Help me understand home insulation
Greening your home is a series of decisions that will test your ability to weigh cost versus benefit. Decisions don’t come easy when trying to green an existing home. Most are drafty by nature, and every action you take to shore them up comes with an equal reaction, warns green building guru Jim LaRue.
This “good-news-bad-news” scenario plays out in every home weatherization project, but that doesn’t mean you should chuck the whole lot and head to Bermuda. You just have to be smart about how your priorities stack up.
If you’ve had a blower door test or put your own burning incense stick in front of your windows and can see air pouring through chances are double-paned, argon-filled, low-e glass replacements will benefit you (but not as much as you think, because the energy savings makes the payback on windows decades rather than years. Oh, and make sure your contractor blows in or uses aircrete foam insulation when they replace the weight cavities in old double-hung windows – don’t let them get away with shoving a little insulation down there with a screwdriver.). Better yet, invest about $40 to insulate your attic and around your chimney first.
LaRue has lots to say about “greening” your exterior walls, which inevitably leads to blowing cellulose insulation into the walls in older homes. The first question he gets is, with “knob-and-tube” wiring, is it a fire hazard? It can be, LaRue says (a sentiment shared by contractors). That said, the Ohio building code covering electrical allows for cellulose insulation if a certified electrician tests and confirms that all wires are properly connected to the fuse box. Still a fire hazard might exist at the splices of the wire, he says, even though most were done around the knobs to minimize the risk. The best bet is updating all the wiring before blow-in insulation (a costly operation, says LaRue, who is having his home rewired.). Cellulose blow-in insulation is a ‘green’ option because it’s made from recycled newspaper, treated with boric acid for pest and moisture resistance.
Ideas to guide you about air flow and moisture in homes:
- In the winter, air is coming in through first floor windows and out through the windows on the second floor. In the summer, the air flow is reversed.
- Homes built before the 1930s are mostly “balloon” construction (studs go from basement to third floor), which creates an updraft or chimney effect moving warm air up to the third floor or attic. Blow-in insulation and rolls of insulation on the walls between crawl space and finished areas of third floor can slow warm air loss. In unfinished third floors, insulate between the floor joists.
- Fiberglass windows are a slightly greener option than vinyl windows, LaRue says. (More recyclable and potentially less toxic to produce. Available from a Toledo-area manufacturer).
The Office of Energy Efficiency of the Ohio Department of Development has a list of energy auditors
Some common air leakage spots:
- Electrical receptacles
- Openings from interior into attic
- Between floor joists
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