over time, giving you a rating in certain areas of the house of R-50 instead of R-55. If you want to avoid the whole issue of the insulation settling, you can hire a contractor to use a wet-blown formula. The wet-blown formula sticks instantly to wherever it is blown and will not settle, even over time. Even vertical walls can be filled by blowing the insulation in from the side (before the inner wallboard is installed). There is no mess and someone else is doing the work. Of course it will cost more to hire a contractor, and I have to admit that blowing in the insulation ourselves was fun and satisfying, albeit a bit messy.

More next week on building this green home.

See also: Part 1, part 2, part 3, part 4, part 5, part 6, part 7, part 8, part 9, part 10, part 11, part 12, part 13, part 14, part 15 and part 16.

[This has been a guest post by Ted Owens, a green designer and filmmaker. More details on green building design and construction can be found on his website and in the Building with Awareness DVD and Guidebook. -Ed.]

Tags: Architecture | Energy Efficiency