05 October 2006

Make your Home Warmer with a Blowjob

Is your house cold and drafty? Maybe it is not insulated. Drill a small hole between the studs in an out-of-the-way wall, and poke in a wire with a little hook on it. You can tell right away if there is insulation or not. Given the newness of your house, I would expect it was built with fiberglass rolled between the studs. If not, go for an insulation blowjob.

The insulation process is a matter of drilling 2" diameter holes more or less on center in the empty spaces between the studs. This can be done from the inside or outside. Ideally, each cavity should have one high hole (about 1 foot below the top plate) and one low hole (about 3 feet above the floor). If you have old lathe & plaster walls that eat up conventional hole saws, invest in a carbide tipped style for about $20. Then, it's time for the blow job.

For insulation material, one can buy a number of different materials including cellulose (recycled newspapers) and fiberglass. We chose cellulose because at $7 per bale it is far cheaper than glass, and it is also environmentally friendly and much less hazardous to your lungs. The blow job is very messy, and even with a respirator you breathe a lot of crap.

Using a hasty formula I estimated it would take 25 bales to do my house. Because of our high ceilings, full 4-inch wall cavities, and a few unexpected things we ended up using 38 bales.
Before the blow job, we stuffed all the holes with pieces of fiberglass insulation. This prevents surprise blow outs when adjoining wall cavities are open.

My neighbor borrowed his boss's truck with a large hopper, screw, and air compressor machine--all driven by a small auto engine. The bales are unwrapped and dumped into the hopper and they emerge with lots of air through a 4-inch hose. The feed rate is variable, and set so that you have a good balance between how long it takes to fill the cavity and having lots of air move through the hose. If you get impatient, the hose clogs with insulation and it takes about an hour to take the sections apart and unclog them one-by-one.

The hose reaches into the house, and at the end reduces to a 2-inch diameter nozzle. The nozzle swivels and is directional, allowing the blower guy to direct it down, to the sides, and up. The idea of course is to completely fill the cavity. The material will move through a gap of 1/2 inch or less and occasionally comes out unexpected places--like a built in kitchen cupboard, or into the attic or basement, or into a porch roof cavity. You need to be sure that all the spaces at the top and bottom of the cavity (soffits?) are sealed.

As the blowjob progresses, you fill hole-by-hole with a Styrofoam plug. Eventually, they should be mudded over, hidden with a decorative border, etc.

The effect of this insulation -- even in our mild weather of the past week -- is dramatic. The house is noticeably less drafty and holds its temperature much better at night.
[Some builder supply stores rent small portable insulation blowing machines. I think people use them mostly for attic fill. With their small hose and low power, I'm not sure how effective they would be for wall fill.]

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